Let us compare the way in which light is valued with the way that a metal ore (in this case, zinc). An ore is an unrefined rock composed of minerals, which contains a raw metal that is valued (say, zinc), but which must be processed to access that metal. The value of an unconverted photon is a variable quantity, much like the value of a mineral resource in a geologic formation. The value of any commodity varies with the demand for the good and the costs of alternatives.
In economics, the measured response (in the market) of how the quantity of a product in demand is changed by the incremental change in the price of that product is termed price elasticity of demand. The demand is considered elastic if a small change (like a decrease) in price leads to people demanding more of the product. The demand in considered to be inelastic if a large change (again, a decrease) in price does not lead to people demanding more of the product. The elasticity of demand for solar power will depend on a few general rules, and we will try to contain our examples to solar scenarios for a client or group of stakeholders.
First, one evaluates the availability of close substitutes for the particular SECS of interest. If the desired useful energy form or technology has many available close substitutes, then it will be easier for clients/stakeholders to switch among goods for the same desired feature, and the demand will tend to be elastic.