Geothermal & 5 lb Heat Pump

Hi sense community!

I’m rocking a 19 year old gas heater and I have a +25 year old A/C unit as well. I had a HVAC guy come out yesterday to quote me replacements for both of those (About $8,500 to replace both together with a little duct work repair). He also quoted me to install a geothermal unit as well ($20,500).

My question to the sense community is this, how much is your monthly and yearly Kwh usage with geothermal? What does a typical Summer month look like to you compared to usage during a Winter? Of course I’m asking this knowing that different sized homes are going to have different results and of course house location will matter too, but I’d like to go in knowing the general increase in electricity usage that I’d have.

Thanks for any data you can provide.

Ouch $25K for geothermal! Your HVAC guy should be able to provide you with that information. If he can’t; get yourself another quote. You need to take a hard look at your “return of investment”, and then decide.

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I would say, what you can expect depends on your house, location, and thermostat settings. It’s a little complicated trying to predict costs (or savings) but you could start by adding up your gas and electrical usage for heating and A/C and converting that to BTU’s. According to the Department of Energy, geothermal systems cut you energy bill by 65% (again this is a fuzzy number since your “energy bill” depends on what you pay for electricity and gas, etc). Then take your total BTUs and multiply by .35 to give you the expected BTU usage with geothermal. Divide that number by 3412 (BTUs/KWH) to give you the expected annual KWHs with the geothermal system, then multiply by you cost per KWH to provide the annual cost.

This would provide a very rough estimate.

I am an advocate of geothermal. My experience is that it provides a much higher efficiency than expected by the government. I live in Maine so my greatest energy usage is for heating, but that is where geothermal really shines. Water comes out of the ground year around at between 50 and 60 degrees. In the winter that gets “heat pumped” up to about 100 degrees for the radiant floor heating loops. In the summer, the water temp gets pumped down to about 45 degrees for the A/C air handling coils. We also get most of our domestic water heating from the system. The summer A/C is very low cost compared to an air to air system. Our 5 ton system used about 9400 KWH in 2019 which cost us about $1600. This is based on Sense data from last year monitoring the heat pump, the well pump, the air handler, and the various water circulation pumps. The system was installed 9 years ago and after some initial setup issues, it just hums along. It paid for itself in 6 years. Your experience may vary.

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Thank you rflint for going out of your way to provide that info!

If I can use up a little more of your time, I wanted to clarify your formula really quick

My BTU: 186,660
Multiply by .35: 65,310
Divide by 3412: 19.14 kWh (Did you mean daily kWh usage? That number is too low for annual right?)
If it is daily then 19.14 kWh * 365 = 6,987 (annual kWh)
6,987 x .19¢ = $1,327.45 (annual cost)

If I’m using your formula correctly, I think I may be in a bad position for geothermal…

If I put in a new heater and A/C, I was quoted $8,000. Geothermal will run me $13,000 after the federal rebate.

Right now I spend about $1,300 on gas to heat the house yearly, and $500 for A/C = $1,800 annual. While geothermal is certainly cheaper to use, its only saving me about $473 a year, which means it would take up to 11 years before I see my initial investment returned. Am I crunching the numbers correctly?

Again, thank you for your time

Please give me what you used for electricity for AC and gas last year. Electricity in KWH and gas in what ever form it comes in (pounds of propane, cubic feet of natural gas etc). Also what your unit price for gas. Then I can better answer.

Total Annual kWh: 11,201
Total A/C: 606 kWh (I only ran A/C in July because it died around the 1st of August, but I suppose a normal family would run it June-August, so 606kWh x3 = 1,818 kWh hypothetically if I did use A/C all summer?)
Total Propane: 1,053.43 Gallons @ 1.33 a gallon = $1401.06
Last year in 2019, I was paying .16 per kWh, though this year they are raising it to .19

Sense still hasn’t identified my HVAC fans or my furnace, so I sadly can’t see those numbers.

Thanks rflint, I really do appreciate it.

OK Benyoung777
Your propane BTUs are 1,053 gallons X 91,333 BTUs/gallon = 96,173,649 BTUs used

Your electricity BTUs = 1818 KWH x 3412 BTUs/KWH = 6,203,016 BTUs used

Total of 102,376,665 BTUs (Which would cost 102,376,665 / 3412 X .19 = $5700 if you were using electric heat and 100% efficiency AC)

So if we assume your heat pump will provide the heat/AC for just 35% of the cost it would be 0.35 X $5700 = $1995 per year, more than your current costs.

You may be correct that a geothermal heat pump would not pay for itself in your case. Your cost of propane is very good. You are paying $1.33 / 91333 = 1.456 times ten to negative five per BTU for propane and .19 / 3412 = 5.568 times ten to negative five for electricity. Clearly electricity is much more expensive be BTU for you and can’t offset the high efficiency of the geothermal system.

You might talk to your salesman and see what he has to say about cost comparisons.

Hope this helps.


Thank you rflint! Yeah I have no idea why propane prices are so cheap in Iowa. Last year it was even less at 1.19 per gallon. Its not something I can complain about as far as my bills go, however it doesn’t help the geothermal argument haha.

However If I were to get geothermal, it wouldn’t be for any money savings— I’d have to be doing it to be a better human and to do my part to reduce my carbon footprint. Another thing to consider is will propane prices always be so low in my area? But regardless, thank you for your time helping me crunch the numbers!

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Good for you for considering the carbon footprint issues. It also helps if it makes economic sense to convert. As I understand it, your heating and cooling systems are up for replacement so you have to spend something just to keep warm/cool. It’s like building your first house, you aren’t investing for payback, you need a place to live. So the question comes down to what you can afford now and are you looking for short or long term costs of operation.

I used a very conservative .35 percent number from the governments website (it assumes a system makes 2.85 BTUs of heat for every 1 BTU of electric energy put in) but can tell you that my system runs very close to .20 percent (it makes 5 BTUs of heat for every 1 BTU of electricity put in, or 500% efficiency). That is measured performance using full instrumentation of the system, not theoretical or sales brochure numbers. When first installed in 2011, we were paying $3.23 per gallon propane and $0.14 per KWH for electricity. It payed for itself in six years (with the government tax credit taken into account). Anything that pays for itself in 10 years or less is a good investment in my mind since it is providing about 6% or better annual return. Our system uses radiant floor heating, pex tubing installed in a concrete slab in the basement and first floor (with tile). That allows us to run the system very efficiently. During the heating season, we only pump the water temperature in our holding tank up to 95 degree. This water is then circulated through the floor. Radiant floor heating is very nice on a cold winter day, you can walk around in your bare feet on a tile floor. However, if you don’t have radiant heating, you will need to pump the temperature up to a higher level. An air coil (in a ducted forced air system) would work much better at 120 degrees or higher, same for baseboard heating. The higher you need to pump up the temp, the lower the efficiency of the system (think of rolling a rock up hill, the high you need to go, the more energy you need to put into it) That is why I suggested you talk to your system salesman. Some are just selling stuff and some are able to give you a detailed estimate and options to improve performance. Geothermal was new and somewhat controversial before we installed our system so I spoke with the engineer in NH who pioneered the concept and he gave me some info that showed me how to optimize.

There are now other options to geothermal however that might be more attractive. Maine is the oldest state in the nation, per capita wise, and most people have a very short time perspective (they can’t see investing for the next 10 years because they likely won’t be here that long, I’m in my very late 60’s so but still think a ten year payback is worth going after because I’m planning to live to 100!). Split mini system heat pumps are very big now in Maine if you can believe it. I had one installed in a small guest house last fall and it provided heat all winter, even down to -15 degrees at less cost than we had been paying for oil and electricity. They are a much lower upfront capital investment, especially since you don’t need the geothermal well or ground loops. They are very efficient and provide both heating and cooling in one system.

Finally, if you are paying $.19 for electricity, you should very seriously look at some solar panels. It will depend on your state’s utility regulations but with net metering, solar panels in Maine (not known for being very sunny) can pay for themselves in 10 years or less. I have a 19.6KW solar system that I installed in three phases to cut down on the initial investment (paid for the system outright versus financing) and we now have no electric bills (except the monthly connection charge of $12 for the rest of my natural life and likely the same for my son when he gets the house). Our house is all electric. All we need to buy now is beer and tacos, healthcare, and college for the grandkids.

Finally, whatever decision you make takes some research on systems, State and Federal regulatory and tax issues, a little prognostication on future energy costs, what is cheaper for you versus better for the nation and the world, and faith in your decision making.

What ever you decide, take care and good luck.

From the great state of Maine to the great state of Iowa




Nicely argued. I would also hope that in the calculus, even if you don’t live to 100, that the primary factor is the longevity of the house and the energy tech therein. Geothermal is interesting in that regard because in theory the buried pipes will outlive the heat pumps and above-ground gear … and would still be usable even if a new house goes on the site.

You make me consider: Solar house vs geothermal house burning down.