7.2 Water Heaters
7.2 Water HeatersThink about all the places you use hot water in your life. Every time you shower, or wash your hands you are using energy to make that water hot. In this lesson we will learn about the most common types of hot water heaters available on the market.
Types of Water Heaters
In this lesson, you will learn about the main types of Water Heaters on the Market today. Here is a quick rundown of those types.
| Type | Quick Description |
|---|---|
| Storage Tank | Heats and stores water in an insulated tank (most common) |
| On-Demand / Tankless | Heats water only when you need it—no storage |
| Heat Pump (Hybrid) | Moves heat from the air into water (like a fridge in reverse) |
| Tankless Coil | Uses your home's boiler to heat water on-the-fly |
| Indirect | Uses a boiler + separate storage tank for higher efficiency |
| Solar | Uses sunlight + collectors to heat water (with backup system) |
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 7-13 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. In this lesson, we will be recalling our "Life Cycle Cost Calculations" that we learned back in Lesson 5 to compare the actual cost of heating hot water in our home.
Typical Water Use at Home
The table below shows typical water use for various purposes at home.
| Use | Gallons per use |
|---|---|
| Shower | 7-10 |
| Bath (standard tub) | 15-20 |
| Bath (whirlpool tub) | 35-50 |
| Clothes washer (hot water wash, warm rinse)** | 7-25 |
| Automatic dishwasher ** | 3-5 |
| 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.
**This is for modern (2020s) based appliances. If you are using an older dishwasher or clothes washer, your hot water usage may be much higher!