What is it and how does it work?
Geothermal home systems are not geysers or hot springs. Rather, they take advantage of the consistent year round temperature of the ground, which is approximately 45-75 degrees Fahrenheit. By pumping water through this temperate ground layer, very cold water in the winter or very warm water in the summer can be brought to a medium temperature that requires less energy to either heat or cool.

How does geothermal home energy work?
The geothermal system acts as both a furnace and an air conditioning unit. It relies on the temperate water circulated through pipes deep in the ground to heat and cool air. It feels just like regular A/C but uses less energy that is clean and renewable.

How much does a geothermal system cost?
The average geothermal system can cost roughly $25,000, — depending on a number of different factors such as home size and climate.There are state and federal incentives that can cover up to 60% of the total system cost, and you’ll see 20-50% savings on your heating and cooling costs every month. Depending on your local climate, you may be able to achieve payback on your system in as little as three years.

Other Useful Web Resources
Pacific Gas & Electric SGIP CaliforniaGeo Comment: You will note the absence of geothermal heat pumps in the SGIP program.

Source: Energy Upgrade California, Geothermal Home Energy