Mini Split Heating at -8F

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NorMi

Member
Nov 18, 2021
111
Northern LP, MI
Mini Split Heating at -8F

In another recent thread, the subject of mini splits and heat pumps came up tangentially in a heating context. I have been heating for two seasons at my new house with a mini split, and this may be one of the last times I can report on cold weather performance with the system. Overnight forecasts were for -1F, but with clear skies we actually reached -8.3F this morning. First I will give a little history on how we did the mini split and why, and then give you the lived experience results for one nice, cold day in January.

Why a Mini Split in Zone 5A?​

I moved here from zone 6A in NE Ohio where I used a mini split for bedroom heat and cooling, so I had some experience with normal 5F rated units, which surprised me when they could keep up even in negative temperatures without much trouble. We moved in 2020, into a old farmhouse that has been renovated. It is a 1900 ft2 1.5 story, with a kitchen, bath, dining room, living room downstairs, and 3 bedrooms and a master bath upstairs. Zone 5A is considerably colder in northern Michigan, but new mini split units were also rated to -22F.

Farmhouses from the turn of the last century are usually poorly insulated, over glazed, and usually do not have central heating - this was no exception. When they renovated, they added good insulation, double pane windows, electric baseboard heat and a 25-35K BTU direct vent propane fireplace in the living room. That’s plenty of heat. The house came with about half a 500 gallon tank full of propane, so we started last season with that and a few weeks in, I started calling around to get the tank filled. It was impossible – each vendor wanted an original bill of sale for the propane tank before they would fill it, or to sell a new tank to replace the perfectly fine existing one. Propane pricing has historically been very volatile, so planning and budgeting with it is not very accurate either. Most said they would sign me up at $1.60/gallon and refills at $2/gallon after they sold me a tank, which was historically pretty rock bottom pricing in real value adjusted terms. Instead I filled two 100lb. tanks to have on hand for emergency backup, ran the 500 gallon empty and disconnected it permanently. The general attitude and ethics of these companies meant propane was not a viable primary heating source in this area.

Over the long term, I knew I wanted to heat with wood as either primary or supplemental in the house, and wood-only in the barn/shop. There is enough wood on the property to heat the shop occasionally and supplement the house if I added some wood stoves/furnaces in those locations. We discussed this for several months if we wanted to go all in on the wood right away, but we decided it probably wasn’t the best all-round full year solution for ease of use right off the bat. Since nothing was stacked, we’d need to buy seasoned wood for year one as well, local costs for that hovered in the range of $225-250/cord.

Electricity rates where we moved from were 13.5 cents/kWh delivered, and here they were an eye-popping 17.5 cents/kWh delivered. Armed with monthly average climate data, all the pricing figures, efficiency estimates for the propane fireplace & potential wood stoves, plus mini split COP charts, I could start making some estimates. It was fairly fuzzy math at that point since I had no idea what efficiency the fireplace was running at, and it was still early in the season – the propane ran out on November 15th. From my estimates, it would be fastest and cheapest up front to install a mini split on year one to serve the downstairs areas, and it would be only slightly more expensive vs. wood or propane to run based on what I thought I knew at the time…

Apples to Apples​

In order to get a good handle on heating costs, I needed to know how much each system cost to operate in a comparable way. I wasn’t going to have the luxury of whole heating seasons to compare, so I needed something more within reach. I decided to determine the heating cost of each fuel source I used the first year based on how much energy I used per each heating degree day (HDD). This gave me a nice way to compare costs, as heating degree days quantify how much heat is needed, so by measuring how much fuel I used each period, and comparing that to the number of heating degree days in that period, I could get a good solid estimate for cost/energy per a heating degree day, which is a levelized figure – perfect for comparison. I heated for 71 days with propane, 27 days on electric resistance heat waiting for parts shipments, and the remainder of the season on the new mini split. Propane I was using 3.04 kWh of input energy per HDD, resistance electric heat used 2.04 kWh per heating degree day, and the mini split averaged 0.57 kWh per HDD.

Partial Year Cost Comparisons​

With that data, I could then compare the cost of each type of heating I used so I could get an estimate of how much money each HDD would cost me. Using HDD meant how cold it was during each period didn’t majorly effect the cost comparison much, but since the mini split was used in the coldest part of the year, its estimates here are both more accurate and higher than they would be relative to the others if each type of heat was used for a full year. The electric resistance baseboard and propane both benefited from being tested in mild temperature conditions only. On propane the “first fill” rate was a very cheap kWh of energy – $1.6/gallon, each gallon is 27.98 kWh of energy, so each kWh cost only 5.7 cents! Since each HDD used 3.04 kWh on propane, each HDD cost me 3.04 x $0.057 = 17.3 cents per HDD. On the normal cost fill at $2/gallon the cost is 7.15 cents per kWh, and a HDD cost of 3.04 x $0.0715 = 21.7 cents per HDD. Electric baseboard used only 2/3 the kWh/HDD vs. the propane fireplace, but each kWh is much more expensive at 17.5 cents. This meant that 2.04 x $0.175 = 35.7 cents per HDD make it very expensive indeed! The mini split really kicked in for those free therms, and even though each kWh is expensive at 17.5 cents each, it used them very judiciously for a final price of 0.57 x $0.175 = 10 cents per HDD, by far the cheapest even with the dirt cheap propane last year. Keep in mind this is the seasonal average, from December until heat stopped being used around April/May.

Forced Austerity and Comparing Incomparables​

If you’re very very keen, almost immediately you’ll see that those numbers sound… off. Mini splits are not that cheap to run especially on expensive power! How did you use so much propane! Etc, etc. The devil is in the details! Each system was helped or hurt by different factors, because each system was used very differently in practice.

Propane​

Propane was our first heating source for the year last year. It only has one outlet, the fireplace in the living room with a blower that circulates the heat in that room. It is probably not a particularly efficient unit, although I couldn’t find specs on it anywhere - it’s a Heatilator GCDC80 with a propane orifice installed. It has a neat RF remote control you carry with you so the room you’re in is the one that sets the temperature. In order to heat a whole farmhouse with this method means the living room has to get hotter than you’d otherwise like it so the heat gets to all the places you want it. Zoning is nearly impossible with such a heat source. The only thing we did was keep the two unused bedrooms upstairs closed off. These factors hurt the propane results in this house.

Electric Resistance​

We started using the baseboards while we were waiting for the mini split and parts shipments to come in. The propane ran out sooner than I had anticipated. Knowing this was going to stab a knife into my pocketbook, we made some changes to our heating use to compensate. Each room has its own thermostat and its own baseboards, which meant we could heat each room only to what was needed. We split the downstairs in half – kitchen dining room and bath in one zone, and the living room in another zone. The master bedroom became its own zone as well. This zoning in combination with electric baseboard’s innate 100% efficiency in turning kWh into heat inside the house with no exhaust component, meant we could reduce the kWh/HDD from 3.04 on propane down to 2.04 on electric.

Mini Split​

Mini Splits and heat pumps in general are kind of like cheating. The one we have does a 3.8 COP at 47F outdoor temperature. That means we get 3.8 kWh of heat in the house for every 1 kWh of electricity we use. This coefficient of performance drops gradually until it reaches unity at -22F outdoors, and the mini split is then no better than the baseboard. We can use the cost of the electric baseboard (COP=1) relative to the cost of the propane per HDD to calculate at what COP we should switch from the mini split to propane for heat. As COP 1 costs us 35.7 cents/HDD and propane at $2/gallon costs us 21.7 cents/HDD, at those prices we should switch from the mini split to the propane any time the mini split COP is less than 35.7/21.7 = 1.64. If propane is cheaper, the COP where we should switch is higher, and if propane becomes more expensive, the COP where we should switch is lower. Propane is more expensive than any electric heat in this house once it passes 35.7 cents/HDD, 11.7 cents per kWh, or $3.29/gallon. For our mini split, a COP of 1.64 from last years pricing indicates a cut over temperature of about -2F outdoor temperatures for optimum heating cost. This year there is no optimum cutover temperature, as propane prices have exceeded its break-even price relative to electric resistance heat.

The next major factor that effected the mini split seasonal performance data was the fact that the system is undersized relative to the whole house. The one we installed was meant to be sized for only the downstairs, and as such it is a 2.25 Ton (27K BTU) unit. This is all we use for heat the past two years, even though it is not “large enough”. Instead of burning more kWh to keep the house warm, we only heat the room(s) we are using and reduce the temperatures of the other zones to make sure we keep the main room the right temperature. This undersizing means we used a forced austerity model for zone demand, and that also means we can never spend more than ~$13/day or 72 kWh/day for heat, no matter what. The system is maxed out at that point, so instead of using more power, we cut the temperature of the peripheral room zones to compensate. This has a major impact on how much cold weather days cost, at the expense of losing excessive bourgeois comforts.

How it Works at -8F​

Now, for the main event. How does it feel in each room at cold temperatures? Yesterday, it was about 10F outside, so I needed to make no special zoning controls as the mini split is large enough at those temperatures. All I do is close the bedroom off during the day and open it an hour or so before bed. This morning at -8F, there is not enough heat. As temperatures drop below 5F, I have a set zoning response that I do. First, I close off the upstairs stairwell with a curtain. This keeps the entire downstairs comfortable down to around 0F, +/-. The sacrifice is the bedroom is no longer in our preferred range of 60-62F, it drops to ~55F which is a bit cool. This means it takes longer to heat up in the evening. Below about -5F it wouldn’t be able to stay warm enough for our preference upstairs at night. To account for this, in the evening, we would open up the stairwell and the bedroom door, and in turn close off the kitchen/dining/downstairs bath zone and simultaneously reduce its set-point temperature. This puts more available energy in the living room/stairwell/bedroom zone. Keep in mind we zone this way because it is a 2 story house, with only two indoor heads - one 18K BTU in the living room and one 12K BTU in the dining room.

Here is how it looks in practice:
Screenshot 2022-01-07 at 12-35-30 Emoncms - graph.png
You can see from the chart above, that shortly after 7:00AM, I started laying off heat demand in the kitchen and bedroom zones to make the living room zone more comfortable. You can also see the pronounced dips when defrost cycles take place, which noticeably cools the room(s).

Another commenter mentioned the outlet air temperatures of the indoor heads as a potential comfort factor, so I threw a temperature sensor gauge in the living room head this morning to give you all some data on how hot that air feels coming out of the unit The fan is off during the defrost events but the air "falling" out of the units is quite chilly indeed:
Screenshot 2022-01-07 at 12-41-11 Emoncms - graph.png
 

stoveliker

Minister of Fire
Nov 17, 2019
5,327
Long Island NY
Wow. Fantastically informative write up. Thank you!
 

NorMi

Member
Nov 18, 2021
111
Northern LP, MI
There was a major worldwide Starlink outage this morning, so I had some time on my hands.... 😅
 

begreen

Mooderator
Staff member
Nov 18, 2005
94,654
South Puget Sound, WA
Thanks for the detailed report. You're lucky wood and propane are relatively cheap still.
What temperature logging equipment are you using? What is the make and model of the system?
 

NorMi

Member
Nov 18, 2021
111
Northern LP, MI
Those were last year's (2020-2021 season) prices (225-250 wood and $2 propane)... this year, I know Tractor Supply has propane at $4.37, they are always high but a good indicator, last year they were around $2.40 when I got quotes from other vendors, and they are one of the only places local that isn't ashamed to post the price publicly online... Quality wood seems to be inching towards 300 too! At those prices electric is cheaper at all temperatures unfortunately, but even it bumped up to 18.1 cents/kwh delivered this year.

For data logging and automation I use OpenEnergyMonitor and HomeAssistant. The hardware PCB's and software are all open source and I use no cloud based components (they both have cloud options/features). The charts are screenshots of OpenEnergyMonitor's emoncms data viewer. It runs on a customized raspberry pi with a arduino-based hat they sell as a package as an "EmonPi". I use their battery powered EmonTH for temp/humidity monitoring remotely and it also ties in nicely with my OpenEVSE for our car. I use EmonTX's on remote off grid solar installs around the property to monitor and trigger events based on power events and output. I use routed IPv6 with dynamic DNS to access the system remotely through a VPN tunnel.
 

begreen

Mooderator
Staff member
Nov 18, 2005
94,654
South Puget Sound, WA
Those were last year's (2020-2021 season) prices (225-250 wood and $2 propane)... this year, I know Tractor Supply has propane at $4.37, they are always high but a good indicator, last year they were around $2.40 when I got quotes from other vendors, and they are one of the only places local that isn't ashamed to post the price publicly online... Quality wood seems to be inching towards 300 too! At those prices electric is cheaper at all temperatures unfortunately, but even it bumped up to 18.1 cents/kwh delivered this year.

For data logging and automation I use OpenEnergyMonitor and HomeAssistant. The hardware PCB's and software are all open source and I use no cloud based components (they both have cloud options/features). The charts are screenshots of OpenEnergyMonitor's emoncms data viewer. It runs on a customized raspberry pi with a arduino-based hat they sell as a package as an "EmonPi". I use their battery powered EmonTH for temp/humidity monitoring remotely and it also ties in nicely with my OpenEVSE for our car. I use EmonTX's on remote off grid solar installs around the property to monitor and trigger events based on power events and output. I use routed IPv6 with dynamic DNS to access the system remotely through a VPN tunnel.
Thanks. Those prices are closer to ours for wood and propane. What is the make and model of the mini-splits?
 

Brian26

Minister of Fire
Sep 20, 2013
680
Branford, CT
Awesome write up. Efficiency Maine has a great fuel cost comparison website online. You can input your own data but the default data is recent state tracked fuel prices. The savings with a heat pump are pretty crazy right now in New England with current fuel costs especially with propane. The website currently has default fuel price data from 01/05/22 so its very recent. The website is showing the estimated total winter heating costs this winter for each fuel. Its crazy how a propane furnace will cost you $3k more this winter.

Heat Pump $1795
Propane boiler $3909
Propane Furnace $4730
Electric Resistance $5258


Another huge plus with heat pumps is electricity prices are way more stable than fossil fuels. Electricity is heavily regulated in most states and here in CT the rates are only adjusted on Jan 1st and June 1st. That rate adjustment has to be approved by the state utility authorities and they usually always settle for an increase less than what the utility requested. So right now your fuel cost in CT for a heat pump is a fixed price until June 1st. I just saw a billboard for heating oil I drive by all the time jumped 25 cents a gallon in the last week or so.

Cool monitoring data as well. I'm on net metered solar and have been heating exclusively with 2 cold climate mini splits for about 3 winters now. I have electricity monitors on a ton of stuff including the mini splits. I also log a ton of temperature data around the house using an Acurite sensor hub. I use an Efergy engage hub for the electricity monitoring.

Here is a snapshot of some the sensors. Its currently 19 degrees here and both splits are putting out 100+ supply air. On the electricity chart you can see after midnight when temps drop fast the inverter will step up to the exact load as the temperature drops.

Screenshot_20220108-055112_My AcuRite.jpg Screenshot_20220108-045942_Monitor.jpg
 
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NorMi

Member
Nov 18, 2021
111
Northern LP, MI
Thanks. Those prices are closer to ours for wood and propane. What is the make and model of the mini-splits?
I'm using a Bosch Max Performance 27K BTU ODU paired with the 12k & 18k IDU's, it does 28K BTU heating. They have another type also that is cheaper and only rated to -13F. They call the entire lineup "Climate 5000" and the low temperature ODU's are the Max versions, they do the rated BTU down to -5F before output drops off. This one was $3300 last year for the full install, but they've bumped prices up since then it looks like.
 

NorMi

Member
Nov 18, 2021
111
Northern LP, MI
Awesome write up. Efficiency Maine has a great fuel cost comparison website online. You can input your own data but the default data is recent state tracked fuel prices. The savings with a heat pump are pretty crazy right now in New England with current fuel costs especially with propane. The website currently has default fuel price data from 01/05/22 so its very recent. The website is showing the estimated total winter heating costs this winter for each fuel. Its crazy how a propane furnace will cost you $3k more this winter.

Heat Pump $1795
Propane boiler $3909
Propane Furnace $4730
Electric Resistance $5258


Another huge plus with heat pumps is electricity prices are way more stable than fossil fuels. Electricity is heavily regulated in most states and here in CT the rates are only adjusted on Jan 1st and June 1st. That rate adjustment has to be approved by the state utility authorities and they usually always settle for an increase less than what the utility requested. So right now your fuel cost in CT for a heat pump is a fixed price until June 1st. I just saw a billboard for heating oil I drive by all the time jumped 25 cents a gallon in the last week or so.
I used that website last year, great resource! It was a good starting point, but I wanted to have data for my house specifically and my actual usage numbers did come back quite a bit differently last year on the costs/ratios at that time. The stability of electricity prices is a nice bonus for sure when you're budgeting it, usually the reason you have to redo cost calculations is because of continuous swings in the other fuels.

My dad used to do this when I was a kid, he'd take the cost of propane/electric/oil and use the efficiency of each system to pick which one to use based on cost x efficiency. I did that at first with a "guess" on the propane fireplace efficiency but it wasn't an accurate method - even if I had the manufacturer efficiency numbers. It doesn't take into account actual use characteristics, other losses, or zoning... I never saw anyone do the heating degree day method I used, but it seems to work for me rock solid on getting strong estimates from a smaller snapshot of data from my actual house performance. The good news is if you can just switch between systems in isolation for short periods of time, it is easy to get a really strong data set for your own house, which you can then use as the formulas to update a cost spreadsheet in real time just by inputting the current prices.
 

Nate R

Member
Nov 5, 2015
84
Wisconsin
Great info! Thanks for sharing this and your logging setup.
 

NorMi

Member
Nov 18, 2021
111
Northern LP, MI
I should mention some on to get degree days, you can calculate yourself from your personal weather station data, or use a site like https://www.degreedays.net/ to generate them for you from a local weather station or closest airport. Then all you need is the quantity of fuel used. For propane tanks you can use the fuel indicator as a percentage of full, which is what I used, and then converted that into gallons used, you could do the same with fuel oil. The best quality measurement for liquids will come from doing it with a full tank of fuel as a known starting point and using the refill gallons from the truck on the next fill just like if you were doing MPG calculation for your car. Then to get data for the whole period, just sum the degree days up and calculate the ratio of fuel energy/heating degree days.
 

Brian26

Minister of Fire
Sep 20, 2013
680
Branford, CT
I know many people think these units dont work well in subzero temps but there have been big improvements in the last few years. Last year Mitsubishi released a deluxe version of their popular H2i Hyper Heat. It has a huge increase in cold weather performance and efficiency over prior models. They have especially made a really big jump in cold weather coefficient of performance. They are rated to 100 capacity at -5 and have cop's above 2 even at -13.

Remember these are cop's at max capacity when the compressor is at max. The cop increases significantly when the compressor runs at lower speeds. For example at half load at 17 degrees the unit could be achieving a COP of 3.2

MUZ-FS12NA-U1

Capacity and COP at max speed

47 degrees. 21000 btu COP 4.24
17 degrees. 17,410 btu COP 2.74
5 degrees. 14690 btu COP 2.24
-5 degrees. 12300 btu. COP 2.24
-13 degrees. 11000 btu COP 2.08

Its interesting that this unit has almost twice its capacity available at 47 and has almost 18k at 17 degrees. It seems it was specifically rated for its capacity at -5. Its also impressive even at -13 its operating at a cop above 2 for an effective efficiency of 208%. That's double the efficiency of any fossil fuel heat even at -13.


Here is the submittal for the unit with all the specs.

 
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EbS-P

Minister of Fire
Jan 19, 2019
3,038
SE North Carolina
Great write up. Thank you! Always on internet is a huge time suck.

I got a mini split quote and was dissuaded from getting a multi head unit. It was supplemental heat for a basement the winter and cooling the kitchen and living area in the summer. We remodeled and added 500 sq ft in the basement (we converted a large two car garage and replaced the garage door with an insulated all glass garage door). Current heatpump, 3 ton two stage with leaky ducts, struggled before the renovation when temps dropped below 25 and resistive strips start to come on if we didn’t get a significant warm up during the day to recover heat it would run 80% duty cycle.

Are both heads always run at the same time?

Evan
 

NorMi

Member
Nov 18, 2021
111
Northern LP, MI
The single zones will usually perform better, but they also cost more for a complete home type install. I split the difference and thought I would go with either 2 mutizones over the long term, or two multis and a best in class single zone or something. At the extremes I have tested, I can put the dining room one in "FP" which is the lowest temp setting at 46F I think it is, and leave the other one running full blast. It basically shuts off that unit in the dining room, without letting the pipes freeze in the kitchen. Otherwise the lowest thermostat setting is 62F on mine. *You can turn them on or off independently. Also I don't know if this is common, but in cold temperatures the numerical setting on the head units is totally worthless, probably because I'm heating too large an area with too small of an output curently... I use z-wave IR controllers and a PID loop to set target temperatures on the mini splits. This also prevents users like me from trying to make huge swings in the temperature settings pushing the compressor to max speed, which as noted hurts COP. So my PID loop from my home automation only moves the temp setting 1F at a time, slowly to try to keep it at maximum possible performance.
 
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sloeffle

Minister of Fire
Mar 1, 2012
1,019
Central Ohio
Great write up.

In your write up you mentioned

Over the long term, I knew I wanted to heat with wood as either primary or supplemental in the house, and wood-only in the barn/shop. There is enough wood on the property to heat the shop occasionally and supplement the house if I added some wood stoves/furnaces in those locations. We discussed this for several months if we wanted to go all in on the wood right away, but we decided it probably wasn’t the best all-round full year solution for ease of use right off the bat. Since nothing was stacked, we’d need to buy seasoned wood for year one as well, local costs for that hovered in the range of $225-250/cord.
Not to send you down a further rabbit hole. ;) Have you compared the costs of heating with wood vs your mini-split ?
 

EbS-P

Minister of Fire
Jan 19, 2019
3,038
SE North Carolina
Great write up.

In your write up you mentioned


Not to send you down a further rabbit hole. ;) Have you compared the costs of heating with wood vs your mini-split ?
Here you can figure cost.

Really you need to know the COP of the unit at the outdoor temp you are interested in. Those details can be changed in the website above.
 

sloeffle

Minister of Fire
Mar 1, 2012
1,019
Central Ohio
Here you can figure cost.

Really you need to know the COP of the unit at the outdoor temp you are interested in. Those details can be changed in the website above.
I'm well aware of that site and others like that. The OP however figured it out specifically for his heating zone ( HDD ) and house.
 
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Brian26

Minister of Fire
Sep 20, 2013
680
Branford, CT
If anyone wants to read up on how these units are able to achieve their cold weather performance here are some links below. They are using enhanced vapor injection compressors which was invented by Mitsubishi Electric.

Artic who makes a cold climate air to water heat pump has a good quick explanation here.


If you really want to read into it Oak Ridge National Labs as a 86 page High Performance Cold Climate Heat Pump Report. They reference Mitsubishi with inventing the technology and explain the hyper heat system well in the report.

 

aaron1

Member
Oct 9, 2012
179
Poughkeepsie, NY
I know many people think these units dont work well in subzero temps but there have been big improvements in the last few years. Last year Mitsubishi released a deluxe version of their popular H2i Hyper Heat. It has a huge increase in cold weather performance and efficiency over prior models. They have especially made a really big jump in cold weather coefficient of performance. They are rated to 100 capacity at -5 and have cop's above 2 even at -13.

Remember these are cop's at max capacity when the compressor is at max. The cop increases significantly when the compressor runs at lower speeds. For example at half load at 17 degrees the unit could be achieving a COP of 3.2

MUZ-FS12NA-U1

Capacity and COP at max speed

47 degrees. 21000 btu COP 4.24
17 degrees. 17,410 btu COP 2.74
5 degrees. 14690 btu COP 2.24
-5 degrees. 12300 btu. COP 2.24
-13 degrees. 11000 btu COP 2.08

Its interesting that this unit has almost twice its capacity available at 47 and has almost 18k at 17 degrees. It seems it was specifically rated for its capacity at -5. Its also impressive even at -13 its operating at a cop above 2 for an effective efficiency of 208%. That's double the efficiency of any fossil fuel heat even at -13.


Here is the submittal for the unit with all the specs.

wow, that's fantastic! i was thinking about geothermal, but the new ASHPs are so good, I think it might make more sense. The only downside is there is more maintenance on the mini splits. Not sure how big of a pain that would be.
 
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sloeffle

Minister of Fire
Mar 1, 2012
1,019
Central Ohio
wow, that's fantastic! i was thinking about geothermal, but the new ASHPs are so good, I think it might make more sense. The only downside is there is more maintenance on the mini splits. Not sure how big of a pain that would be.
I have geothermal, if was doing something today I'd go ASHP all the way. The COP's of ASHP's are about as good as a geo unit these days. Even better when temps are in the 40's and 50's on a few of the units.

Geo units seem so overpriced these days it's ridicoulous. I've heard of people paying 30 - 40k for an install. I'm sorry, but you'll never get your money back at that price. They still use energy to run that you have to pay for after the steep install cost. Geos require maintenance too, a few months ago I had to get a capactior replacaced, and you have to check loop pressures a few times a year. Luckily the capactior was still covered under warranty by Waterfurnace.
 

aaron1

Member
Oct 9, 2012
179
Poughkeepsie, NY
I have geothermal, if was doing something today I'd go ASHP all the way. The COP's of ASHP's are about as good as a geo unit these days. Even better when temps are in the 40's and 50's on a few of the units.

Geo units seem so overpriced these days it's ridicoulous. I've heard of people paying 30 - 40k for an install. I'm sorry, but you'll never get your money back at that price. They still use energy to run that you have to pay for after the steep install cost. Geos require maintenance too, a few months ago I had to get a capactior replacaced, and you have to check loop pressures a few times a year. Luckily the capactior was still covered under warranty by Waterfurnace.
Thanks for the input. I was quoted a 6T geothermal unit from Dandelion for $23k after rebates and Fed. tax credit. That doesn't seem bad as far as geothermal is concerned, but it's only a 2-stage compressor (100% or 70%) which seems like it wouldn't be as efficient as an ASHP that can modulate down a lot more. Also, my old ducting is pretty dodgy I think. There's no return upstairs at all, which might make cooling pretty uneven. I thought the minisplit option might be more efficient and should be less than $23k. Supposedly the new ASHPs should have a pretty long life.
 

sloeffle

Minister of Fire
Mar 1, 2012
1,019
Central Ohio
Thanks for the input. I was quoted a 6T geothermal unit from Dandelion for $23k after rebates and Fed. tax credit. That doesn't seem bad as far as geothermal is concerned, but it's only a 2-stage compressor (100% or 70%) which seems like it wouldn't be as efficient as an ASHP that can modulate down a lot more. Also, my old ducting is pretty dodgy I think. There's no return upstairs at all, which might make cooling pretty uneven. I thought the minisplit option might be more efficient and should be less than $23k. Supposedly the new ASHPs should have a pretty long life.
I have a Waterfurance 5 series ( Envision when I bought it ) that has a 2-stage compressor also. The compressor on the 7 series has infinite speeds, big money though from talking to my service guy. Mine runs at 100% ( 4 tons ) and 65% ( 2.5 tons ) I believe from what the installer told me. It's have never run above stage 1 in the summer and runs in stage 2 every once in awhile when I run it during the winter. I have a wood burning furnace that I use to heat my house most of the winter. $300+ electric bills all winter don't sound that great.

Another thing to keep in mind with a geo install is that it easily be screwed up by not having the right installer. My system has 2400' of pipe in the ground. I had quotes that had 600' of pipe. In my area the rule of thumb is 600' of pipe per ton. Head over to geoexchange if you want to read some of the horror stories of folks with very high electric bills because their aux heat is constantly running. Not having a unit outside is nice because you know it isn't going to get "beat up" by the elements.

If you are concerned about duct loses also I'd go probably lean more towards a mini-split.
 
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UpStateNY

Feeling the Heat
May 4, 2008
435
Catskill Mountains
The Maine calculator Prices and Efficiency are way off in my situation. I have a 3 year old Navien Propane Combi Boiler at $1.76 a gallon of propane. I have brand new Fujitsu mini-split ductless heat pumps at $0.15 per Kwh. I burn propane most of the winter. When its warmer than 35F, I turn on the ductless heat pumps. So far I have burned this fall/winter 561 gallons of propane ($987) and approximately $100 of electric.
 

maple1

Minister of Fire
Sep 15, 2011
10,941
Nova Scotia
The Maine calculator Prices and Efficiency are way off in my situation. I have a 3 year old Navien Propane Combi Boiler at $1.76 a gallon of propane. I have brand new Fujitsu mini-split ductless heat pumps at $0.15 per Kwh. I burn propane most of the winter. When its warmer than 35F, I turn on the ductless heat pumps. So far I have burned this fall/winter 561 gallons of propane ($987) and approximately $100 of electric.

If your Fuji is one of their most efficient cold climate models I would have no issue moving that 35f 'crossover' point down to 15f.
 

Brian26

Minister of Fire
Sep 20, 2013
680
Branford, CT
The Maine calculator Prices and Efficiency are way off in my situation. I have a 3 year old Navien Propane Combi Boiler at $1.76 a gallon of propane. I have brand new Fujitsu mini-split ductless heat pumps at $0.15 per Kwh. I burn propane most of the winter. When its warmer than 35F, I turn on the ductless heat pumps. So far I have burned this fall/winter 561 gallons of propane ($987) and approximately $100 of electric.
The average price of propane is $3.49 a gallon in NY according to the EIA. You must have locked into a lower rate? Someone I know in CT was just charged $4.25 a gallon for propane.