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?
First cost and design cost has always been an issue with GSHP. If its cheap and easy to put pipe in the ground where you are, GSHP is great, but you need to make sure you have enough pipe in the ground. That's not easy. You need someone who understands local hydrogeology well.
ASHP performance on an annual basis is worse than GSHP but closer than you'd think. ASHP performance is also easier and cheaper to accurately predict. If you're looking to combine water heating I'd look at Daikin Altherma or the hydronic attachments to mitsubishi's city multi system. Both of those systems have good low ambient performance.
I think something like the Altherma would be a cheap and easy "bolt on" solution to your energy cost issue by adding a hydronic coil to the existing propane furnace system (probably in place of your existing DX cooling coil). On the DHW side you could put the Altherma DHW tank in a preheat position in series with your existing and run your recirc to the Altherma tank if youre not comfortable with peak day performance and want to minimize your capital costs now.
I hope I helped!
Feel free to contact me and other users here for more detailed assistance within the context of a contract. Advice and opinions are provided here "as-is" without any warranties, guarantees or acceptance of liability for use, misuse, or accuracy of advice given. (Gotta keep my legal team off my back at work.)
Interesting, very interesting. I googled Altherma and it looks like it's a inverter heat pump boiler? I'm trying to understand how that would work with my force air ducts though? Use a water to air heat exchanger? Or would I have to put those fan coil units in each room? Thanks
Sorry, I re-read your post and you explained it already, add a hydronic coil to the propane system. So I'd use my existing ducts. I could probably easily add a zone to the basement also with a fan coil. I will contact a local Daikin dealer, thanks.
If you went with Mitsubishi, you'd put small DX fan coils in each room and a hydronic heat exchanger on a recirc loop with domestic. They have a product called HydraDan that's just like Altherma but not available in the US.
Make sure you understand how the Altherma system wants to operate on the hydronic side before doing this. It looks more like a commercial two-pipe hydronic system to your terminal equipment, except add on the complexity of DHW priority during both cooling and heating. It will affect the piping layout. Basically you want to keep the tees going off to the Daikin DHW tank close to the hydrobox so that there isn't a big cold slug when it changes over for DHW priority in the summer and a big hot slug when it goes back into cooling once the DHW call is satisfied. Also I would suggest using three port valves on your water to air coils so that you keep a decent mass of water moving through the refrigerant to water heat exchanger. Speaking of those coils, size them based on 105F entering water in heating for best performance.
Maybe your area is much different than mine but an Altherma costs MORE than geothermal where I am and does not receive a tax credit. I can put in a vertical bore or horizontal bore(about $18 per foot in my area to drill) for the cost of an Altherma and still have higher performance. Just something to consider.