Lesson 5: Appliances

Lesson 5: Appliances jls164 Thu, 04/26/2012 - 13:35

The links below provide an outline of the material for this lesson. Be sure to carefully read through the entire lesson before returning to Canvas to submit your assignments.

Introduction

Introduction mxw142 Mon, 05/09/2016 - 14:49

Welcome to Lesson 5!

Welcome to the Appliances lesson! This is the most important one for most students--most important in the sense that it can make a difference in both energy consumption and environmental protection because we use a lot of appliances at home. We use a lot of energy for these appliances. In this chapter we are going to learn the basic operating principles of most of the residential big ticket items, for example refrigerators, or water heaters. Water heaters are one of the most energy-consuming appliances. And we will talk about clothes washers and dryers. We are not going to look at how to do the laundry, but we are going to look at the basic operating principles. In other words, how these things really operate. What are all the things that govern energy consumption, and what are all the things we need to look for when we buy some of these appliances?

We'll also learn how to do a cost benefit analysis. To do that, we will learn how to read energy guide labels. Energy guide labels are the yellow, ugly looking labels on appliances that give you the amount of energy that a model consumes. So when you go shopping (I'm sure you are all going to do that with your significant others in a few years) you're going to compare different options. You are going to look at a couple of models -- 3, 4 or 5 models, and say, "Okay, this is better than this; this is worse than this," and so on.

What are the factors that go into comparing several models and picking the right one, both with respect to energy consumption and environment protection? I will show you what kind of information you can get from these energy guides and how these can be used to compare model A vs. model B. For example, model A may cost $1000 and Model B may cost $1500. What you are basically deciding is, is it worth it to pay $500 extra to get the benefits that this model will give? In other words, the more expensive model obviously "should" give you more features that you want, or it should give you energy savings in the long run -- for example, cutting your energy bill by $50 every month. So it's going to really take about 10 months to recover the $500 you are paying up front. This kind of analysis is basically called life cycle analysis--what it would cost to buy a piece of equipment and to operate that over its lifetime. And we do that calculation for two models and see, in the long run, that one model is going to be cheaper and environmentally friendlier than another model. So we are going to learn how to do that. That discussion will be very common for all the appliances, and this calculation of payback period is the key for most of this lesson as well as the lessons to come. We will also look at refrigerators and calculate the efficiency of these refrigerators and how to use the efficiency we need to calculate how much energy these things consume. We will do that with clothes washers and dryers.

From here on you will also encounter some acronyms and energy efficiency terms, so you will need to pay attention to those. And, as I told you, these calculations and the use of the energy guides are the most important concepts in this lesson.

Lesson 5 Objectives

Upon completing this lesson, you should be able to:

Explain the operating principles of day-to-day residential appliances
Read and use Energy Guide labels
Calculate life-cycle analysis of appliances
Recommend ways to save energy and money based on good operating practices

Questions?

If you have any questions, please post them to the General Course Questions forum in located in the Discussions tab in Canvas. I will check that discussion forum daily to respond. While you are visiting the discussion board, feel free to post your own responses to questions posted by others - this way, you might help a classmate!

Appliance Energy Consumption

Appliance Energy Consumption jls164 Thu, 04/26/2012 - 13:36

Most homes have a variety of appliances with a wide range of operating costs. Typical costs of operation of basic household appliances are shown in the graph below.

Typical energy costs for various appliances.

Text description of the energy cost image.

Item	Cost per year
Electric Blanket	$10
Home Computer	$11
Television	$15
Microwave Oven	$15
Dehumidifier	$33
Well Pump	$42
Aquarium/Terrarium	$50
Dishwasher	$51
Electric Cooking	$58
Freezer	$67
Waterbed Heater	$74
Clothes Dryer	$75
Washing Machine	$80
Refrigerator	$96
Pool Pump	$123
Spa (Pump and Heater)	$190

Credit: U.S. Department of Energy

Household appliances, cooking, and lighting consume 33% of the energy at home as shown in the pie chart below. Water heating (not included in the appliances) is the second largest energy expense after home heating and cooling. It typically accounts for about 14% of the utility bill.

Data table for the residential energy use pie chart.

Typical Residential Energy Use
Appliance	Consumption Percentage
Heating and cooling	44%
Lighting, cooking, and other appliances	33%
Water Heating	14%
Refrigerator	9%

Credit: Typical Residential Energy Use © Penn State is licensed under CC BY-NC-SA 4.0

Energy Guide Labels

Energy Guide Labels jls164 Thu, 04/26/2012 - 13:37

All major home appliances must meet the Appliance Standards Program set by the US Department of Energy (DOE). Manufacturers must use standard test procedures developed by DOE to prove the energy use and efficiency of their products. Test results are printed on yellow Energy Guide labels (pictured below) which manufacturers are required to display on many appliances. This label provides the necessary information to perform a Life Cycle Analysis when comparing different models.

Instructions: View detailed descriptions about the information found on Energy Guide labels.

Energy Guide Labels.

Text description of the energy guide label.

The image is a yellow rectangular energy guide label with black text, used to provide energy efficiency information. At the top, it features the heading "ENERGYGUIDE" with an arrow pointing downward, indicating important information about energy use. Below this are two sections: on the left, details such as “Refrigerator-Freezer,” “Automatic Defrost,” “Side-Mounted Freezer,” and “Through-the-Door Ice” are listed; on the right, “XYZ Corporation - Model ABC-L,” “Capacity: 23 Cubic Feet” is specified. In the center, a highlighted section titled “Estimated Yearly Operating Cost” shows a large bold figure of "$67," representing the annual cost. Below, a horizontal bar labeled “Cost Range of Similar Models” shows arange from $57 to $74. Below this section, “630 kWh Estimated Yearly Electricity Use” is prominently marked in bold with a white background. Additional notes surround the main content, explaining the details of the cost estimates, the significance of the cost range, and utility rates. A small ENERGY STAR logo is in the bottom right, indicating environmental benefits. Black dotted lines and text boxes aid in navigating the information.

Credit: Energy Guide Label by Federal Trade Commission

The Federal Trade Commission's Appliance Labeling Rule requires appliance manufacturers to put these labels on refrigerators, freezers, dishwashers, clothes washers, water heaters, furnaces, boilers, central air conditioners, room air conditioners, heat pumps, and pool heaters. The law requires that the labels specify:

the capacity of the particular model—for refrigerators, freezers, dishwashers, clothes washers, and water heaters;
the energy efficiency rating and the estimated annual energy consumption of the model—for air conditioners, heat pumps, furnaces, boilers, and pool heaters;
the range of estimated annual energy consumption, or energy efficiency ratings, of comparable appliances.

How to Use the Labels

A worksheet on how to use the labels in choosing a cost-effective and environmentally friendly appliance is given below.

How to Use Energy Labels
Part A - General Information
1. Are the appliances comparable in size and features?	Answer has to be yes
2. What is the price of the more energy- efficient model?	$ ________
3. What is the price of the less energy-efficient model?	$ ________
4. What is the price of electricity in your region?	$ ________ / kWh
5. How long do you expect to keep the appliance? What is the life of the Appliance?	________
PART B - Determining why you should buy an energy efficient model
1. Calculating the price difference:
2. Price of the more energy-efficient model	$ ________
3. Price of the less energy-efficient model	$ ________
4. Price Difference	$ ________
Determining the annual energy savings
1. Annual energy consumption of the less energy-efficient model	________ kWh
2. Annual energy consumption of the more energy-efficient model	________ kWh
3. Annual energy savings	________ kWh
Determining the savings
1. Annual energy savings	________ kWh
2. Annual monetary savings on energy (energy savings x price)	$ ________
3. Energy savings over the life time of the appliance	________ kWh
(Life in years x annual energy savings)
1. Cost of energy savings over life time of the appliance	$ ________
Determining the Pay Back Period
1. Price difference between the models	$ ________
2. Annual monetary savings on energy (energy savings x price)	$ ________
3. Pay Back Period (years to recover the additional investment )	$ ________
4. Monetary savings on energy over the lifetime	$ ________
5. Price Difference	$ ________
6. Total monetary benefit for choosing environmentally friendly appliance (4 – 5)	$ ________

Water Heaters

Water Heaters jls164 Thu, 04/26/2012 - 13:37

Heat is continuously flowing from the tank of the water heater and the pipes to the room because the water heater is always at a higher temperature than the surroundings (basement or garage). Thermal energy flows from high temperature to low temperature. Heat is lost whether you use water or not.

Like most appliances, water heaters have improved greatly in recent years. Today's models are much more energy efficient, and you will be able to purchase a more efficient water heater that will save you money on energy each month. The average life expectancy of a water heater is 13 years. Therefore, the initial purchase price should not be an important factor in selecting a water heater.

Costs of Water Heaters

Just like other appliances, there are two costs associated with water heaters - initial purchase price and operating costs. Water heaters typically last for about 13 years, after which they need to be replaced. Also, each month, you pay for the fuel you use. An energy-efficient model could save hundreds of dollars in the long run in the energy costs and may offset the higher initial purchase price.

It can be compared to automobile mileage—some cars get 15 miles to a gallon, while other, more efficient, vehicles can go 30 miles or more on a gallon of gas. In the same way, some water heaters use energy more efficiently.

One should buy an energy-efficient water heater and spend less money each month to get the same amount of hot water.

Typical Water Use at Home

The table below shows typical water use for various purposes at home.

Typical Water Use
Use	Gallons per use
Shower	7-10
Bath (standard tub)	20
Bath (whirlpool tub)	35-50
Clothes washer (hot water wash, warm rinse)	32
Clothes washer (warm wash, cold rinse)	7
Automatic dishwasher	8-10
Food preparation and cleanup	5
Personal (hand-washing, etc.)	2

Energy costs increase with water temperature. Dishwashers require the hottest water of all household uses, typically 135ºF to 140ºF. However, these devices are usually equipped with booster heaters to increase the incoming water temperature by 15ºF to 20ºF. Setting the water heater between 120ºF and 125ºF and turning the dishwasher’s booster on should provide sufficiently hot water while reducing the chances for scalding.

Energy Required for Water Heating

Energy Required for Water Heating jls164 Fri, 04/27/2012 - 11:43

The amount of energy required to heat water is proportional to the temperature difference of what?

To calculate the Heat Required, use this equation:

$Q = m \times C_{p} \times ΔT$

Where …

$m$ = mass of water heated

$C_{p}$ = the heat capacity of water (1 BTU / lb ºF)

$ΔT$ = temperature difference.

Remember to make your units of measurements consistent. Since C_p is measured in pounds, your mass of water heated should be measured in pounds as well. Thus, if you only know the number of gallons, you must convert it into pounds. One gallon of water = about 8.3 pounds, so multiply number of gallons by 8.3 to determine the weight in pounds.

Example 1

It is estimated by the United States Department of Energy that a family of four, each showering for 10 minutes a day, consumes about 700 gal of hot water a week. Water for the showers comes into the home at 55ºF and needs to be heated to 120ºF.

To calculate the heat required, determine the variables:
m = mass of water heated = 700 gallons = 5810 lbs
C_pis the heat capacity of water = 1 BTU/lb ºF (given)
ΔT = temperature difference = 120 ºF – 55 °F

Heat energy required to heat 700 gal can be calculated as follows:

Heat Required = 5,810 lbs × 1 BTU/lb ºF × (120 ºF – 55 ºF)
Heat Required = 5,810 lbs × 65 ºF
Heat Required = 377,650 BTU/week

The heat requirement for one year is :

377,650 BTU/Week × 52 Weeks/Year = 19,637,800 BTU/year or 5,755 kWh

Assuming that the natural gas costs $10/MMBTU (1 MMBTU = 1,000,000 BTU) and electricity costs 0.092 per kWh, the gas costs would be $196.37 while electric costs would be $529.46. Clearly, electric heat is more expensive than natural gas.

Example 2

Estimate the % energy savings of an electric water heater that heats 100 gallons of per day when the temperature is set back at 110° instead of 120°F. The basement is heated and is at 65°F. The life of the water heater is expected to be about 10 years. Use an appropriate cost for electricity and compare the operating expenses.

Heat required (BTU) = m × C_p × (Temperature Difference)

Where C_p is the heat capacity of water (1 BTU/lb ºF) and m is the mass of the water (Assume 1 gal has 8.3 lb of water and the 3,412 BTU = 1 kWh)

Solution:

Energy required for heating the water to 120°F:

$= m \times C_{p} \times ΔT$

$= \underset{m}{\underset{︸}{\frac{100 gal}{day} \times \frac{8 .3 lb}{gal}}} \times \underset{C_{p}}{\underset{︸}{\frac{1 BTU}{lb °F}}} \times \underset{ΔT}{\underset{︸}{(120 - 65) °F}}$

$= \frac{100 gal}{day} \times \frac{8 .3 lb}{gal} \times \frac{1 BTU}{lb °F} \times (120 - 65) °F$

$= 45,650 BTU/day$

In a year the energy required is:

$\frac{45,650 BTU}{day} \times \frac{365 days}{year} = 16,662,250 BTUs per year$

In a 10-year period, the energy required is 166,622,500 BTU which is equal to 48,834 kWh.

$166,622,500 BTU \times \frac{1 kWh}{3,412 BTU} = 48,834 kWh$

Operating cost over its lifetime is:

$\frac{48,834 kWh}{1} \times \frac{$0 .09}{kWh} = $4,395.06$

Energy required for heating the water to 110°F:

$= m \times C_{p} \times ΔT$

$= \underset{m}{\underset{︸}{\frac{100 gal}{day} \times \frac{8 .3 lb}{gal}}} \times \underset{C_{p}}{\underset{︸}{\frac{1 BTU}{lb °F}}} \times \underset{ΔT}{\underset{︸}{(110 - 65) °F}}$

$= \frac{100 gal}{day} \times \frac{8 .3 lb}{gal} \times \frac{1 BTU}{lb °F} \times (110 - 65) °F$

$= 37,350 BTU/day$

In a year, the energy required is:

$\frac{37,350 BTU}{day} \times \frac{365 days}{year} = 13,632,750 BTUs per year$

In a 10-year period, the energy required is 136,327,500 BTU which is equal to 39,995 kWh .

$136,327,500 BTU \times \frac{1 kWh}{3,412 BTU} = 39,995 kWh$

Operating cost over its lifetime is:

$\frac{39,955 kWh}{1} \times \frac{$0 .09}{kWh} = $3,595.95$

Estimated % Energy Savings:

$$4,395.06 - $3,595.95 = $799.11 savings$

$\frac{$799.11}{$4,395.06} = 18.2% savings$

Types of Water Heaters: Storage or Tank

Types of Water Heaters: Storage or Tank jls164 Fri, 04/27/2012 - 12:43

There are several types of water heaters that are available on the market:

Storage or tank
On demand
Heat pump
Tankless coil
Indirect
Solar

However, most water heaters use a storage tank type.

Storage or tank-type water heaters are relatively simple devices and by far the most common type of residential water heater used in the United States. They range in size from 20 to 80 gallons, and can be fueled by electricity, natural gas, propane, or oil.

Parts of an Electric Hot Water Heater

Description of the parts of an electric water heater - Cold water valve, Electric supply, Temperature and pressure relief valve, Overflow pipe, Anti-Corrosion anode, Dip tube, Upper element, Lower element, Drain valve, Upper thermostat, Lower thermostat

Electric Hot Water Heater

Credit: © Penn State is licensed under CC BY-NC-SA 4.0

Parts of a Gas Hot Water Heater

Description of the parts of a gas water heater - Outlet to chimney, Flue, Cold water valve, Draft-diverter, Temperature and pressure relief valve, Overflow pipe, Anti-Corrosion anode, Dip tube, On/Off pilot, Shutoff valve, Temperature control, Gas supply, Drain valve, Thermocouple, Burner Air shutter

Gas Hot Water Heater

Credit: © Penn State is licensed under CC BY-NC-SA 4.0

How a Gas Hot Water Heater Works

When you turn on a hot water faucet or use hot water in a dishwasher or clothes washer, water pipes draw hot water from the tank. To replace that hot water, cold water enters the bottom of the tank, ensuring that the tank is always full. Depending on the type of fuel that is used, either electrical heating elements or a natural gas burner is used to heat the water.

Click the “play” button on the animation below to see how a gas hot water heater works. (41 seconds)

How a Gas Hot Water Heater Works

Text description of the How a Gas Hot Water Heater Works animation.

First, cold water flows in from the cold inlet tube into the bottom of the tank. A gas burner underneath the tank then heats the water to the desired temperature. The hot water exits through the warm outlet tube at the top to be distributed through the house, while the exhaust from the gas burner escapes through the chimney in the center of the tank.

Credit: Dr. Sarma Pisupati © Penn State is licensed under CC BY-NC-SA 4.0

Electric water heaters are generally less expensive to install (purchase price) than gas-fired types because they don't require gas lines and vents to let the combustion products out of the house. In previous lessons, and in Home Activity 2, we have seen that natural gas costs about 7–12 dollars per million BTUs, whereas electrical energy is 20–25 dollars per million BTUs, making electric water heaters more expensive to operate.

Storage tank-type water heaters raise and maintain the water temperature to the temperature setting on the tank (usually between 120°–140°F). Because the water is constantly heated and kept ready for use in the tank, heat energy can be lost even when no faucet is on. This is called standby heat loss. These standby losses represent 10 to 20 percent of a household's annual water heating costs. Newer, more energy-efficient storage models can significantly reduce the amount of standby heat loss, making them much less expensive to operate.

Types of Water Heaters: Demand Water Heaters

Types of Water Heaters: Demand Water Heaters jls164 Tue, 11/06/2012 - 13:38

Demand Water Heaters do not have storage tanks, so there is no standby heat loss from the tank, and energy consumption is reduced by 20 to 30 percent. Demand water heaters are available in propane (LP), natural gas, or electric models.

In these types of water heaters, cold water travels through a pipe into the unit, and either a gas burner or an electric element heats the water only when needed. With these systems, you never run out of hot water. However, the flow rate is limited by the outlet temperature.

The appeal of demand water heaters is the elimination of the tank standby losses, the resulting lower operating costs, and the fact that the heater delivers hot water continuously.

How a Demand Water Heater works

Click the “play” button to see how a Demand Water Heater works.

Text description of the How a Demand Water Heater Works animation.

Cold water flowing into the building is split off to a cold water line and a hot water line. When a faucet is turned on, water flows through the hot water line past has a heating unit where several heating elements quickly raise the water's temperature. The now hot water flows back into the hot water line and travels to where it is needed.

Dr. Sarma Pisupati

Typically, demand heaters provide hot water at a rate of 2 to 4 gallons per minute. This flow rate might meet the requirements of a household's hot water needs as long as the hot water is not needed in more than one location at a time (e.g., one cannot shower and do the laundry simultaneously). To meet hot water demand when multiple faucets are being used, demand heaters can be installed in parallel sequence.

Although gas-fired demand heaters tend to have higher flow rates than electric ones, they can waste energy even when no water is being heated if their pilot lights stay on. However, the amount of energy consumed by a pilot light is quite small. Thus, in most cases, gas demand water heaters will cost less to operate than electric water heaters.

Demand water heaters cost more than conventional storage tank-type units. Small point-of-use heaters that deliver 1 to 2 gallons per minute (gpm) sell for about $200. Larger gas−fired demand units that deliver 3 to 5gpm cost $550 - $1,000. The more hot water the unit produces, the higher the cost.

Advantages and Disadvantages of Demand Water Heaters

Advantages and Disadvantages of Demand Water Heaters
Advantages	Disadvantages
Compact in size Virtually eliminates standby losses Wastes less water because warm water is provided immediately where it is used (no need to wait for water to warm up) Provides unlimited hot water as long as it is operated within its capacity Equipment life is longer (20 years vs. 10-15 years for tank-type heaters) than tank-type heaters because they are less subject to corrosion	Demand water heaters usually cannot supply enough hot water for simultaneous uses such as showers and laundry. Unless your demand system has a feature called modulating temperature control, it may not heat water to a constant temperature at different flow rates. That means that water temperatures can fluctuate uncomfortably—particularly if the water pressure varies wildly in your own water system. Electric units will draw more instantaneous power than tank-type water heaters. If electric rates include a demand charge, operation may be expensive. Electric demand water heaters require a relatively high electric power draw because water must be heated quickly to the desired temperature. Make sure your wiring is up to the demand. Demand gas water heaters require a direct vent or conventional flue. If a gas-powered unit has a pilot light, it can waste a lot of energy.

Types of Water Heaters: Solar Water Heaters

Types of Water Heaters: Solar Water Heaters jls164 Tue, 11/06/2012 - 13:39

An estimated one million residential and 200,000 commercial solar water-heating systems have been installed in the United States. Although there are a large number of different types of solar water-heating systems, the basic technology is very simple.

Sunlight strikes and heats an "absorber" surface within a "solar collector" or an actual storage tank. These roof-mounted solar heaters supply about 80% of the hot water for the home. Either a heat-transfer fluid or the actual potable water to be used flows through tubes attached to the absorber and picks up the heat from it. (Systems with a separate heat-transfer-fluid loop include a heat exchanger that then heats the potable water.) The heated water is stored in a separate preheat tank or a conventional water heater tank until needed.

If additional heat is needed, it is provided by electricity or fossil-fuel energy by the conventional water-heating system.

A roof mounted solar water heater.

Credit: Thermodynamic Panels Installed by KVDP from Wikimedia (Public Domain)

How a Solar Water Heater Works

Click the “play” button to see how a solar water heater operates.

Text description of the How a Solar Water Heater Works animation.

Cold water is pumped to the solar collector on the roof of the house, where it is warmed by sunlight. The warm water then travels down into a storage tank and then to a conventional water heater. The water is heated further and becomes hot and available for use.

Dr. Pisupati

By reducing the amount of heat that must be provided by conventional water heating, solar water-heating systems directly substitute renewable energy for conventional energy, reducing the use of electricity or fossil fuels by as much as 80%.

Today's solar water-heating systems are proven reliable when correctly matched to climate and load. The current market consists of a relatively small number of manufacturers and installers that provide reliable equipment and quality system design.

A quality assurance and performance-rating program for solar water-heating systems, instituted by a voluntary association of the solar industry and various consumer groups, makes it easier to select reliable equipment with confidence.

Building owners should investigate installing solar hot water-heating systems to reduce energy use. However, before sizing a solar system, water-use reduction strategies should be put into practice.

Types of Solar Hot Water Heaters

There are five types of solar hot water systems:

Thermosiphon Systems. These systems heat water or an antifreeze fluid, such as glycol. The fluid rises by natural convection from collectors to the storage tank, which is placed at a higher level. No pumps are required. In thermosiphon systems, fluid movement, and therefore heat transfer, increases with temperature, so these systems are most efficient in areas with high levels of solar radiation.
Direct-Circulation Systems. These systems pump water from storage to collectors during sunny hours. Freeze protection is obtained by recirculating hot water from the storage tank, or by flushing the collectors (drain-down). Since the recirculation system increases energy use, while flushing reduces the hours of operation, direct-circulation systems are used only in areas where freezing temperatures are infrequent.
Drain-Down Systems. These systems are generally indirect water-heating systems. Treated or untreated water is circulated through a closed loop, and heat is transferred to potable water through a heat exchanger. When no solar heat is available, the collector fluid is drained by gravity to avoid freezing and convection loops, in which cool collector water reduces the temperature of the stored water.
Indirect Water-Heating Systems. In these systems, freeze-protected fluid is circulated through a closed loop and its heat is transferred to potable water through a heat exchanger with 80 to 90 percent efficiency. The most commonly used fluids for freeze protection are water-ethylene glycol solutions and water-propylene glycol solutions.
Air Systems. In this indirect system, the collectors heat the air, which is moved by a fan through an air-to-water heat exchanger. The water is then used for domestic or service needs. The efficiency of the heat exchanger is in the 50% range.

Direct-circulation, thermosiphon, or pump-activated systems require higher maintenance in freezing climates. For most of the United States, indirect air and water systems are the most appropriate. Air solar systems, while not as efficient as water systems, should be considered if maintenance is a primary concern since they do not leak or burst.

Types of Water Heaters: Heat Pump Water Heaters

Types of Water Heaters: Heat Pump Water Heaters jls164 Tue, 11/06/2012 - 13:40

Heat pumps are a well-established technology for space heating. The same principle of transferring heat is at work in heat pump water heaters (HPWHs) except that they extract heat from air (indoor, exhaust, or outdoor air) and deliver it to water. Some models come as a complete package, including tank and back-up resistance heating elements, while others work as an adjunct to a conventional water heater.

The simplest HPWH is the ambient air-source unit, which removes heat from surrounding air, providing the additional benefit of space cooling. Exhaust air units extract heat from a continuously exhausted air stream and work better in heating-dominated climates because they do not cool ambient air. Some units can even be converted between the two modes of operation for optimum operation in either summer or winter.

In mild climates, you can place ambient air-source units in unheated but protected spaces such as garages, essentially using outdoor air as a heat source.

Because it extracts heat from air, the HPWH delivers about twice the heat for the same electricity cost as a conventional electric resistance water heater.

Parts of a Heat Pump Water Heater (HPWH)

Heat Pump Water Heater Parts

Credit: © Penn State is licensed under CC BY-NC-SA 4.0

Desuperheaters

The Desuperheater feature is available on some central air conditioners and is a variation of the stand-alone HPWH. It provides economical supplemental water heating as a byproduct of air conditioning.

Desuperheater water heating can be part of an integrated package with a heat pump or air conditioner system. In most such systems, the heat pump water heating only occurs during normal demand for space conditioning, with resistance electric coils providing water heating the rest of the time.

During the cooling season, the Desuperheater actually improves the efficiency of the air conditioning system while heating water at no direct cost. In an average climate, a desuperheater might meet 20 to 40 percent of annual water heating demand.

Heat pump water heaters can provide up to 60 percent energy savings over conventional water heaters.

How a Heat Pump Water Heater Works

The Heat Pump Water Heater (HPWH) consists of three circuits. The HPWH consists of three circuits. Watch the video below to learn more about how a HPWH works. (30 seconds)

Click here for a text description of How a Heat Pump Water Heater Works

How a Heat Pump Water Heater Works

The heat pump water heater (HPWH) consists of three circuits; a Heat Pump circuit, a Geothermal Heat circuit, and a Desuperheater circuit.

The Heat Pump circuit consists of an indoor coil, a compressor, and a Desuperheater. Cool water flows from the indoor coil to the compressor. The water becomes heated as it travels through the compressor to the Desuperheater. The heat from the water is transferred to the water in the Desuperheater circuit through the adjacent coils.

The cool water then flows to the coils adjacent to the Geothermal Heat circuit and becomes heated as it flows back to the indoor coil.

The Geothermal heat circuit consists of a geothermal unit in the ground, a "from earth connection," and a "to earth connection." Water warmed by the earth flows from the "from earth connection" through the coils adjacent to the Heat Pump circuit, transferring the heat energy. The cool water flows back into the geothermal unit in the ground.

The Desuperheater circuit consists of the hot water tank that supplies water to the house and a set of coils adjacent to the Desuperheater coils in the Heat Pump circuit. The water from the tank cycles through the coils and is heated by the Heat Pump circuit.

Credit: Dr. Sarma Pisupati © Penn State is licensed under CC BY-NC-SA 4.0

Note: The concept shown in the animation is applicable to all HPWH: heat is picked up and delivered into some source – which could either be the ground, air, or water.

Most of the heat delivered to the water comes from the evaporator of the unit, not through the electrical input to the machine. Consequently, the efficiency of the HPWH is much higher than for direct-fired gas or electric storage water heaters.

The installed cost of commercial HPWH systems is typically several times that of gas or electric water heaters; yet the low operating costs can often offset the higher total installed cost, making the HPWH the economic choice for water heating.

The HPWH becomes increasingly attractive in building applications where energy costs are high, and where there is a steady demand for hot water. This attractiveness is less a function of building type than it is of water demand and utility cost.

Energy Efficiency of Water Heaters

Energy Efficiency of Water Heaters jls164 Tue, 05/01/2012 - 14:28

The federal efficiency standards for water heaters took effect in 1990, assuring consumers that all new water heaters meet certain minimum-efficiency levels. New standards, which took effect in January 2004, will increase the minimum efficiency levels of these products.

Water heater efficiency is reported in terms of the energy factor (EF). EF is an efficiency ratio of the energy supplied in heated water divided by the energy input to the water heater, and it is based on recovery efficiency, standby losses, and cycling losses. The higher the EF, the more efficient the water heater.

Electric resistance water heaters have EFs ranging from 0.7 and 0.95.
Gas water heaters from 0.5 and 0.6, with some high-efficiency models ranging around 0.8.
Oil water heaters from 0.7 and 0.85.
Heat-pump water heaters from 1.5 to 2.0.

There is little difference between the most efficient electric resistance storage water heaters and the minimum-efficiency standard that will take effect in January 2004. If you need to rely on electricity to heat your water, keep your eye out for the further development of heat-pump water heaters. This technology uses one-third to one-half as much electricity as a conventional electric resistance water heater.

Energy Efficiency Recommendations

Everything else being equal, select a water heater with the highest energy factor (EF). Below is a table with energy efficiency recommendations.

Water Heater Energy Efficiency Recommendations
Storage Type	Recommended		Best Available
Storage Type	Size	Energy Factor	Annual Energy Use (kWh)	Energy Factor	Annual Energy Use (kWh)
Less than 60 gallons	0.93	4,721	0.95	4,622
60 gallons or more	0.91	4,825	0.92	4,773

The higher the EF, the more efficient the water heater.

Other Considerations

In addition to EF, also look for a water heater with at least one-and-a-half inches of tank insulation and a heat trap.

In addition, capacity of a water heater is an important consideration. The water heater should provide enough hot water at the busiest time of the day. For example, a household of two adults may never use more than 30 gallons of hot water in an hour, but a family of six may use as much as 70 gallons in an hour.

The ability of a water heater to meet peak demands for hot water is indicated by its "first hour rating." This rating accounts for the effects of tank size and the speed by which cold water is heated. Water heaters must be sized properly. Over-sized water heaters not only cost more but increase energy use due to excessive cycling and higher standby losses.

Life Cycle Analysis

Life Cycle Analysis jls164 Fri, 05/25/2012 - 11:52

Let’s use the Energy Guide to perform a life-cycle analysis to help choose a water heater. Different models of water heaters with the same capacity can vary dramatically in the amount of electricity they use.

Instructions: Use the two EnergyGuide Labels for the different water heaters, to answer questions 1-8.

EnergyGuide Label for the $388.00 Water Heater

Click here to open a text description comparing the two Energy Guide Labels.

Compare the Two EnergyGuide Labels

Water Heater #1:

Water heater: Electric
Capacity (first hour rating): 58 gallons
This model uses 4622 kwh/year
Energy use range of all similar models (kwh/year): 4624 (uses least energy) - 5109 (uses most energy)
This model's estimated yearly operating cost is $388
Based on a 1994 U.S. Government national average cost of $0.0841 per kWh for electricity. Your actual operating cost will vary depending on your local utility rates and your use of the product.
Sold for $380

Water Heater #2:

Water heater: Electric
Capacity (first hour rating): 58 gallons
This model uses 4989kwh/year
Energy use range of all similar models (kwh/year): 4624 (uses least energy) - 5109 (uses most energy)
This model's estimated yearly operating cost is $419
Based on a 1994 U.S. Government national average cost of $0.0841 per kWh for electricity. Your actual operating cost will vary depending on your local utility rates and your use of the product.
Sold for $335

Credit: © Penn State is licensed under CC BY-NC-SA 4.0

Compare the Two Models

Determine Savings

Determine the Pay Back Period

Still trying to figure out the payback period? The price difference between the two models was $45, and your annual monetary savings was $33.76. So after one year, you got back $33.76 out of the $45 extra you spent on the superior model. How much longer would it take you to get back the remaining $11.24? Since $11.24 is about a third of $33.76, it would take you about a third of a year. Thus, your payback period is 1.33 years.

Obviously, it pays to buy an energy-efficient water heater by saving $393.96. It also helps the environment by not using 4,771 kWh of electrical energy and thereby not emitting 9,652 lb of CO₂, 21 lb of NO_x, 75 lb of SO₂ and 1 lb of CO and particulate matter each and into the environment. See the individual’s power!

Water Heaters: Your “Power” in the Environmental Protection

Water Heaters: Your “Power” in the Environmental Protection jls164 Thu, 04/26/2012 - 13:38

Do as much cleaning as possible with cold water to save the energy used to heat water.
Check your faucets for leaks. They waste both water and energy!
Conserve hot water by installing water-saving showerheads. A new showerhead can save as much as $10 a year in water and energy.
Once your water is hot, insulate to help keep it that way. Wrapping exposed hot water pipes with insulation will minimize heat loss. So will installing an R-12 insulation blanket around your water heater, unless the manufacturer does not recommend it.
Reduce your water heater's temperature to 120 degrees Fahrenheit. That will produce plenty of hot water and still save energy. For homes with a dishwasher, a setting of 140 degrees is required to clean properly, but most of the new dishwashers have a built-in water temperature booster.
Many new water heaters have a "vacation" setting you can use to save energy if you're away for more than a few days. Turn the thermostat "down" or "off" when you're gone for more than three days.

Refrigerators

Refrigerators jls164 Thu, 04/26/2012 - 13:38

Refrigerators are heat movers, which move heat from a low temperature (inside the refrigerator) to a high temperature (outside the refrigerator into the kitchen). Heat movers do not produce any heat, but just move from one location to another. (Note: The animation has no audio and is fully described in the text below.)

Diagram showing how a Heat Mover works

Credit: © Penn State is licensed under CC BY-NC-SA 4.0

How Does a Refrigerator Work?

The principle of operation of a refrigerator is similar to an air conditioner. It moves the heat energy from inside to outside. There are four basic components in a refrigerator and their functions are as follows:

Expansion valve - A liquid refrigerant at high pressure flows through an expansion valve. As the refrigerant moves through the expansion valve, it moves from a high-pressure zone to a low-pressure zone. The decrease in pressure corresponds with a decrease in temperature.
Evaporator or heat exchanging pipes - A set of coiled tubes carrying the low pressure, expanded refrigerant. In the evaporator, the liquid refrigerant also expands and evaporates. The evaporation of liquid takes away heat, creating cold gas in the coils. The cold refrigerant flowing through the coils absorbs heat from the refrigerator. The food gets cold. However, the refrigerant warms up because of the absorption of heat.
Compressor - A device that pressurizes the warm refrigerant and makes it hot (hotter than the kitchen temperature). This hot refrigerant goes into the condenser.
Condenser or second heat exchanger coil - Located at the back of the refrigerator where it gives off the heat to the air in the kitchen.

Click the “play” button to learn how a refrigerator works.

How a refrigerator works

Text description of how a refrigerator works.

How a Refrigerator Works

Compressed liquid refrigerant passes through an expansion valve that reduces the pressure and, in turn, the temperature. The now cold liquid travels through a series of evaporator coils. As it travels through the coils, the liquid evaporates, drawing the heat energy needed for evaporation from the food in the fridge. This process leaves the food cold as the heat has been moved to the refrigerant.

The evaporated refrigerant passes through a compressor that raises the pressure and temperature of the refrigerant and turns it back into a liquid. The liquid dispenses the heat collected from inside the fridge through the condenser coils and then passes through the expansion valve again to repeat the process.

Credit: © Penn State is licensed under CC BY-NC-SA 4.0

Types and Features

There are four types of refrigerators: top-freezer (or top-mount), bottom-freezer (or bottom-mount), side-by-side, and built-in (as shown below).

Refrigerators also come in four size categories: small (7 to 9.9 cubic feet), medium (10 to 13.9 cubic feet), large (14 to 19.9 cubic feet), and extra large (20 to 29 cubic feet).

Three types of refrigerators. Top mounted (freezer on top), bottom mounted (freezer on bottom), and side by side (freezer next to refrigerator).

Types of Refrigerators: Top Mounted, Bottom Mounted, and Side-by-Side.

Credit: "GE Profile™ ENERGY STAR® 22.2 Cu. Ft. Stainless Steel-Wrapped Bottom-Freezer Drawer Refrigerator." GE Appliances. 2024.

Energy Efficiency of a Refrigerator

Energy Efficiency of a Refrigerator jls164 Mon, 05/07/2012 - 14:17

Most of the energy used by a refrigerator is used to pump heat out of the cabinet. A small amount is used to keep the cabinet from sweating, to defrost the refrigerator, and to illuminate the interior.

The efficiency of a refrigerator is based on the energy consumed per year for a given size. The efficiency of a refrigerator is expressed in volume cooled per unit electric energy per day. Volume is measured in cubic feet and electrical energy is measured in kilowatt-hours.

Refrigerator Efficiency = Volume Cooled (ft³) / Unit Electrical Energy per day (KWh)

The energy efficiency of refrigerators and freezers has improved dramatically over the past three decades. For example, the energy bill for a typical new refrigerator with automatic defrost and top-mounted freezer will be about 55 dollars / year, whereas a typical model sold in 1973 will cost nearly 160 dollars / year (almost three times the energy consumption).

The Department of Energy (DOE) standards set maximum allowable annual energy consumption for different sizes and classes of refrigerators. These Federal efficiency standards first took effect in 1993, requiring new refrigerators and freezers to be more efficient than ever before. A new set of stricter standards took effect July 1, 2001.

Energy Guide Labels

Refrigerators now come with an EnergyGuide label that tells you in kilowatt-hours (kWh) how much electricity a particular model uses in a year. The smaller the number, the less energy the refrigerator uses and the less it will cost you to operate.

Full-sized refrigerators that exceed the federal standard by 15% or more (and full-sized freezers that exceed it by 10%) qualify for the ENERGY STAR label.
Compact refrigerators and freezers must exceed the standard by 20% to qualify for ENERGY STAR.

Energy Guide Labels.

Text description of the energy guide label.

Credit: Energy Guide Label by Federal Trade Commission

ENERGY STAR qualified refrigerators provide energy savings without sacrificing the features you want. ENERGY STAR–qualified models have

High-efficiency compressors
Improved insulation
More precise temperature
More precise defrost mechanisms

These models also use at least 15% less energy than required by current federal standards, and 40% less energy than the conventional models sold in 2001.

Many ENERGY STAR qualified models include automatic ice-maker and through-the-door ice dispensers. Qualified models are also available with top, bottom, and side-by-side freezers.

What to look for in a Refrigerator

When selecting a refrigerator, remember the following:

Refrigerators with the freezer on either the bottom or top are the most efficient. Bottom freezer models use approximately 16 percent less energy than side-by-side models, and top freezer models use about 13 percent less than side-by-side.
Through-the-door ice makers and water dispensers are convenient and reduce the need to open the door, which helps maintain a more constant temperature; however, these convenient items will increase your refrigerator's energy use by 14 to 20 percent.
Mini-doors give you easy access to items most often used. The main door is opened less often, which saves energy.
Too large a refrigerator may waste space and energy. One that's too small can mean extra trips to the grocery store. Your best bet is to decide which size fits your needs, and then compare the EnergyGuide label on each, so you can purchase the most energy efficient make and model. (filling your refrigerator helps with efficiency, so long as it's not overfilled!)
A manual defrost refrigerator uses half the energy of an automatic defrost model, but must be defrosted regularly to stay energy efficient.
Refrigerators with anti-sweat heaters consume 5 percent to 10 percent more energy. Look for models with an "energy saver" switch that lets you turn down—or off—the heating coils (which prevent condensation).

Technology Improvements

The improvement in the energy efficiency over the past three decades is due to the:

addition of vacuum insulation panels around the freezer section to reduce heat transfer;
addition of polyurethane foam to the doors to double insulation thickness;
replacement of AC motors with more efficient DC motors;
replacement of automatic defrost control with an adaptive defrost that operates only when needed.

Refrigerators & Environmental Protection

Refrigerators & Environmental Protection jls164 Thu, 04/26/2012 - 13:39

Refrigerators: Your “Power” in the Environmental Protection

Keep your refrigerator or freezer at the following temperatures: 37–40°F for the fresh food compartment of the refrigerator, 0–5°F for the freezer section. Use a thermometer to check inside temperatures.
Regularly defrost manual-defrost refrigerators and freezers; don't allow frost to build up more than 1/4 inch.
Make sure your refrigerator and freezer door seals are airtight. Check the seal on door gaskets periodically by closing the door on a dollar bill. If it pulls out easily, you may need a new gasket.
Keep the doors closed as much as possible and make sure they are closed tightly.
To ensure proper cooling of its contents, don't crowd food items. Too many dishes obstruct air circulation.
Cover liquids and wrap foods stored in the refrigerator. Uncovered foods release moisture and make the compressor work harder.
Replace paper wrappings on food items with aluminum foil or plastic wrap. Paper is an insulator.
Consider turning off the butter conditioner, since it is a little heater inside your refrigerator.
Experiment with the "energy saver" switch in your refrigerator—it allows you to adjust the heating coil under the "skin" of the refrigerator (the purpose of the heating coils is to prevent condensation on your refrigerator).
Placement of the refrigerator is very important. Direct sunlight and close contact with hot appliances will make the compressor work harder. More importantly, heat from the compressor and condensing coil must be able to escape freely, or it will cause the same problem. Don't suffocate the refrigerator by enclosing it tightly in cabinets or against the wall. The proper breathing space will vary depending on the location of the coils and compressor on each model—something important to know before the cabinets are redesigned.
Regularly brush off or vacuum the refrigerator coils on the back or bottom of the unit.
Because most refrigerators reject heat from the bottom and/or back, they need adequate clearance to allow sufficient airflow. While no specific studies have been done to calculate the optimum clearance space, one general rule-of-thumb is to double the space recommended by manufacturers for refrigerator installation. Another rule-of-thumb is to allow 2 inches of air flow around the refrigerator.
Don't keep that old, inefficient fridge running day and night in the garage for those few occasions when you need extra refreshments. A 15-year-old refrigerator could cost \$100–\$150 per year.

Clothes Washers

Clothes Washers jls164 Thu, 04/26/2012 - 13:39

Clothes washers and dryers account for 10 percent of the residential energy consumption, with most of the energy consumed for hot water used for washing.

An estimated 85 percent to 90 percent of the energy is used for heating the water.
Relatively, 10 percent to 15 percent of the energy is used by the clothes washer itself to operate the motor and controls.

A typical household does nearly 400 loads of laundry a year, and each load in a conventional washer uses 40 gallons of water. Therefore, any reduction in energy consumption for clothes washing application would involve reduction in hot water use.

Types of Clothes Washers

The basic principle for cleaning clothes has remained unchanged—wet the garment, agitate it to loosen the dirt from the cloth fibers, and then use more water to rinse the dirt off. What has changed over the millennia is the method of agitation? Pounding garments with stones was common for several thousand years, and along the way someone also figured out that using heated water got out a lot more dirt.

Clothes washers come in two types: Horizontal axis (h-axis) or front loading and Vertical axis (v-axis) or top loading (shown below).

Horizontal axis (front loading) and a Vertical axis (top loading)

Credit: Energy Star

Most clothes washers produced for the U.S. consumer are vertical axis (v-axis) washers with a central agitator. While there are variations, most v-axis washers suspend the clothes in a tub of water for washing and rinsing.

As an alternative, the horizontal axis (h-axis) washer tumbles the wash load repeatedly through a small pool of water at the bottom of the tub to produce the needed agitation. This tends to reduce the need for both hot and cold water.

The h-axis washer, popular in Europe, has a very limited market share in the United States at present. Yet, estimates have shown that a large quantity of energy and water could be saved through the replacement of conventional v-axis washers with the h-axis design.

H-axis washer

H-axis or tumble-action machines repeatedly lift and drop clothes, instead of moving clothes around a central axis. H-axis washers also use sensor technology to closely control the incoming water temperature. To reduce water consumption, they spray clothes with repeated high-pressure rinses to remove soap residues rather than soaking them in a full tub of rinse water.

Click the "play" button to see how an H-axis washing machine works. (Note: The animation has no audio and is described in the text above.)

In a study conducted by Oak Ridge national Laboratory (ORNL) in 1998 for U.S. Department of Energy, it was found that, on average, the h-axis washer used 62.2 percent of the water used by the v-axis washer, and this yielded total water savings of 37.8 percent. Moreover, the average h-axis washer consumed 42.4 percent of the energy used by a typical v-axis washer in the study, resulting in energy savings of 57.6 percent.

Features of the h-axis washer include:

Auto temperature. The machine will mix hot and cold water to a preset "warm" and "cold" so that the water is warm enough for the detergent to dissolve and optimally perform. During the winter in many parts of the country, cold tap water can be too cold to wash your clothes well.
Water level settings. Some of the very high-end machines sense the amount of clothing and automatically adjust the water level, but all except the most basic machines offer at least four settings.
Capacity. If you have a large household or athletes who produce an astounding amount of laundry each week, a larger capacity machine is a must. The front loaders generally hold more because they don't have the agitator. A definite minus for the front loaders, however, is the actual loading because you have to bend over to put in the clothes. To minimize this fact, the machines and their matching dryers are often displayed in stores on a raised platform.

Energy Efficiency and Water Usage

Energy Efficiency and Water Usage jls164 Fri, 05/25/2012 - 12:35

Stricter new federal standards for clothes washers took effect in two stages. The first stage was in force as of January 2004. Then in 2007, the second stage further strengthened the standard. Three factors are used in determining the federal standards:

Energy Factor is a metric that was previously used to compare relative efficiencies of clothes washers. The higher the Energy Factor is, the more efficient the clothes washer is. For clothes washers, Energy Factor is calculated using the following formula:
$Energy Factor = 392 \times Volume ({ft}^{3}) / Annual Energy Use (KWh)$
Water Factor is the number of gallons per cycle per cubic foot that the clothes washer uses. The lower the water factor, the more efficient the washer is. So, if a clothes washer uses 30 gallons per cycle and has a tub volume of 3.0 cubic feet, then the water factor is 10.0. Note: the energy factor for washers does not indicate the real energy efficiency because of the tub size and other factors. Therefore, the Energy Factor is modified to include the tub size and drying characteristics.
Modified Energy Factor (MEF) is a new equation that replaced Energy Factor as a way to compare the relative efficiency of different units' clothes washers. MEF takes into account the amount of dryer energy used to remove the remaining moisture content in washed items.
${MEF = ft}^{3} /KWh/Cycle$

For more information about MEF circulation, please see the August 27, 1997 Federal Register entry regarding 10 CFR Part 430.

Clothes Washers & Environmental Protection

Clothes Washers & Environmental Protection jls164 Thu, 04/26/2012 - 13:39

Your “Power” in the Environmental Protection

Wash full loads—Clothes washers are most efficient when operated with full loads.
Wash clothes in cold water – It will conserve energy and is also recommended for colored and many delicate fabrics.

In addition:

Consider Front loaders – Since they use less water, they use less energy. The most efficient front loaders use less than half the amount of water used in the average top loaders.
Purchase washing machines with the Energy Star designation – They are 50 percent more energy efficient than the current minimal allowable standard.

Many new energy-efficient, water-conserving clothes washers have been introduced over the past few years. These resource-efficient washers are available in a variety of sizes and configurations, offering consumers a wide range of front-loading and top-loading styles in many different price ranges.

Clothes Dryers

Clothes Dryers jls164 Thu, 04/26/2012 - 13:40

A clothes dryer dries wet clothes in a rotating drum through which hot air is circulated.

The hot air removes the residual moisture from the clothes.
The humid air from the dryer is vented out of the house.
The drum is rotated with the help of a motor at relatively slow speeds to create a tumbling effect.

Clothes dryers can be of two types: electric and gas.

In an electric dryer, electrical energy is used for both the motor to rotate the drum and heating the air.
In a gas dryer, the motor requires electrical energy but the air is heated by natural gas.

Energy Efficiency of Dryers

Dryers work by heating and aerating clothes. The efficiency of clothes dryer is measured by a term called the Energy Factor. It is similar to the miles per gallon for a car, but in this case the measure is pounds of clothing per kilowatt-hour of electricity.

The minimum Energy Factor rating for a standard capacity electric dryer is 3.01. For gas dryers, the minimum energy factor is 2.67. The rating for gas dryers is provided in kilowatt-hours though the primary source of fuel is natural gas.

Unlike most other types of appliances, energy consumption does not vary significantly among comparable models of clothes dryers. Clothes dryers are NOT required to display EnergyGuide labels.

Clothes Dryers: Your “Power” in the Environmental Protection

Locate your dryer in a heated space. Putting it in a cold or damp basement will make the dryer work harder and less efficiently.
Make sure your dryer is vented properly. If you vent the exhaust outside, use the straightest and shortest metal duct available. Flexible vinyl duct isn't recommended because it restricts the airflow, can be crushed, and may not withstand high temperatures from the dryer.
Check the outside dryer exhaust vent periodically. If it doesn't close tightly, replace it with one that does in order to keep the outside air from leaking in. This will reduce heating and cooling bills.
Clean the lint filter in the dryer after every load in order to improve air circulation and reduce risk of fire. Regularly clean the lint from vent hoods.
Dry only full loads, as small loads are less economical; but do not overload the dryer.
When drying, separate your clothes and dry similar types of clothes together. Lightweight synthetics, for example, dry much more quickly than bath towels and natural fiber clothes.
Dry two or more loads in a row, taking advantage of the dryer's retained heat.
Use the cool-down cycle (permanent press cycle) to allow the clothes to finish drying with the residual heat in the dryer.
In good weather, hang clothes dry outside. This the ultimate energy saver for clothes drying

Dishwashers

Dishwashers jls164 Thu, 04/26/2012 - 13:41

A dishwasher typically uses the equivalent of 700–850 kilowatt-hours of electricity annually, or nearly as much energy as a clothes dryer or freezer. About 80 percent of this energy is used, not to run the machine, but to heat the water for washing the dishes.

Older dishwashers use about 8–14 gallons of water for a complete wash cycle.
Newer dishwashers, built in the past 10 years, have been using 7–10 gallons per cycle.

The dishwasher is the only device at home that requires a water heater temperature that is about 140°F. The units built recently have supplemental heaters in the dishwashers to bump up the temperature so that the main water heater temperature can be set at 120°F or less. Remember that each 10°F reduction in water heater temperature lowers the water heater energy cost by 3 percent to 5 percent.

How a Dishwasher Works

A dishwasher is essentially an insulated water tight box. The dirty dishes are systematically arranged in the dishwasher. As shown below, hot water is sprayed on to the dishes as jets. Repeated jets of water emanating from a spray arm clean the dishes. Some models have two spray arms: one at the bottom of the dishwasher (lower spray arm) and one at the top (upper spray arm). The dirty water passes through a filter and re-circulates until the dishes are finished. Fresh water is then spayed during the rinse cycle to remove the soapy water. Then the dishes are dried with either electric heat or simply with air.

Inside of a dishwasher

Inside of a dishwasher by Ryan from Louisville, USA is licensed under CC BY-SA 2.0

Press the “play” button to see how a dishwasher works. This is also described in the paragraph above. (Note: The animation has no audio.)

Features of a Dishwasher

Dishwashers can be built-in or portable. Built-ins are mounted under a kitchen countertop usually next to a sink. Portables are on wheels with finished tops and sides. Most models can be converted into under-counter mounting. However, because of the additional connection hardware and finished sides, portables usually cost more than similar built-in models.

Some of the additional features that are offered are:

Interior layout—configuration of sliding racks, baskets, and trays. Does the washing arm reduce the amount of loadable space?
Water heating—Most homes have water heaters set to 110 degrees. However, to clean well, a dishwasher should use water at 140 degrees. Many budget units now offer a water heating feature.
Number of cycles—light cycles, normal, heavy or pans, and rinse and hold to remove food if dishes will sit in the washer a while before the wash cycle is run.
Water-saving cycles—If you live in an area where fresh water is scarce, you’ll want to consider this feature.
Sound insulation—The sound level will vary from one model to another. Consider how important a quiet wash cycle is before you purchase.
Build in food disposers—will grind up food similar to in-sink units, allowing the user to spend less time cleaning dishes before they go into the dishwasher.
Controls—Entry-level machines feature knob and dial controls. On mid- to upper-end models, you will find push-button switches hidden behind smooth, one-piece, plastic console covers. Some of the highest priced dishwashers feature electronic touchpad controls with lighted displays for an uncluttered, high-tech look. And the highest-end European models now integrate controls on the top of the door so they can't be seen when the machine is closed.
- Countdown timer — lets you know how much time is left in a cycle.
- Clean light — signals that cycle is complete and dishes are clean.
- Soil sensors — take the guesswork out of cycle selection. Sensors optically analyze dirtiness of water and adjust water level and wash length accordingly.
- Delay-start — timer that allows starting dishwasher automatically; lets you take advantage of late-night off-peak power rates or run the dishwasher after everyone has taken a shower.
Color and Appearance—Does the dishwasher fit in your kitchen? Do you like its appearance?
Delay Start Timer—Allows the user to load the washer and have it start a few hours later.

Energy Efficiency and Test Criteria

Energy Efficiency and Test Criteria jls164 Fri, 05/25/2012 - 13:21

Energy Factor (EF) is the dishwasher energy performance metric. EF is expressed in cycles per kWh and is the reciprocal of the sum of the machine electrical energy per cycle, M, plus the water heating energy consumption per cycle, W.

Energy Factor (E F) = 1 / M + W

This equation may vary based on dishwasher features such as water-heating boosters or truncated cycles. The greater the EF, the more efficient the dishwasher is.

The EF is the energy performance metric of both the federal standard and the ENERGY STAR qualified dishwasher program. The federal EnergyGuide label on dishwashers shows the annual energy consumption and cost. These figures use the energy factor, average cycles per year, and the average cost of energy to make the energy and cost estimates. The EF may not appear on the EnergyGuide label.

Test Criteria for ENERGY STAR Qualified Dishwashers

Dishwasher manufacturers must self-test their equipment according to the new Department of Energy (DOE) test procedure defined in 10 CFR 430, Subpart B, Appendix C. This DOE test procedure was announced on August 29, 2003, and all models had to be tested using the new procedure by February 25, 2004.

This test procedure establishes a separate test for soil-sensing machines. Included in the final rule was a decision to add standby energy consumption to the annual energy and cost calculation, but not to the energy factor calculation. Also, the average cycles per year has been lowered from 264 cycles per year to 215 cycles per year. Energy Star dishwashers are at least 25 percent more energy efficient than minimum federal government standards.

The table below lists the standard and the ENERGY STAR approved dishwasher energy factors.

Energy Standards for Dishwashers
Product Type	Federal Standard Energy Factor	ENERGY STAR Energy Factor
Standard ( > 8 place settings + six serving pieces)	> 0.46	> 0.58
Compact (< 8 place settings + six serving pieces)	> 0.62	NA

The current ENERGY STAR criteria for dishwashers became effective January 1, 2001. This criteria of at least 25 percent above the federal standard and applies only to models manufactured after January 1, 2001. The previous ENERGY STAR criterion was 13 percent above the federal standard.

Dishwashers & Environmental Protection

Dishwashers & Environmental Protection jls164 Thu, 04/26/2012 - 13:41

Your “Power” in the Environmental Protection

Buying the correct size appliance for your needs is critical to saving money, energy, and water. In dishwashers, there are compact and standard-capacity units. Compact models use less energy and water per load, but you may actually consume more energy operating them more frequently. The following tips help you to save even more:

Avoid rinsing dishes before you load them in the dishwasher or, if you must rinse, use cold water.
Run your dishwasher with a full load. Most of the energy used by a dishwasher goes to heat water. Since you can't decrease the amount of water used per cycle, fill your dishwasher to get the most from the energy used to run it.
Avoid using the heat-dry, rinse-hold, and pre-rinse features. Instead, use your dishwasher's air-dry option. If your dishwasher does not have an air-dry option, prop the door open after the final rinse to dry the dishes.

Review and Extra Resources

Review and Extra Resources jls164 Thu, 04/26/2012 - 13:41

Review Sheet Lesson 5 – Appliances

Appliance energy consumption
Use Energy guide labels
- Should be able to calculate/perform
  - Annual energy savings when comparing two models
  - Payback period when comparing two models
  - Life cycle analysis when comparing two models
Water heaters
- Should be able to calculate energy required for heating water
- Gas vs. electric
- Types of water heaters (advantages and disadvantages)
  - Storage or tank
  - Type on demand
  - Heat pump
  - Tankless coil
  - Indirect
  - Solar
- Energy Efficiency of water heater
  - Energy Factor (EF)
- Environmental protection
Refrigerators
- How Does a Refrigerator Work? Function of:
  - Expansion valve
  - Evaporator
  - Compressor
  - Condenser
- Types of refrigerators
  - Top Mounted
  - Bottom Mounted
  - Side-by-side
- Energy Efficiency
- Environmental Protection
Clothes Washer
- Types
  - Horizontal Axis (front loading)
  - Vertical Axis (top loading)
- Efficiency
  - Energy Factor (EF)
  - Water Factor (WF)
  - Modified Energy Factor (MEF)
- Environmental Protection
Clothes Dryer
- Energy Efficiency
- Environmental Protection
Dish Washer
- How a Dishwasher works
- Environmental Protection

Test Yourself

The questions below are your chance to test and practice your understanding of the content covered in this lesson. In other words, you should be able to answer the following questions if you know the material that was just covered! If you have problems with any of the items, feel free to post your question on the unit message board so your classmates, and/or your instructor, can help you out!

Describe three operating practices in using refrigerators that can save energy and money.
List the five main components of a refrigerator, and explain how a refrigerator works.
Describe five ways in which you, with good operating practices, can reduce energy consumption of water heaters at home.
Explain the advantages and disadvantages between Storage and Demand water heaters.
What are the various methods in which solar energy can be collected for water heating?
What is EF? And how does it describe the efficiency of a water heater?
How do electric and gas compare for water heating?
Why are ENERGY STAR appliances better in terms of efficiency, and how can they help the environment?
What are Energy Guide Labels? What information can be obtained from these labels, and how can this information can be used to select an environmentally friendly appliance?
Briefly describe five ways in which we can save energy in using clothes washers and dryers.
Compare and contrast the v-axis (top loading) and h-axis (front loading) water heaters.
Explain how energy efficiency of clothes washers is evaluated.
What are good operating practices for clothes dryers?
How can you describe the energy efficiency of dishwashers?
Describe appliance-operating practices that can help the environment.
Calculate the amount of heat energy required to heat 200 lbs of water that is heated from 55 degrees F to 130 degrees F.
200 gal of water is heated in a heater from 60 degrees F to 120 degrees F every day by a family of four. What is the annual energy requirement?
An electric water heater heats 250 gallons of water per day from 58 degrees F to 140 degrees F. How many kWh of energy are required? Recall that, 3412 Btus =1 kWh.
If the temperature of the water heater was reduced to 120 degrees F, what percent of energy can be saved?
What is the cost of operating the water heater in Problem 3, if electricity cost is $0.08 per kWh?
A water heater heats 200 gal of water a day from 55 degrees F to 130 degrees F using natural gas. How many CCF of natural gas are required every month?
What would be the monthly cost of natural gas in problem 6?
What would be the monthly cost of energy if electricity was used for heating the water in problem 6?
If the temperature of the water heater was reduced to 120 degrees F in Problem 6, how many kWh could be saved and what would be the cost savings?
Estimate the % energy savings of an electric water heater that heats 100 gallons per day when the temperature is set back at 110 instead of 120 F. The basement is heated and is at 65 F. The life of the water heater is expected to be about 15 years.
- Use an appropriate cost for electricity, and compare the operating expenses with the approximate initial cost of the water heater (from the lectures).
- Heat required (BTUS) = m x Cp x (Temperature Difference)
- Where Cp is the heat capacity of water (1 Btu/lb/F)
- And m is the mass of the water (Assume 1 gal has 8.3 lb of water and the 3,412 Btus = 1 kWh)
An old refrigerator consumed 150 W of power. Assuming that the refrigerator operates for 20 hours in a day, what is the annual operating cost, assuming the cost of electricity to be $0.06 per kWh?
Suppose that an oven lasts for 10 years. For a given heating effect, the least efficient oven draws 1,000 W. The most efficient one uses 450 Watts. Assuming that the oven uses 700 W annually, and that the local energy cost is 0.06 per kWh, can you save any money? If so, how much money over its lifetime? If the more efficient oven costs $100 more than the least efficient one, would you buy the more efficient model?
Suppose you are comparing two refrigerators, both of which last for 10 years. The least efficient refrigerator draws 275 W of power. The most efficient one uses 250 Watts. Assuming that the refrigerator operates 4000 hours annually and that the local energy cost is 0.06 per kWh, can you save any money with the energy efficient model? If so, how much money over its lifetime? If the more efficient refrigerator costs $100 more than the least efficient one, would you buy the more efficient model?

Lesson 5 Deliverables

Lesson 5 Deliverables mxw142 Thu, 05/05/2016 - 18:18

Deliverable 1

You must complete a short quiz that covers the reading material in lesson 5. The Lesson 5 Quiz, can be found in the Lesson 5: Appliances module in Canvas. Please refer to the Calendar in Canvas for specific time frames and due dates.