A: Biomass energy is energy that comes from organic material such as plants and animals. Biomass would include: ethanol from corn or grasses, biodiesel from soybeans or vegetable grease, methane from animal waste, or wood for burning in a stove. Solar energy is energy received directly from the sun. Solar energy could be electricity from collector panels on a roof, hot water from solar collectors that face the sun and circulate water through them, or the heat that enters homes through windows that face the sun. Geothermal energy is energy extracted from the earth. The center of the earth is very hot, and there are places on the earth where this heat is closer to the earth’s surface than others. In those places, holes have been drilled down and the extracted heat is used to generate electricity. There are also geothermal heat pumps which can be used almost anywhere on the earth to gather the earth’s heat for heating and cooling homes. In a sense, geothermal energy is also a form of solar energy because the earth stores some of the sun’s energy. The advantage of these three energy sources is that they are renewable. Renewable means we can grow more plants each year, the sun supplies energy whether it is used or not, and the earth's surface is continuously warmed by the sun. The disadvantage of these energy sources is that we have not yet found economical ways of extracting the energy from these sources. With biomass, in some cases, we have to use energy to produce the energy. In other cases for biomass, solar, and geothermal, it takes expensive equipment to extract the energy. More efficient ways of using these types of energy are also needed. How we use the energy from these sources, once we have gathered it, can be problematic. For more information on these types of energy, visit the following web sites:

• dec2004/www.eere.energy.gov/RE/bioenergy.html">Biomass: www.eere.energy.gov/RE/bioenergy.html
• dec2004/www.eren.doe.gov/RE/solar.html">Solar: www.eren.doe.gov/RE/solar.html
• dec2004/www.eere.energy.gov/RE/geothermal.html">Geothermal: www.eere.energy.gov/RE/geothermal.html

1. Set the temperature for the backup heat very low at zero degrees.
2. Wait for the temperature outside to become low enough that the heat pump will no longer keep up with the heating level you have set. You will know when this happens because the temperature inside your home will be less than the thermostat setting and the heat pump will have been running for more than 20 minutes.
3. Note the outside temperature when the heat pump could no longer keep up with the heating load.
4. Set the temperature for the backup heat to come on at one or two degrees above the outside temperature you noted in methods #2 or #3 (The outdoor temperature where the heat pump could no longer keep up with the heating load). Or, if you don't mind your home being a little cooler, set the temperature at or just below the temperature you noted.
5. If your home ever becomes colder than you would like because the heat pump is not keeping up, set the temperature for the backup heat several degrees higher: 20 to 22, or from 10 to 12.