As we complete the cooling season here in Dallas, I am still pining for a geothermal heating and air-conditioning system. In some ways it's more compelling that a photovoltaic (PV) electricity system. Here's why....
Basically the system is a heat pump connected to holes in the ground. Heat pumps have been around for ages and are generally perceived as more efficient than regular AC compressors and furnaces. And more expensive to purchase and install.
What geothermal does is marry a high efficiency heat pump to a source for steady temperatures from the ground. We have local companies that do this by drilling deep but small diameter holes and running a plastic pipe to the bottom and back to form a ground loop (300 feet). Depending on the size of the system, (mine is five ton), they would drill one hole per ton.
They need 20 feet between each hole and they connect them all together and to a pump to circulate fluid to transfer the ground temperature to the pump. The ground is a steady 68 degrees all year round here in Dallas. This fluid is used to cool the air or warm the air in the heat pump. (It's actually way more complex, but that's the gist of it).
So on a hundred degree day the heat pump, (bad name), takes 68 degree water and uses it to cool the house rather than using a compressor to cool whatever the latest freon equivalent is... That's right, no compressor! No noise outside, no ugly box, no unreliable and expensive outside gear to make coolness.
On a chilly winter day, all the heat pump has to do is get the 68 degrees up to your thermostat setting using natural gas or electric. As a side benefit, you can also put your water heater in the loop so it isn't heating up colder water all the time.
All of this combines to save around 50% on heating and cooling costs per my contractor. Now my guess is your mileage may vary but...that's a huge amount! My AC compressor is rated at 14 SEER and the heat pump is around 27 SEER. The heat pump is a variable device meaning I could safely close off rooms and the heat pump adjusts its output without harm to itself.
50% of my heating and cooling bill would be around $1320 in electric and $450 in gas for a total of $1,770 savings a year. Now the bad news. The cost for the system is $36,000. There is a 30% federal tax credit that brings the price down to $25,200. That translates to a 14+ year payoff at today's utility rates. If I were forced to replace my current traditional system with a similiar system it would cost me $10,000, I know because my neighbor just priced out the same size system for her house.
That means the geothermal system would cost $15,200 more and that would take 8+ years to pay off at today's rates. If I financed that at 8% for 30 years it would be $110 a month or $1320.00 a year. If I could get low cost financing, like 5%, then my yearly cost would be $996 for a really good positive net effect.
It's important to note that is just the dry numbers. Reducing my carbon output 50% is a big deal as is spending less money on utility bills and spending more money on my home. In the future, the reduced electricity use would make a PV system much smaller and cheaper.
Bottom Line - This concept's time has come but we need a little maturity in the market to get prices down and make this a no-brainer. Right now its a good deal if you have the money or the equity in your home to borrow against. We all agree that energy prices will also go up, and then the deal would get even sweeter.
I hope my old system breaks down again soon...(what am I saying?)