Geothermal energy has already been proven to be a good alternative in some areas. Any alternative is a good alternative if it does not use up natural resources. Using geothermal solutions for small spaces is an ideal application for that form of energy but depending where you live the technology might not be efficient enough or ready to employ yet.
Geothermal energy can be used abundantly to heat homes in cold climates for decades or centuries. Space heating takes these pockets of heat and shunts them to certain areas and settlements. Places such as the Great Basin in the United States can benefit from geothermal heat found near Yellowstone National Park, the difficulty is getting that thermal energy to larger areas. If more people move to geologically active places, geothermal energy is a perfect source for winter heat.