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Geothermal heat pump vs air source heat pump vs gas

jessica13
13 years ago

Anybody have experience with Geothermal heat pumps, air source heat pumps?

Geothermal will cost an additional $40,000 ( or $25,00 after 30% tax credit) and air source heat pump with variable gas furnace will be an additional 5,000 (no tax credit). Our new house we are building is in Wisconsin and we have natural gas available.

Are either of those options worth the extra cost compared to natural gas?

Comments (27)

  • booboo60
    13 years ago
    last modified: 7 years ago

    Just my opinion and experience; if you are going to build your "forever" home and have the resources to do the geothermal I would choose it. I think it is the most efficient but to get your "cost back" it will be many years down the road. If this is in a sub division and you will only be there 4 or 5 years I would do the natural gas.
    Good Luck!

  • athensmomof3
    13 years ago
    last modified: 7 years ago

    I will be interested to see what folks say. Our architect also recommended the geothermal. I guess it will also depend whether we have the extra 25k when it comes down to it :)

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  • gopintos
    13 years ago
    last modified: 7 years ago

    We are in Mid Missouri and we went Geothermal with an open loop pump & dump.

    I think there are like 4 or so options. Closed loop using geo wells vertically, horizontal closed loop by burying your lines underground, or closed pond loop, or the open loop which we are using and we are dumping into the pond. Most of the geo guys that I received quotes and information from, thought this was the most energy efficient for our particular situation.

    I also received a lot of helpful information from the utility company.

    I could be wrong on any or all but that is the way I understand it.

  • 2ajsmama
    13 years ago
    last modified: 7 years ago

    Check into rebates from your state or power company. We built too early for Fed rebates/credits, but got $2000 from electric company. We have a 4 ton vertical closed loop system with an 80 gallon holding tank for hot water and another 80 gallon wired hot water heater to bring whatever the buffered water is up to 120. I haven't tried turning off the power to the 2nd tank in summer but believe that it comes up to at least 100 F just taking heat out of our house (2700 sf, we keep temp at 74 in summer, 66-68 in winter).

    We would have done horizontal ("Slinky") loops instead of drilling but too much ledge. We also had hard time finding water so would have had to drill at least 2 wells to find water, we ended up with 2 geo wells and 1 water well.

    When we priced out oil-fired "Hydro-Air" plus central AC in 2007, we found that the GSHP system would only cost us $6000 more (and that included $9K for the two extra wells, trenching wasn't that much extra since we brought it to house in same trench as water, wells have to be 25ft apart but lines can be next to each other). I'm not sure why you say it would be $40K "extra" for you since our entire system cost $36K. We figure with oil prices the past 3 years (moved in Labor Day 2007 so this is 3rd winter) we've already made up that $6000 (or will by end of our 3rd full year anyway).

    Depending on what your electric rate is, your Aux Heat could either be electric resistive "strips" built into the heat pump as ours is, or natural gas if that's more cost effective (we don't have gas in our neighborhood).

    Geo will be a selling point and raise the value of the house (though here in CT town isn't allowed to assess property taxes on the equipment, so our tax card lists it as "Electric" heat and no AC). I think if you're staying long enough to make it worth building at all (vs buying existing) that it's worth putting the GSHP in. Check into the cost again though, that seems high. And look for "energy efficiency" loan (possibly through state or electric/gas company) or mortgage to pay the additional cost.

  • creek_side
    13 years ago
    last modified: 7 years ago

    We looked at geothermal versus air source and found no payback, even with the tax credit. Your situation may be completely different, though.

    Do make sure the people that are quoting the systems are highly experienced. A lot can go wrong with a geothermal system that can be very expensive to rectify. Not so much with an air source system.

    Be especially careful to check out the warranties. The last information I had showed Waterfurnace giving a 10 year parts and labor warranty, while Florida Heat Pump gave only a one year parts only warranty.

    Do make sure the bids spec cupronickel heat exchangers, which are highly corrosion resistant. They are usually options.

    Make sure whoever is bidding does a full Manual J heat gain/loss analysis. Ask them for the numbers. If they size the unit strictly by the square footage of the house, don't even consider them.

  • robin0919
    13 years ago
    last modified: 7 years ago

    It shouldn't cost anywhere near that much extra!!! Get more quotes!! Ck out greenbuildingtalk.com. They have a forum dedicated to Geo. After rebates, the cost comp. to an air heat pump would be around the same or even less. Alot of folks in the business are trying to rip folks off because it is new and greener!!

  • ramor
    13 years ago
    last modified: 7 years ago

    It cost us an extra $40K but the tax credit is for the cost of the entire system less the ductwork so the credit is for more than 30 percent of $40K. Our payback even after the tax credit will take about seven years at current rates. Our system is 12 tons with ten vertical wells.

  • srercrcr
    13 years ago
    last modified: 7 years ago

    My rule is if you have available gas, go with regular A/C with a gas furnace...it is your cheapest alternative. If you'd rather have an all electric home, go air source heat pump with heat strips for very cold conditions, then it's regular A/C with heat strip electric furnace. Don't buy something you don't understand.

  • macv
    13 years ago
    last modified: 7 years ago

    "Don't buy something you don't understand."

    That would eliminate the last 50 years of advancements in building technology.

  • doctj
    13 years ago
    last modified: 7 years ago

    In our case with tax credits state and federal, Geothermal cost less than a conventional system so immediate payback. Try and get a local installer with a good warranty.

  • ponydoc
    13 years ago
    last modified: 7 years ago

    We opted for geothermal - I think the "extra" cost for our 3400 sq ft home was about 10Kto 12K. I would get a few more estimates.

    As far as "not buying something you don't understand" - Fortunately my clients don't feel that way!

  • creek_side
    13 years ago
    last modified: 7 years ago

    David's post reminded me that the geothermal tax credit nolw requires that the GSHP also supply domestic hot water. It's done with a desuperheater, which is an option with some makes. Make sure it is included in the quote.

  • 2ajsmama
    13 years ago
    last modified: 7 years ago

    I think your climate might be colder than ours (CT), another reason not to go with air source. Ground temp is more stable (and warmer in your cold climate) than air.

    We have 2656 sf 2 story home R-22 insulation in walls, R-19 in basement, R-38 in attic. Andersen 400 series windows - sorry I never got the Manual J calcs otherwise I'd share them with you. GSHP is 4 ton Climatemaster Tranquility 27 with desuperheater, two 80 gal stone-lined Vaughn water tanks (one wired, one connected to desuperheater). Cost from geo contractor was $24,773 plus $600 for humidifer add-on, $1950 for two zones (which we shouldn't have bothered with, but we had the wiring in place from modular company so we did it - and now we *do* keep upstairs and downstairs at different temps). Then $450 to electrician to wire 220V running from main panel on one side of basement to subpanel on other side (incl 2 breakers for heat pump, one for hot water heater, and an outlet near subpanel for HVAC use). Chases were already in place, as was low-voltage wiring for thermostats, but HVAC contractor ran ductwork for 2 zones. Two 279-ft wells, incl. loops and grouting, etc. Purge and testing done by HVAC contractor (incl. in $25K). So total was $36,773. After $2K rebate from CL&P it was $34,773 and I think we got $500 rebate from IRS so down to $34,273 (of course Obama is offering a lot more now). A second rough quote (based on house plans) for 4-ton Envision system with a single Vaughn tank was $35,750, 1 zone with no wiring (so add $450 for electrician) or permit fees (not sure what those ran, were included in quote we took).

    A friend of my husband works with an engineer at a nuclear power plant here who installed geo in his home, not sure what year, (2004 or 2005) he has 2900sf modular. Here's what he told us "I spent about 31K total which included the wells at ~8K, the heating and cooling unit (including hot water option) and the duct installation at ~18.5, and the hot water tank and related materials. The unit I bought was either 5 or 6 tonne and is made by Hydro Delta."

    We asked our HVAC contractor who installed the GSHP for quotes on oil-fired options when it looked like trenching through ledge would be a problem (until I found we could bring it to the house in same trench as water). One quote for an oil-fired Lennox "Elite series" furnace, 330-gal oil tank and a 3-ton Lennox 13.5 SEER CAC (no hot water, no wiring) was $22K. The other for Lennox "Signature series" furnace and 20 SEER CAC was $25K.

    I can't find the quote for HydroAir but I recall it being around $6K less than what we ended up paying for geo.

    I know these prices are from different area of the country and 2.5-4 years old, but HTH.

    Our base electricity use (lights, hot water, appliances incl dryer) runs 35-36kWH/day during the non-cooling, non-heating seasons. Summer isn't much more (hit 41.65 kWH/day last August while running dehumidifier, June was cold and wet so no AC running, July was hot but not humid, ran AC but usage only went up from 34.93 kWh/day in June to 36.33 kWh/day in July, summer 2008 was more like 40 kWh/day).

    The electricity use spikes in the winter - but we found the breaker labeled "Air Handler" was actually a 10kW heat strip that we had been leaving on all year, turned the other 5kW strip on each Tgiving through March. This year we had both breakers off until a cold snap a couple of weeks ago, have been running the 10kW strip this billing cycle but sorry no data yet. I can update next month.

    Feb 2008 we hit a high of 76.63 kWh/day usage (so roughly 40kWh/day more than baseline), at 18 cents/kWh that means we spent $7/day to heat the house to 68 when it was supposedly 27.8 average outside (but I'd say about half the 30 days were a good 10 degrees below that as *highs* and the lows were in single digits).

    Last billing cycle we were running all geo (no heat strips/breakers on), used 49.69kWh/day when average was 40.4 outside, but we were on vacation for a week and had the heat turned down to 55, hot water heater off.

    Depending on your electricity rates vs natural gas, you may want to look into natural gas vs resistive heat as your Aux Heat, in that case if you have to pay for the furnace anyway and rates are low then there might be a really long payback for geo and it might not be worth it, but check into the true "extra cost" for geo first. I wouldn't recommend air-to-air heat exchanger in your climate.

  • 2ajsmama
    13 years ago
    last modified: 7 years ago

    Oh, BTW, just roughly figuring oil at $3/gallon, we used 1000 gallons/yr in our old house (same size but not as well insulated), we figured we'd be spending $3K/yr on oil. Now, that's really rough (and our old house used oil boiler for hot water too, no tank), but we were also spending about $100-150/mo on electricity there too, and the rate was about half of what it is here in CT, we know people with same size houses that spend $200-250 on electricity (no heat, some have hot water) here in CT. So we roughly figured on spending $3K/yr on oil and $2400 on electricity. In 2007 my cousin (new house, a little larger but not much, not far from here) spent $9K on oil!

    We've spent a total of $4200 on electricity for the past 15 months (sorry, don't have online data earlier than July 2008, I'd have to try to pull old paper copies). Let's say $200/month is base electric (36 kWh/day), that's $3K so we've only paid an additional $80/mo to heat/cool this house (mostly heat, electricity bill can double to $400 or over in Feb).

    Compare that to easily 200 gallons/month each winter (x 4 months) to heat (another 200 gallons used to last us all summer for hot water in old house), at $2.50 - $3/gallon that's $500 - $600/mo (again x4) to heat, and who knows what conventional AC would cost us in the summer?

    I know it's not apples to apples since I am looking at oil prices and I have no idea of your house size, load, or utility rates, but I figure that since we've probably spent $8400 on electricity in past 30 months we've been in this house, $6000 of which is non-heating/cooling, we've spent only $2400 for heating through two entire winters, that's almost what we would have spent in one winter with oil (800 gallons at $3/gal). Plus we figured who knows what oil (or any fossil fuel) prices will be in the future.

    So maybe we haven't seen our ROI yet, but I think we're going to be close by the end of this winter, or certainly by this time next year. Again, this is not taking into consideration what AC would have cost us in the summer with CT's high electricity rates.

    If we can figure out a way to get a wood stove in this house (builder didn't leave room for chimney - upstairs window in the way) as originally planned our heating bill will drop.

  • ramor
    13 years ago
    last modified: 7 years ago

    My extra cost after tax credit is only about $15000. Not having the outdoor condensing units for the ac is almost worth this amount to me. Most of the time I would be able hear them if I were in my back yard. It is really quiet most of the time where we are building and I really enjoy that. Also, you need to build a fence around them which helps with the noise and hides them, but is also an additional expense.

  • jessica13
    Original Author
    13 years ago
    last modified: 7 years ago

    Thanks for the info. I have gotten 2 bids so far. One is from the builder's contractor who is recommending two 6 tons climate master heat pumps with horizontal piping for $60,000. The 2nd and more experienced contractor has quoted a 5 ton and a 4 ton Envision with horizontal piping for $50,000. I am waiting for the 3rd bid and then will post more info.
    Our house is 6500 sq finished space incl 1st, 2nd flr and basement.

  • 2ajsmama
    13 years ago
    last modified: 7 years ago

    Wow, 12 tons??!! ramor looks like most comparable (though I don't know climate).

    We were planning horizontal trenching since my dad could do the excavation (he and my uncle did our foundation and septic). But too much ledge, and contractors quoting to me said vertical wells are more efficient in our climate. You might want to get quotes for vertical as well as horizontal.

    The $50-60K is total, right? So figure something like $40K after credits. How much would a natural gas furnace for that large a house cost? Will 12 tons supply 100% of your heat in the winter or will you need Aux Heat? These are things you need to figure out before you can calculate ROI/payback.

    I was just saying to DH I'm glad to be paying $3000/yr for electricity including heat and not $3000 for oil and then have our electricity on top of that (probably another $2K+).

    Good luck in making your decision and Merry Christmas!

  • 2ajsmama
    13 years ago
    last modified: 7 years ago

    DH just told me they added this to their website. I'd take it with a grain of salt, as we are not spending near what they figure (put in your location and some info about your house, but not a lot of detail). They figure with "Good" insulation and sealing in a new house, we'd be spending $4217/yr on electricity with a GSHP (no info on what size HP they assume). With "Excellent" insulation we'd still be spending $3950/yr. "Appliances and Lighting" categories add up to about what we figured ($170/mo), hot water and heating/cooling add up to $159/mo. CL&P has set our "budget payment" this year at $324/mo so that's close, but I figured it should be closer to $300/month based on last year's usage (and we changed suppliers so saving 2 cents/kWH now). We'll see how close we are at the end of the summer - they might owe *us* money. Then again, it's been highs in the teens lately and I've been running the oven every day making cookies etc. so this month's usage will be higher than normal.

    Here is a link that might be useful: Climatemaster savings calculator

  • sniffdog
    13 years ago
    last modified: 7 years ago

    Air source heat pumps don't make sense in areas where winter temps frequently fall below 32 degrees. Once you get below freezing, you will be running the auxillary heat a lot. If you decide to go the air source route, you will want a second stage gas fired auxillary heat.

    I live in the mid-atlantic region in the mountains and selected GT. That choice was coupled with a blown cellulose insulation package. My other choice was a propane heat/electric AC with a foam insulation package. Both options were roughly the same install cost. Both would have provided similar energy efficiency.

    At the time we selected, propane was 3.75 a gallon and rising (with no end in sight) so we went with GT.

    The delta cost for the GT system (above the cost for a HE propane heat and electric AC system) was $15,000 for the heat pumps and loop plumbing (including pumps) plus $17,000 for digging the pit. The pit excavation should not have cost as much as it did but it is a 12 ton system and the hole was gigantic (120' x 48' x 6'). We live on a mountain and hit a bunch of boulders that required special equipment to get out. Rocky soil also required a 1' base of stone dust to cover the loop piping.

    The total cost for the GT HVAC system including all ducting was $50,000 plus the pit excavation cost of 17K.

    It is a large investment and I would only recommend it if you plan to live in the house a very long time. My heating bills are great - maybe 300 dollars maximum a month during peak winter for an 8500 square foot home (5900 living and the rest a condiitoned but unfinished basement).

    Make sure that whatever equipment you choose can be maintained by more than 1 very qualified HVAC company who has many years of GT experience. In my area there is only 1 GT company who has over 20 years of experience but I am stuck with them for maintenance. There have been times when I wanted to fire them but cannot. Local competition is a good thing.

    Also - if you build a tight home make sure that you consider ventilation and dehumidification in the HVAC design. I wound up adding both a whole house dehumidifier and energy recovery vent after we moved in becuase we had basement moisture issues as well as stale air in the winter. Tight homes are great for energy efficiency but can create health issues too. It is easy to deal with as long as you plan for it.

    Good luck with the build.

  • creek_side
    13 years ago
    last modified: 7 years ago

    Air source heat pumps don't make sense in areas where winter temps frequently fall below 32 degrees. Once you get below freezing, you will be running the auxillary heat a lot.

    I respectfully disagree. The balance point for our current air source heat pumps is well below freezing. This morning it was 25 degree outside and our three year old low end heat pump was keeping up just fine without using the aux heat. It will provide usable heat (COP > 1) almost down to zero, although from about 15 on down it needs the assistance of the heat strips to keep the house at temperature.

    From what we can tell so far, the two stage high end air source system in our new house will be able to keep up without help all the way down to zero. Modern air source heat pumps are very efficient.

  • vhehn
    13 years ago
    last modified: 7 years ago

    "Air source heat pumps don't make sense in areas where winter temps frequently fall below 32 degrees. Once you get below freezing, you will be running the auxillary heat a lot."
    not true at all. it is 16 degrees here right now and my heat pump is keeping up without the aux kicking on.
    in my opinion is just silly to spend 60k on an hvac system for a single family home.

  • srercrcr
    13 years ago
    last modified: 7 years ago

    sniffdog: I'd be curious how your $300/mo cost stacks up to what Climate Master claims in their Savings Calculator.
    One big discrepancy I got was they say my hot water costs me $570/yr with propane, but I know it costs me around $100/yr. Anyway their calculator gave me a $475 savings per year with GT, but with the aforementioned discrepancy, I'd say there is no savings at all.

    Here is a link that might be useful: Climate Master Savings Calculator

  • 2ajsmama
    13 years ago
    last modified: 7 years ago

    I think you were referring to me, not sniffdog (if he has $300/mo bills with that big a house the rates must be a lot cheaper than CT!).

    Anyway, Climatemaster figured rates at 17 cents/kWh (we were paying 18.5 but just dropped to 16.5 so I left it). They figured $170/mo for appliances and lighting (figures roughly to the 36 kWh/day we *do* use on non-heating/cooling months, with our rates it's more like $180 even with the 2 cent reduction - was closer to $200) and $159/mo for heating/cooling. That adds up to $329, our monthly "budget" (stays same year round, adjusts once a year) payment is $324 but as I said I think that was set high since last year we were paying $274/mo and we owed at the end of August.

    Since we switched suppliers (for 2 cents savings) a little late in the year and I've been baking all of December, this year's bills might be a little skewed to the high side, but I'll report Jan - Aug totals next summer (not that that helps the OP much). Of course the 2 cent reduction in our generation rate will offset the higher usage, so let's just say that Climatemaster figured that we used 1000 kWh/mo (at 17 cents) for appliances, we figure more like 1080 based on actual usage but that *includes* hot water which I have no way of breaking out separately since I don't turn off the water heater in the summer (though I could just to see what the desuperheater gets it up to). That leaves 935 kWh/mo (averaged) for heating/cooling *and hot water* (which is a big thing since I run about 7 loads a week).

    We just had settings adjusted this summer for frost control and for "dead band" between heating and cooling of 5 degrees, plus we've made sure *both* breakers for Aux Heat are off during the fall, so this should be more efficient. Unfortunately we found that we can't set a lockout temp when we have more than 1 zone, so we've got to "manually" control that by turning breakers on when we figure it's getting cold enough that we will need Aux Heat. This is a Honeywell IAQ thermostat - other thermostats may not have this quirk.

  • sniffdog
    13 years ago
    last modified: 7 years ago

    Our rates in VA are 11 cents per kwh (peak winter & summaer rate) with all taxes and fees included. non-peak loaded rates drop to 9 cents per kwh.

    My HVAC portion of the electric bill was 300 for the month of Jan 09 which was the coldest we had seen in a decade. The actual electric bill for that month was 425 which covers all electric items - and we know from past monitoring that we use 125 per month for non hvac related items during the winter. My total electric bill for the entire year was 3500 dollars.

    It will take about 10 years to break even on the added expense for the GT. We plan to be in the house for 20 years so the investment made sense for us.

  • jimandanne_mi
    13 years ago
    last modified: 7 years ago

    jessica, from the information you've given in the other threads about your builder, I would definitely NOT use his sub since there are other alternatives!

    As creekside said, be sure the person bidding the geothermal does a Manual J to get the correct size for everything--VERY IMPORTANT!!!

    Our most experienced local geo guy used Water Furnace in our home. They did 4 horizontal bores for the loops--more expensive, but was our best workable option. Too early for tax incentives. ;o( We probably won't live long enough to get our money back, but we LOVE the comfortable heating and cooling.

    We also did solar hot water, which is cost effective to do now. We have 3 water tanks. DH figured out how to hook everything up so whichever tank is hottest--the geothermal hot water or the solar hot water--provides the water at any given moment. He ran his ideas by the geo guy and the solar guy to be sure everything would work together. His other idea that he hasn't pursued yet, is to get the excess heat from the solar hot water to be used by the geo system.

    Anne

  • Ron Natalie
    4 years ago

    I have four geothermal heat pumps. Two are water-air units that provide rapid heat and airconditioning. Two are water-to-water units that provide the heat for the radiant floor loops (this is a 7700 sf house and one of the water units also provides heat for 3000' of airplane hangar).

    All the units are WaterFurnace Envisions. WaterFurnace at times is a bit balky to deal with and the local contractor is somewhat inept but even with all that, we've had pretty good experience with them. They do what they're supposed to.

    I've got 7 wells that provide the groundsource. There's no "backup" system like you would have with resistance strips or whatever in an air-air heat pump (the ground doesn't ever get too cold like the air does).

    One of my water-air units even provides preheat for the domestic hot water when it is running in air conditioning mode (no need to waste that heat). There's a small exchanger (well, in fact, it's a small electric water heater that's never turned on) that fronts the Rinnai.

    As far as operation goes, other than the two circulating pumps going out to the wells, there's not anything much different between these heat pumps and any other. They're pretty simple inside. I had a pump go out in ten years of operation, but that's a minor repair. I'm thinking about keeping a spare around (my wife and I already tag-teamed a replacement of a hydronic loop pump when one of those died).