The sun's heat is free. But you can't heat your whole house with it - unless you harvest it from the earth with a geothermal heating and cooling system. Since it uses electricity only to transfer the heat from the earth to your home, a geothermal system can cut your heating bills by up to 70%. This remarkable system reverses the process to cool your home in summer. Find out how from your local contractor. And use our handy contractor guide to help you choose which contrator to use for your installation.