Geothermal energy is heat stored in the earth. Much of the energy is stored form sunlight though geological fluctuations also play a large roll. Old faithful, the majestic geyser in
Yellowstone National Park, is perhaps the most recognized example of geothermal processes at work.
The earth is able to maintain a more consistent temperature than the air, because it absorbs 47% of the sun's energy. Geothermal systems tap into this energy with an "earth loop" which is essentially flexible piping buried around your home. With the use of pumps, Geothermal energy can be utilized to heat or cool your home efficiently. Click here to read more about Geothermal heat.
No matter what climate you live in, the temperature below ground stays fairly consistent all year. Geothermal systems are especially efficient here in the Pacific Northwest and most come with a 25 year warranty.