I recently had a geothermal heat pump installed that uses the DX method for heat exchange, and I'd be happy to share some of my experience.
Our 2500 sq. ft. two-story house was built in the 1880s, but has some blown insulation in the walls and new vinyl windows. There are still air leaks here and there that I can improve on, but if you're building new, you're already way ahead of me as far as the tightness of your building. I was a little hesitant to go with a geothermal system simply because of the age of the house, but I got past that and will keep working on tracking down any leaks. Our previous unit was a 15 year old propane furnace and standard A/C unit. Propane costs have increased from about 69 cents a gallon (in the summer, at least...I remember paying 49 cents for one delivery) to over $2.50 a gallon in the winter, although I'm capped at $2.09 this heating season, so that's one of the major reasons we looked at geothermal.
Now, to the system itself. The heat pump is an Advanced Geothermal unit with the separate desuper water heater that is plumbed into my propane water heater. It is a 5-ton unit with ten 70-foot-deep ground loops. It took the contractor three days to do the drilling (mostly a one-man operation), and the field is about 20 feet from the house. The inside work took about four additional days with a crew of three. The contractor I went with has a lot of experience with this type of system. In fact, they have enough business to keep four drilling rigs running almost year round. I had my system installed in January, and that was after signing the contract in October, so I had to wait in line for a while. I had some friends and family suggest other contractors (mostly for water-based systems), but I was really sold on this contractor's experience and the number of units they have installed in our area. I mention this because I would really be wary of anyone who has only installed a few systems. Look for someone who does a significant amount of geothermal business.
My system is backed up with a high efficiency propane furnace, and the duct work was reworked to improve the system balance. The previous system was a quick and dirty install because that was all we could afford at the time, with only one central cold air return. The contractor added four additional returns and connected to some old duct that runs up to the second floor which had been inactive, so at least we now have a little heating and cooling upstairs. They also had a subcontractor come in and spray foam insulation on the outside walls of the cellar and crawlspaces to help cut down on air intrusion. The total cost of the drilling, the copper lines, the heat pump, backup furnace, spray foam, the duct improvements, and labor was just under 25K.
Out of that amount, we will get back almost $7500 in tax credits, plus our utility company threw in a $600 rebate for retiring our old system. They also reduced our electric rate for installing the geothermal heat pump, which was a bonus we weren't even aware of when we decided to go with the geothermal system. In addition, our State provides reduced rate loans for energy efficient improvements, so we were able to take out a loan at 2% rather than drain a significant portion of our savings account. If you haven't done so already, I would encourage you to see what incentives are available in your area. Almost everyone knows about the 30% federal tax credit, but there is other help available as well.
The system has been running for a couple of months, so I don't have a complete picture of the operating costs vs. our old system, but the initial data is encouraging. For March, which has been colder than average for our area (in fact it's snowing right now), the heating cost was $110.00 (the contractor installed a separate electric meter just for the geothermal system so we can get a pretty accurate idea of operating costs). I expect it will be quite a bit higher for the December to February time period, but there will be months in the spring and fall where the system should hardly run at all. I don't yet have any data for cooling in the hottest summer months, but I do know that our old A/C system would add about $100 a month to our electric bill in July and August. That $110 for March would have bought us about 50 gallons of propane, and I know from past experience that we could easily burn that much or more in a week during the winter. Additionally, our house is now much more comfortable. We used to keep the thermostat set at 63 during the day and 55 at night, and now it is set at 68 most of the time. We still have to turn it down at night sometimes, because even at 68 it gets too warm upstairs for comfortable sleeping, despite the minimal duct work to the second floor. The overall system noise has also been reduced, and we no longer have an ugly A/C unit sitting outside our kitchen window making noise. Also, since the day the heat pump was fired up, the backup furnace has not had to kick in, so with our only propane use being the stove and water heater, the gauge on the tank has barely moved. Taking all of this into consideration, I'm very glad we went with geothermal and would do it again in a heartbeat. It's a little early to tell, but unless propane prices suddenly go back down to less than a buck, I think we'll recover the system cost with savings in about 8 to 10 years.
Best of luck with your new house! |