Alternative heat source, minisplits for real?

[Highbeam]

So we had another one of our random burn bans yesterday so I was unable to burn my stove despite air quality in the green "good" for my area. I hate the bans because I think they are not compliant with the law but I took this opportunity to do some checking on my home's systems.

It was 25 degrees F last night. Even down into the single digits I am consistently burning under 60# of wood per day to keep the joint very warm inside. If I conservatively assume 80% actual efficiency that means on average 17,200 btu per hour. Seems low I thought. Heck that's just 5000 watts. It is very rare that we get below 20 degrees in my location. 95% of the year I burn just 40# a day (a single load of softwood) which comes out to 11500 btu per hour.

My "primary" heat source is a whole bunch of electric resistance wall heaters. This old house has never had ducts or radiators. It has a bunch of 20 amp, 240 volt, 12 gauge circuits that feed these wall heaters. I've replaced 2 of them during remodeling with pick-a-watt 2250 watt units. There is one of these circuits that is unused as I haven't found a good place to put the heater.

Due to the burn bans I had a chance to test them. I flipped two of the breakers on for the first time in a decade and really should have blown them out first. The dust stinks! Those two heaters in the main living area held 70 degrees and only cycled about 50% of the time so I was actually holding 70 with just 8000 btu per hour.

I have always liked the Mitsubishi hyperheat minisplits but the inside unit is uglier than my princess stove! The 18kbtu model inside unit is just 38" wide and apparently would be enough for 100% of my heating. It's supposed to make 20,000 btu per hour of heat down to 5 degrees. All from a silly small 15 amp circuit. Plus AC and I would keep the old wall heaters as backup backups. I just can't imagine running ductwork in this single story home. It would all be in the attic.

Is this correct? Did I miss anything in my heat load testing theory? Does the circuit for these things need to be a 4 wire 12/3 circuit? The specs say it needs 15 amps but do you oversize the circuits 20% for minisplits with like a 20 amp breaker and 12 gauge wire?

 

[Tegbert]

I’ve been looking at adding some to my house too. I’m Leary of what some people say that they can heat/cool a large area with one head unit. I have even been told that by most installers that we wouldn’t notice much heating or cooling down to our bedrooms.

Most of the ones I have seen are on the verge of 12 gauge wire size so I assume 10 would be the way to go. But that was for 3-4 ton units. Also the ones I have looked at are only 3 wire. Two hots and and a ground. I’m not sure why the neutral is not needed.

Also they do have ceiling cassette ones if your roof trusses are 22” plus on center. That way you could put it centrally in the room and not have a box on the wall.

Not much help on the load calculation as I’m trying to figure out the same thing myself.


Lopi Rockport
Blaze King Ashford 25

 

[Highbeam]

I’ve been looking at adding some to my house too. I’m Leary of what some people say that they can heat/cool a large area with one head unit. I have even been told that by most installers that we wouldn’t notice much heating or cooling down to our bedrooms.

Most of the ones I have seen are on the verge of 12 gauge wire size so I assume 10 would be the way to go. But that was for 3-4 ton units. Also the ones I have looked at are only 3 wire. Two hots and and a ground. I’m not sure why the neutral is not needed.

Also they do have ceiling cassette ones if your roof trusses are 22” plus on center. That way you could put it centrally in the room and not have a box on the wall.

Not much help on the load calculation as I’m trying to figure out the same thing myself.


Lopi Rockport
Blaze King Ashford 25

Thanks Teg.

If my stove can heat the whole home from the stove room then I figure putting the minisplit head in the stove room would do the same thing. We are quite happy with the slight, 5-10 degree at most, variation in temperature from stove room to bedroom. HVAC nerds will say that this is "low" comfort but I love it.

If I'm running a new wire to that existing breaker I may as well use 10/3 and just not use the neutral at the disconnect. Perhaps a future device will want that neutral. I could also underbreaker the 10 gauge at 20 if that is what the equipment calls out.

The ceiling cassettes are also pretty ugly, even worse than the wall units in that they resemble an RV air conditioner and the wife doesn't want to live in a trailer! Those cassettes also usually have a condensate pump built in and they carry a large efficiency penalty.

These things are several thousand dollars. 2-3 for the unit and then who knows how much for install. I hate hiring people but this skillset is very unique.

 

[Tegbert]

I hear you about the install prices. I have had three quotes for 3 zones at about 13-14,000. I had another quote for 5 zones and just under 15,000 but that in my opinion is too much for my house.




Lopi Rockport
Blaze King Ashford 25

 

[Highbeam]

I hear you about the install prices. I have had three quotes for 3 zones at about 13-14,000. I had another quote for 5 zones and just under 15,000 but that in my opinion is too much for my house.




Lopi Rockport
Blaze King Ashford 25

Whoa, that's high. A single zone, single head unit should be much cheaper. If not, well, that will pay for a lot of resistance heating!

 

[SpaceBus]

I have resistance heaters and I am planning on getting one or two mini splits. The house came with 70's Merkel electric resistance baseboard heaters, but they are very expensive to run. They work very well, but power is too expensive here. There have been times when we need to leave for an extended period and can't run the stove, this means baseboards are on. Having AC sounds nice too, but I doubt we will ever need it. I agree with you on how they look, but most efficient things don't look nice, in the traditional sense anyway.

My stay in Afghanistan was heated exclusively by cheap Chinese knock off mini splits called Chigos. These worked extremely well, except for mine which didn't defrost. I'm not sure if any did, but it would wake me up in the middle of the night when the fan blades hit the ice. Despite having to chisel out the ice occasionally, I stayed warm. Temps were regularly single digits f. I am a believer.

 

[Tegbert]

Whoa, that's high. A single zone, single head unit should be much cheaper. If not, well, that will pay for a lot of resistance heating!

Should be much cheaper hopefully. But that is why I probably will be doing it all myself I can’t see spending 15k on something I won’t see any savings by installing it as we heat with wood like you so it would be used to heat while we are gone for long periods of time or when I’m lazy and don’t want a fire so my electric bill will be higher. It might be cheaper in the summer as we usually run two to three portable AC units though.


Lopi Rockport
Blaze King Ashford 25

 

[Highbeam]

Our power in this area is still right near 10 cents per KWH. So last night it was costing me 22.5 cents an hour to heat the place. Say 6$ per day. With a 144$ dollar wall heater that requires no maintenance. Dang it.

I'm going to try heating the place again tonight with just electric resistance heat to verify the numbers. Seems too low.

 

[SpaceBus]

Our power in this area is still right near 10 cents per KWH. So last night it was costing me 22.5 cents an hour to heat the place. Say 6$ per day. With a 144$ dollar wall heater that requires no maintenance. Dang it.

I'm going to try heating the place again tonight with just electric resistance heat to verify the numbers. Seems too low.

In my case it's the power company that is the issue. The service/delivery fees are as much as my power usage fees.

 

[Highbeam]

In my case it's the power company that is the issue. The service/delivery fees are as much as my power usage fees.

Our 10 cents is all in. Total bill divided by kwh used. I have heard of folks paying three times as much and at that rate there is more money to invest in these ultra high efficiency devices. Your payback period falls quickly! Also, solar even becomes a reasonable investment.

 

[SpaceBus]

Our 10 cents is all in. Total bill divided by kwh used. I have heard of folks paying three times as much and at that rate there is more money to invest in these ultra high efficiency devices. Your payback period falls quickly! Also, solar even becomes a reasonable investment.

I very much so would like solar, but other things come first.

 

[Brian26]

I am about to install one myself. After doing a ton of research they really are not hard to install at all. All you really need for specialized tools is a vacuum pump and micron gauge. The actual pipe connections is just 4 flare fittings. The condenser is precharged with the exact amount of refrigerant for up to 15 ft on lineset. These are installed by the millions all over the world by simply pulling a vacuum and opening the valve and letting refrigerant flow.

From my research almost all of the units are made by Gree with whatever brand sticker on them. Pioneer, Senville, blueridge, mr cool, etc. They all have pretty much the exact same manuals, remotes, etc. Gree is the largest air conditioner manufacturer in the world. Yeah its made in China but so are the other name brand units.

I ended up going with the Pioneer unit for $800 delivered to my house with everything included to install it. Its a cold weather/hyper heat model and provides full heat output to 5 degrees. It cuts out at -13 and Its certified by the American AHRI rating organization so they actually tested in the lab. From my research the Pioneer units have the best warranty and reviews online. Its the #1 seller on Amazon. I had to wait a month just to order it as the company that distributes them in Miami said they were selling them like crazy and waiting for more to arrive by ship.

If you have an HVAC company come out your looking at $4-5K for a Mitsubishi or Fujitsu. Yes they are the best and you get 12 year warranties but for $800 I can buy 5 Pioneers.

 

[Brian26]

Our 10 cents is all in. Total bill divided by kwh used. I have heard of folks paying three times as much and at that rate there is more money to invest in these ultra high efficiency devices. Your payback period falls quickly! Also, solar even becomes a reasonable investment.

According to the EIA Washington has some of the cheapest prices at 9.68 cents a kwh. I have heard its from all that hydro power there? Its way cheaper than even all the coal states like Wyoming.

https://www.eia.gov/electricity/monthly/epm_table_grapher.php?t=epmt_5_6_a

I installed solar 2 years ago but the electricity here in CT was almost 3 times that last I checked with all the fees and stuff. Solar was a no brainier here with those prices. Actually I just checked in its right behind Alaska at the highest in the US with Hawaii being number one.

My neighbor converted from electric heat to Mitsubishi mini splits and literally saved like a few thousand in the first year he said. He said his father converted in the 70s when it was cheaper to run electric heat. Some of the newer Fujitsu units have Coeffecient of performance near 4.5 now. Meaning they are 450% more efficient than regular electric heat. They are putting out an incredible amount of heat with very little power used. Some of them have cooling ratings of 33 seer now. I believe window ac's are around 8 seer so they use about 4 times less power cooling as well.

 

[Highbeam]

According to the EIA Washington has some of the cheapest prices at 9.68 cents a kwh. I have heard its from all that hydro power there? Its way cheaper than even all the coal states like Wyoming.

https://www.eia.gov/electricity/monthly/epm_table_grapher.php?t=epmt_5_6_a

I installed solar 2 years ago but the electricity here in CT was almost 3 times that last I checked with all the fees and stuff. Solar was a no brainier here with those prices. Actually I just checked in its right behind Alaska at the highest in the US with Hawaii being number one.

My neighbor converted from electric heat to Mitsubishi mini splits and literally saved like a few thousand in the first year he said. He said his father converted in the 70s when it was cheaper to run electric heat. Some of the newer Fujitsu units have Coeffecient of performance near 4.5 now. Meaning they are 450% more efficient than regular electric heat. They are putting out an incredible amount of heat with very little power used. Some of them have cooling ratings of 33 seer now. I believe window ac's are around 8 seer so they use about 4 times less power cooling as well.

I was surprised to see that 38% of my power is from coal. Our western Washington power is double to triple the cost of those eastern Washington cities near the power production dams. It’s basically free!

The cop of 4 means you get 3 for free. Electric resistance has a cop of 1. Pretty great but as a backup to wood heat or even using it half time with this cheap power I would expect decades to recover the cost of the equipment.

 

[Highbeam]

Another night in the 20s. I logged 55 additional kwhs over 24 hours by running resistance heat instead of wood heat. That again checks out to under 8000 btu per hour! I guess my insulation is pretty good when keeping the house just under 70. So 5.50$ in extra energy costs per day of electric resistance heat which is not as high as I would have thought.

If the minisplit cost 5000$ to install and cuts my resistance heat consumption by 66% (assuming a COP of 3), then I would only have paid 1.82$ so a savings of 3.68$ per day of use. It would take 1,358 winter days of use to cover the installation cost. If I was a non-woodburner and needed to heat on average 180 days per year then the thing would have a 7.5 year break even point. That's not bad if wood heat was flat out banned forever. The equipment should last 10 years. I made an assumption above of 180 days of heat but we really need less heat for a longer time in the shoulder seasons. I also believe that the COP of 3 is rather optimistic when it is below freezing but pretty close on average.

That last 2.5 years for free only adds up to a reward of 662 bucks. Will I even live here for 10 years? Will it even last for 10 years? Will there be a better technology in 10 years?

Since I do heat with wood. The only benefit is the 7 days a year or so that burning is banned where the savings would be 25.76$ per year. It would take 194 years to break even.

I am not going to install the minisplit. They are just too expensive to make financial sense in my situation due to small heating load and cheap power. Resistance heat for the win!

 

[begreen]

Good economic analysis. There are times when a mini-split makes sense for some and times when it doesn't. If one wanted AC too, then it would start to make a bit more sense perhaps. For us the decision was easier as we were replacing a god-awful expensive propane system. Unfortunately mini-splits and inverter compressor systems were not available locally at that time so we went for a high-end 2 stage central hvac instead. No regrets. The only thing we've done in 12 yrs is replace the filters and the operating cost is peanuts, less that the cost of wood and a lot cleaner.

 

[SpaceBus]

Another night in the 20s. I logged 55 additional kwhs over 24 hours by running resistance heat instead of wood heat. That again checks out to under 8000 btu per hour! I guess my insulation is pretty good when keeping the house just under 70. So 5.50$ in extra energy costs per day of electric resistance heat which is not as high as I would have thought.

If the minisplit cost 5000$ to install and cuts my resistance heat consumption by 66% (assuming a COP of 3), then I would only have paid 1.82$ so a savings of 3.68$ per day of use. It would take 1,358 winter days of use to cover the installation cost. If I was a non-woodburner and needed to heat on average 180 days per year then the thing would have a 7.5 year break even point. That's not bad if wood heat was flat out banned forever. The equipment should last 10 years. I made an assumption above of 180 days of heat but we really need less heat for a longer time in the shoulder seasons. I also believe that the COP of 3 is rather optimistic when it is below freezing but pretty close on average.

That last 2.5 years for free only adds up to a reward of 662 bucks. Will I even live here for 10 years? Will it even last for 10 years? Will there be a better technology in 10 years?

Since I do heat with wood. The only benefit is the 7 days a year or so that burning is banned where the savings would be 25.76$ per year. It would take 194 years to break even.

I am not going to install the minisplit. They are just too expensive to make financial sense in my situation due to small heating load and cheap power. Resistance heat for the win!

I don't blame you, it's radiant heat. Resistance heaters work well. We bought our house to retire in, so it makes more sense for us. Our state also offers a rebate on mini splits.

 

[peakbagger]

My installed (DIY) cost for a 12,000 Btu unit was around $2,700. The non economic paybacks were more important; the ability to skip running my boiler for about 4 months a year during shoulder seasons and the ability to head out for an extended period when my storage runs out during much of the heating season. Plus I get some AC for free.

 

[Highbeam]

Good economic analysis. There are times when a mini-split makes sense for some and times when it doesn't. If you wanted AC too, then it would start to make a bit more sense perhaps. For us the decision was easier as we were replacing a god-awful expensive propane system. Unfortunately mini-splits and inverter compressor systems were not available locally at that time so we went for a high-end 2 stage central hvac instead. No regrets. The only thing we've done in 12 yrs is replace the filters and the operating cost is peanuts, less that the cost of wood and a lot cleaner.

I believe that a reasonably efficient central HVAC system adds value to the home so if I had ducts then I would be installing some type of central furnace system but I do not believe that these minisplit systems have gained enough acceptance to be a value adder to a home sale over baseboard heat. That is, unless you are an HVAC nerd and the equipment is top notch.

I'm also not convinced that your 2 stage system was a bad way to go. The increase in efficiency for variable compressors and evaporators would likely not have been enough to pay for the added equipment costs over its life given your wood heat supplement and our cheap electricity. There is a lot to be said for simple, cheap, low seer, single stage heat pumps. Soon they will steal enough technology to be able to make full output in cold temperatures without the strip heat.

 

[Highbeam]

My installed (DIY) cost for a 12,000 Btu unit was around $2,700. The non economic paybacks were more important; the ability to skip running my boiler for about 4 months a year during shoulder seasons and the ability to head out for an extended period when my storage runs out during much of the heating season. Plus I get some AC for free.

Thanks Peak, the self install saved you a ton! Installing cheap baseboard electric heaters (or if they are existing) also would have allowed you to head out for an extended period too.

Luckily we don't need AC. If it was a need in this area, there would have already been ducts and a conventional split system would be the logical way to go.

With solar, and high cost electricity, the economics might be a bit different.

 

[Dobish]

we are looking at some options for our house too, and I was contemplating a mini split for the upstairs. Right now the stove does most of the wood, but in the summer it is brutal without AC (which we do not have). Our basement stays pretty cool in the summer, and without the stove is freezing in the winter. We didn't burn for a couple of days and our basement stayed around 56º. I could tell that our furnace was kicking in, but it wasn't bringing the temp up down there.

We are putting in radiant heat cove heaters in our new garage build, and I have been in a few places that have them. the heat just feels really nice in there. We were thinking about adding a few to our bedrooms/downstairs living room with a separate thermostat at some point. I think we are going to wait and see what the electric bill comes in at.

 

[begreen]

I believe that a reasonably efficient central HVAC system adds value to the home so if I had ducts then I would be installing some type of central furnace system but I do not believe that these minisplit systems have gained enough acceptance to be a value adder to a home sale over baseboard heat. That is, unless you are an HVAC nerd and the equipment is top notch.

I'm also not convinced that your 2 stage system was a bad way to go. The increase in efficiency for variable compressors and evaporators would likely not have been enough to pay for the added equipment costs over its life given your wood heat supplement and our cheap electricity. There is a lot to be said for simple, cheap, low seer, single stage heat pumps. Soon they will steal enough technology to be able to make full output in cold temperatures without the strip heat.

When we bought our system there were no single-stage system with good HSPF. I haven't checked to see if this has changed, but I suspect not. Usually the best performers are the premium systems. It's not all about payback. There are other benefits to multistage units. One major one is quietness, another is reduced electrical consumption. We're in it for the long haul. Like our solar setup, payback periods of 6+ yrs are ok. With a $3000+ wood & propane bill (and climbing) compared to now the heating system upgrade paid for itself pretty quickly.

 

[Highbeam]

That’s key, you had a 3000$ heating bill. That large (for this area) bill provides the potential for savings. Savings that pay for improvements within a reasonable period of time.

 

[begreen]

Yes, propane is ridiculously expensive in our area. Captive market. It's the worst fuel for heating here. And our house is old with too much glazing. Crazy as this may seem, the cost of propane went up quite a bit more after we got the new system! We don't miss it at all. Our annual heating bills including wood purchased dropped down to the $500-700 range by the next winter depending on how much wood I scrounged up vs buying.

 

[woodgeek]

I've done similar BTU load tests when my HP compressor failed 4 years ago and I was running resistance backup.

I am sure your BTU figures are within 10%. A few separate minor factors....
1. Wind increases BTU load in a highly non-linear way.
2. BTU loads from stack effect air leakage are quadratic in Delta-T, not linear.
3. BTU loads on unusually cold nights are lower than expected from a linear model Delta T due to thermal buffering by the ground on the foundation.
If your wind was low, 2 and 3 probably canceled each other out.

Sounds like a minisplit is a no-brainer in terms of functionality (assuming you want an AC). Its more about comfort than $$, and then it s a personal decision, not an economic one.

As for the ugly....I suspect that after a few weeks you will cease to notice it at all.