Dual-fuel HVAC vs geothermal heat pump

[strawmyers]

Long story short, HVAC guy says the furnace is toasted beyond what's financially worth trying to fix. Also, AC unit is undersized for the house (PO added 1000ft^2); so I had intended to replace it this summer anyway. Original plans were this:

Bryant Plus 90i furnace
Byrant Preferred series 4 ton HP
Evolution controller

I'll try to portray the following situation without naming prices per forum rules; so bear with me...

So I asked the guy about a closed-loop geothermal HP, and if it was a viable option. He guestimated a geothermal system similar in performance to the above dual-fuel set-up would be roughly double the cost. But...

Considering the 30% tax credit with no cap on the geo HP; it shaves the overall difference in 1/2. What I'm spending in propane right now, the rest of the gap will be bridged in less than 2 heating seasons of not buying propane.

People talk about how expensive a geo HP system is and how its really only worth it for a new construction or if you're going to spend decades in the home... so what am I missing?

What features do you consider essential for a geo HP system? Any specific brands/units you'd recommend that would have similar performance and controllability to the above dual-fuel system?

[hvacvegas]

Long story short, HVAC guy says the furnace is toasted beyond what's financially worth trying to fix. Also, AC unit is undersized for the house (PO added 1000ft^2); so I had intended to replace it this summer anyway. Original plans were this:

Bryant Plus 90i furnace
Byrant Preferred series 4 ton HP
Evolution controller

I'll try to portray the following situation without naming prices per forum rules; so bear with me...

So I asked the guy about a closed-loop geothermal HP, and if it was a viable option. He guestimated a geothermal system similar in performance to the above dual-fuel set-up would be roughly double the cost. But...

Considering the 30% tax credit with no cap on the geo HP; it shaves the overall difference in 1/2. What I'm spending in propane right now, the rest of the gap will be bridged in less than 2 heating seasons of not buying propane.

People talk about how expensive a geo HP system is and how its really only worth it for a new construction or if you're going to spend decades in the home... so what am I missing?

What features do you consider essential for a geo HP system? Any specific brands/units you'd recommend that would have similar performance and controllability to the above dual-fuel system?

If you an afford it, go Geo.
Only because your on propane.
I wouldn't go Geo unless my only options were propane and oil. (personal opinion)

Decades isn't a true statement on the return on investment. Especially with the cost of propane. Decade, I can believe, but thats not factoring the price of the alternative into the mix.

In my area, electric strip heat with heat pump is considerably more efficient than propane.

If you were on natural gas, I'd say go duel fuel.

If you do go duel fuel, maybe the cash you saved and go tri-fuel. Propane/HP, and throw a wood burner in .

[chuckcrj]

Go with Geo. Way better choice than LP. Our electric rates are .115 per KWH and we are seeing 6 to 9 year payback with geo over propane. Good investment.

[motoguy128]

If you're on propane and have plenty of land for geo and can afford it.. go geo. Make sure they put in enough loops. Better to have more than you need, especially since soil can take some time to settle and achienve full heat transfer. Get a good load calculation done. You defnitely don't twant to be oversized... sicne it increases you installation costs significantly.

My only concern is long term. With air sourced inverter equipment closing the gap on efficiency, 15 years from now, when you're ready to upgrade, will geothermal still be the most cost effective?

[grasshopper]

Around here alot go geo with lp furnace to get duel fuel offpeak electric rates reduced about 45% of the regular rate. Between the tax credits, energy rebates and energy savings..... we are seeing way less the a decade for return.... depending on the home.

[beenthere]

Did his price guess include the wells.

[strawmyers]

He didn't specifically mention wells (didn't realize they were needed with a closed-loop system); but his statement was: "By the time you're all done, you'd probably be looking at around$xxxxx." ... so I assume that was inclusive. I do know that included the loop system as he did say that.

What is a minimum linear feet of loop for a 2400-2800 ft^2 house? There's about 1/2 an acre beside the house that could be utilized. The rest of the yard either has the septic finger system or is wooded.

What options do you guys like in a geo HP?

[hvacvegas]

He didn't specifically mention wells (didn't realize they were needed with a closed-loop system); but his statement was: "By the time you're all done, you'd probably be looking at around$xxxxx." ... so I assume that was inclusive. I do know that included the loop system as he did say that.

What is a minimum linear feet of loop for a 2400-2800 ft^2 house? There's about 1/2 an acre beside the house that could be utilized. The rest of the yard either has the septic finger system or is wooded.

What options do you guys like in a geo HP?

Theres alot of variables that determines loop length. one of which is your soil content.

Here, we see alot of 250-275' deep vertical holes, 1 hole per ton.

[tigerdunes]

Strawmyers

Before I purchased and installed a Geo HP system, I would look at and price Carrier's new high eff GreenSpeed HP system.

Then weigh your costs, tax credits, efficiency and payback between the two systems.

IMO

[Stamas]

If you go Geo consider adding a non-pressurized flow center to the budget.

[SkyHeating]

Geo all the way, where are you located? I don't think I saw it in your post, some places do wells at 200-250 ft per ton and others(like where I am) do horizontal loops at 600+ feet of linear pipe per ton. I just did a propane to geothermal conversion, check my youtube channel for Mark L Propane to Geothermal video, it will give you a good idea of what you are looking at if your are going with a horizontal loop. It is a 5 ton system, depending on your area and house you may need a 3 to 5 ton system. Mark was spending about $4,500 a year on propane in a mild year, this year has been fairly harsh and bills are estimated at $1,200 yearly.

As for features, go two stage with a variable speed blower, make sure they add a DHW(desuperheater) feature if possible. Make sure the installer has done this work before and is IGSHPA certified. Brands to look for are WaterFurnace, Hydron module/geocomfort and Comfortmaker. As you have probably read, installation is HUGE, I honestly wouldn't care what equipment was in my house so long as it was done with a proper loop and startup.

[strawmyers]

I live in central Indiana. The video was very helpful; especially the part showing the "race track" trench. When I read 600 linear ft/ton, I thought there's no way they're going to make a loop that large in the open part of my yard because I had assumed the tubes needed a few feet of space between one another. The current furnace is 5 ton. If its a 1:1 transfer between what is needed for a geo HP versus a standard furnace, that's 3000 linear feet. I think that will be viable with a "race track" in my yard. Thanks for the input!

[SkyHeating]

I live in central Indiana. The video was very helpful; especially the part showing the "race track" trench. When I read 600 linear ft/ton, I thought there's no way they're going to make a loop that large in the open part of my yard because I had assumed the tubes needed a few feet of space between one another. The current furnace is 5 ton. If its a 1:1 transfer between what is needed for a geo HP versus a standard furnace, that's 3000 linear feet. I think that will be viable with a "race track" in my yard. Thanks for the input!

The loop is not a 1:1 it is dependant on the Manual J calculation for your house. A 5 ton furnace means 5 tons of airflow it is probably a 120K BTU furnace while a 5 ton geothermal system will be between 52 and 64K BTU's of heat. A loop is sized based on size of geothermal unit, deep earth temperatures, ground lag time and heat loss/gain of home.

Just for comparison, in Indianapolis IN with a 55K BTU heat loss I am showing a 4 pipe racetrack length of 935 ft per line for a total of 4000' give or take, if you were to do a 6 pipe racetrack I am showing 710 ft per line for a total of about 4300', this assumes a silt/clay soil. This trench sizing could still vary greatly from what I put into my software since I have no idea what Indiana weather is like and if you use wells or horizontal.