"For an average fuel oil homeowner in New York, switching to geothermal would save 110 tons of CO2 and $35,000 over 20 years," Hannun said. "For the average propane home, the homeowner would save over 130 tons of CO2 and $63,000 over 20 years," she said.

I'm smack in the middle of my geothermal internship, and funny to see this crop up. As I'm here I've learned HVAC is responsible for 32% of our carbon emissions in the US. As it turns out with both NY rebate and Federal tax credits, the system price is dropped by a third, and from there the system pays for itself within 3 years. Now, this system that Google intends to use is far and away not like to be anything like what I'm learning... but for a tidbit, one of the company's systems I'm with cost the owner only $65 in HVAC expenses last month, and that's the least efficient system; an updated system cost the owner $18.