Trying to justify geo cost, looking at all factors
I'm thinking about installing geothermal at my house. I've been using this spreadsheet to look at costs of different fuels:
My current system is forced air propane and I pay $3 a gallon for propane and 12 cents for electric. So propane shows about $35.58 per million btu and geo @ COP of 4.6 shows $7.90 per million btu. So geothermal would be 4.5 times cheaper. My question is, this spreadsheet doesn't take into account the electricity use of the furnace fan (single speed fan, %92 efficient furnace.) I'm thinking that fan costs me $10 a month to run. So do you factor that in? I mean, that's only probably $50 a year but it's a small factor to consider?
What do you guys think about that spreadsheet from EIA? I know I use at least 700 gallons of propane, so that's about 64 million btus so I should see about $1800 savings per year in heat costs alone, not even including the hot water and a/c savings. Is my logic correct? Is there something I'm missing and maybe I can't rely on that spreadsheet? I have some contractors doing heat/loss calcs , giving me estimates this week.
2400 sq foot home, tight, Allentown, PA.
Wow! $3 per gallon! We are at $1.90.
It looks like you are close on your figures. You need to change the AFUE to 90 to get an accurate figure for your furnace. I do believe a blower motor is figured into the COP. Usually you will get a package unit and remove your LP furnace completely.
When you say your home is "tight" what do you mean? What kind of leakage rate when tested with a blower door?
Worry is a really gross misuse of one's imagination. -- PHM
Oh, how I would love $1.90 propane. I don't understand how it can be that much cheaper in WI than PA. Well, you can see why I want to go geothermal.
You say change to %90 on propane just because %92 isn't really %92? That %92 is only in ideal situations and I'm really only getting %90? But the cop on a geo heat pump of 4.6 really is 4.6? I changed the spreadsheet to %90 for propane and that causes propane to show $50 more per year, just by adjusting by %2. So now I'm over $1800 a year savings.
I meant the fan on the furnace, not the geothermal heat pump. I'm just wondering how much a fan on a propane furnace really costs per month. I know my electric bill seems to drop by $20 in the mild months like June when there's no a/c or heat, so I guess that's a good way to tell how much the fan is costing me. So I can include that amount on my savings. With a geo heat pump, during some cooler months like November, I may not see my electric bill even rise because the geo heat pump will use less electric than my furnace fan did, perhaps?
By tight I mean 2x6 walls so r-19. Probably not really tight, just not really leaky like an old house. House is 9 years old.
Here's results from blower door:
Measured leakage area 1.41 sq feet.
Test data: 50 pa house pressure, 120 pa flow pressure, 1714 cfm.
Avg air change rate: 7.83 per day.
Manual j air change rate: c=135 n=.65 winter = .041 per hour or 128 CFM, summer = .24 per hour or 77cfm.
Constant mechanical whole building ventilation rate = 61cfm.
How many sq feet is the home? Last November we changed out a propane furnace and 10 year old AC for a geo system(5 ton water furnace dual capacity) and the customer has saved about $3,800 a year, but they were also using 1,600 gallons per year. You should have NO problem justifying the geothermal in longevity, added comfort, reduced noise levels, increased home value and of course doing something green. I don't know if your part of the country does vertical or horizontal loops but if they do horizontal check out my YouTube listed below to see some propane to geo change outs and how to put in a ground loop. The most important factor is to find a contractor that knows what they are doing. I have seen 20 years of experience mess up jobs and newer companies get it right so really compare and contrast your dealers and ensure they know their systems. Look for IGSHPA certified installers and as a WaterFurnace dealer I would check their dealer locator. I have represented other brands before and I can tell you that nobody trains and supports their dealer like WaterFurnace.
Home is 2350 sq ft. Seems like every contractor so far said they do vertical. Yep, I had a waterfurnace guy here this evening. I'll check out your youtube, thanks. I have an acre lot but every contractor is telling me I don't have enough room for horizontal and vertical is better, but I don't see why they couldn't put in a loop, I have wide open back yard. I have one more guy coming Saturday, his business is all geothermal, will see what he says.
I'm really hoping to get away with 3 tons based on the blower door test and heat/loss calc.
I had one guy tell me 4 tons already, but he also tried to pull a fast one and entered 9 cents/kwh when I know that he knows it's 12.5 cents and hasn't been 9 cents for like 9 years. He was using a online portal to show costs and skipped right through the electric rate section. I had to ask him what he used for kwh. Skum bag.
Also tried to tell me that propane furnaces made when mine was made, around 2003, only last 8-12 years because the government made the manufacturers make them more energy efficient so they used thinner metals, so they only last 8-12 years. Tried to convince me that my furnace only had a couple more years on it to make geothermal look better, again skumbag. I don't think there's any truth to that at all? Furnace should last on average 20 years? Not sure how these guys think they can lie like that. This guy was an igshpa certified installer too.
Vertical certainly is more efficient but in my part of the country cost three times as much as horizontal. I wouldnt worrt about finding a way to fit a horizontal. Just make sure vertical wells are fully grouted and properly spaced. You are also right abiut the furnace with proper maintenance you sgould get 20+ years from it. In my experience and opinion geo is so much better you can replace a 1 year old furnace and ut still makes sense financially.
See Geothermal sights
I don't think conventional furnaces are at 20 years average. Yes they can last 20 or maybe more, but it depends. I believe the average is definitely less than 20 years. Some brands don't last as long as well.
Another thing, I don't think you can get more than a 4 COP in your area, unless your winters are mild. Matter of fact, you might be able to see your contractors Geothermal Calcs that they should have done. That will show you and us alot what your Geo system can do. Ask for it.
I do like Geothermal systems, they are awesome, but sometimes it makes sense to go with the next higher efficient system then the Geo (like Air Source HP).
Your PSC motors (blower) are between 500 to 800 watts. If you know your approximate run time (in hr increments) you can total it up and figure it out.
I hope this helps.
Thanks for the feedback. Arc, you said you don't see me getting more than a 4 COP, please explain. I don't understand that. I thought the outside temp was irrelevant with the geothermal since the ground is at a almost constant temp. So why would the COP vary based on climate? Shouldn't the COP only vary based on the temp of the ground/water in the wells?
the outside temp is mostly irrelevant but as it gets colder your system takes more heat out of the ground so the ground temps will change a few degrees, a knowledgeable contractor should so you expected performance data on loops in your area.
Originally Posted by gregbig2
For example, here in Portland Oregon, a loops EWT(entering water temperature) is usually in the low 40 degree range even though our ground is 52-55 year round. When a system is rated for 4.6 COP that is only if the ground water coming in is 50 degrees so at the realistic conditions of 40 degree incoming water your COP will be 4.1 not 4.6. This still makes geothermal much more efficient than any air source below about a 40 degree outside air temperature and in the summer your realistic EERs could be as high as 25 while the best air source I know of is a 14 EER on an 82 degree day. Don't confuse EER with SEER as air source and ground source heat pumps are rated differently.
Air source vs Ground source.
At 47 degree outdoor temp an air source may be a 4.1 cop and the ground source is let's say a 4.3 COP, now as the temperature drops the air source goes from being a 3 ton unit at 47 degrees to only providing 1.5 tons of heat at 17F with a COP of 2.1 while the ground source has now maybe dropped to 4.1 COP but is still providing 3 tons of heating. There is more than just efficiency to look at because if your air source is a 3 ton unit but it can't provide the three tons of heating needed due to outside air temp dropping and it loosing capacity then the air source shuts down, negating any savings and turns on your backup expensive propane furnace and you are back to where you started. I'm sorry ARC8 but air source 9 times out of 10 can't hold a candle to a geothermal system. Arc8 I. An also tell you with over 20,000 gas furnaces installed in my area installed by my company the average life is aout 20 years.
Not all ground temp are the same. The northern ground temps are colder than the southern region. It also depend on your water flow, hopefully it's correct when installed, which can be caused by the loopfield design as well. And of course, your space temps also affects the final COP of your system.
Originally Posted by gregbig2
If you know which brand and model of equipment, you can find it listed on a performance data on any particular model. Your contractor should be able to show it to you.
It's amazing what each area is capable of doing to the equipment minus the other things by the occupants. They must run more than where you are at.
Originally Posted by SkyHeating
Now about those ASHP. Is that a blank statement across the nation? Around here ASHP can hold water and put out the candle in some instances. I disagree that ASHP's have no competition with Geo's, at least around here they do. Matter of fact, here we usually install plenum heaters, it doesn't matter if it's a Geo or ASHP. We size up systems based on the cooling, not heating; we size systems by the book (ACCA's way).
All and all, if a GEo does not make sense financially (ROI), I usually recommend the second choice ASHP. I wished all could afford a Mercedes, but it is not possible.
I don't see how an air source is close to that of a geo, please explain. Does air source take care of your water heating needs that can be $400-$550 a year with electric or propane? Geo can do some or all of the water heating. Does geo provide constant capacities even in 0f temperatures without backup heat? Yes. Can air source start up with minimal LRA in case of generator operation? No but geo can. In my area and this is not true of all, but a geo can be had for the same and often less after federal tax credit than a two stage or Invertor heat pump. Does air source lose up to half it's efficient at only 17f yes but once again geo may lose 5-10% at most depending on loop.
I didn't realize you were in MN I can see why your furnaces wouldn't last as long but I still see many 40 year old units in my area, very poor efficiency but running yes.
Have you installed geothermal before? I used to do just air source and thought the same things until I really dug deep and had some comparisons from houses with top of the line air source vs even basic geo and the geo in my mild climate usually made sense(biggest restriction is land size) so in colder climates with smaller cooling loads thus according to ACCA more heat strips required the geo took off in average seasonal COP.
Skyheating is right. Geo will always be better..............when installed correctly.