Alternative heat source, minisplits for real?

twd000 · Jan 23, 2019

unless I'm missing something here, I don't see the savings for my fuel choices

ignoring distribution and duct losses (which would be the same for central heat pump and furnace)

propane: $2.15/gal / 92,000 BTU * 1,000,000 MBTU = $23.37/MBTU
heat pump w/ avg 2 COP: $0.20/kWh / 3,412 BTU / 2 COP * 1,000,000 MBTU = $29.31, or 25% MORE than propane.
If I optimistically assume 3 COP, it's only $19.54, or 15% savings over propane. Seems like it would take a long time to payback new heat pump equipment at a COP of 3, and at a more realistic COP of 2, it actually would cost me more.

maple1 · Jan 23, 2019

There is also combustion (in)efficiency with LP that should be factored in.

I don't know what LP prices are around here but I think around 0.90/litre.

Electricity used is 0.15/kwh.

My heat pumps spec at 3.8 & 4.0 COP.

Assuming a COP of 3 and ignoring LP inefficiency, I get 36.22 for LP & 14.65 for splits.

Wide variations place to place of course. And COP would vary with outside temp - we're fairly moderate but also very varying. Was -16c here this morning.

Our fuel oil costs I think would be similar to LP.

twd000 · Jan 23, 2019

maple1 said:
There is also combustion (in)efficiency with LP that should be factored in.

I don't know what LP prices are around here but I think around 0.90/litre.

Electricity used is 0.15/kwh.

My heat pumps spec at 3.8 & 4.0 COP.

Assuming a COP of 3 and ignoring LP inefficiency, I get 36.22 for LP & 14.65 for splits.

Wide variations place to place of course. And COP would vary with outside temp - we're fairly moderate but also very varying. Was -16c here this morning.

Our fuel oil costs I think would be similar to LP.

good point on the furnace efficiency - the label on mine claims 92.5 AFUE, so my propane cost is really $25.26/MBTU
Your propane is even more expensive than ours

Having a hard time finding real world COP - are you really averaging COP 3 across an entire winter? I have seen #'s from 2-4 COP which makes a huge difference

maple1 · Jan 23, 2019

twd000 said:
good point on the furnace efficiency - the label on mine claims 92.5 AFUE, so my propane cost is really $25.26/MBTU
Your propane is even more expensive than ours

Having a hard time finding real world COP - are you really averaging COP 3 across an entire winter? I have seen #'s from 2-4 COP which makes a huge difference

I just kind of pulled 3 out of the air. Rated at 4. But I really have no idea what it would be averaged over a winter.

Brian26 · Jan 24, 2019

Got to test the unit out in some milder weather. Was in the 40s yesterday and is currently 50 out. Heat output really goes way up in these temps. What I didn't realize is it is actually rated at putting out around 17k btus when its above 44 degrees outside. Pretty impressive for a 110v 12k unit.

Brian26 · Feb 1, 2019

Been doing extensive testing and monitoring since my install and these things are incredible at pumping out heat in very cold weather. I have sensors monitoring return and supply air and my efergy monitoring its power consumption.

This unit can prettty much always maintain a 30-40 degree temp rise between the return and supply air (delta t). Here is a chart from overnight when I fired it up this morning. Intake temp was 64 and it was putting out 105 degree duct air within minutes. Outside temp was 9 degrees.

Screenshot_20190201-064858_My AcuRite.jpg

SpaceBus · Feb 1, 2019

Did it feel like 64? Between loads while we sleep (or if I don't wake up to load the stove) the house gets down to 62-64 depending how long it has been. The electric baseboard heaters take over if it gets down to 62. While I'm awake or if I wake up to load the stove it never goes below 68 and usually it's above 72 inside. Our house is small, so I can raise the first floor temp close to 3 degrees an hour. Even faster if the sun is out.

I have the thermostat set so low because the baseboard heat is expensive and I can usually reload before the house gets cold. It would be nice to have cheap heat that feels warm. My wife like really has a thing about heat pump heat, she just stays cold. Sometimes she doesn't even warm by the stove!

Brian26 · Feb 1, 2019

SpaceBus said:
Did it feel like 64? Between loads while we sleep (or if I don't wake up to load the stove) the house gets down to 62-64 depending how long it has been. The electric baseboard heaters take over if it gets down to 62. While I'm awake or if I wake up to load the stove it never goes below 68 and usually it's above 72 inside. Our house is small, so I can raise the first floor temp close to 3 degrees an hour. Even faster if the sun is out.

I have the thermostat set so low because the baseboard heat is expensive and I can usually reload before the house gets cold. It would be nice to have cheap heat that feels warm. My wife like really has a thing about heat pump heat, she just stays cold. Sometimes she doesn't even warm by the stove!

I am still fine tuning the ideal setpoints. I have been letting the oil burner carry most of the load as its been pretty cold here. I am on the CT shoreline so these single digit temps are rare. When its in the 30s and 40s the oil burner is off. I have saved a ton on oil since I installed it. Looking forward to seeing the data when its in the high 50s next week.

semipro · Feb 1, 2019

SpaceBus said:
My wife like really has a thing about heat pump heat, she just stays cold.

In many cases, this is due to evaporative cooling on skin from too high a fan speed in heating mode. A variable speed ECM motor in the air handler can be retrofitted to address this issue. You can also just rewire the air handler fan to run on its lowest speed.

SpaceBus · Feb 1, 2019

Brian26 said:
I am still fine tuning the ideal setpoints. I have been letting the oil burner carry most of the load as its been pretty cold here. I am on the CT shoreline so these single digit temps are rare. When its in the 30s and 40s the oil burner is off. I have saved a ton on oil since I installed it. Looking forward to seeing the data when its in the high 50s next week.

We are on the coast, but the bays and harbors shield is from the worst of the weather. The wind will still take some heat from the house. Still, the stove will be doing most of the heating for our house, the mini splits would be back up, with the electric baseboards being back up for the mini splits.

SpaceBus · Feb 1, 2019

semipro said:
In many cases, this is due to evaporative cooling on skin from too high a fan speed in heating mode. A variable speed ECM motor in the air handler can be retrofitted to address this issue. You can also just rewire the air handler fan to run on its lowest speed.

Well, we don't have an air handler at all on our new (built in 77) house. That at first made her very nervous, but she has warmed up to the electric baseboard heaters. I wish electrical service weren't so expensive here, but we knew there would be sacrifices to living in such a remote area. On a sunny day like today I have to use very little firewood, if any at all while the sun is up.

DBoon · Feb 2, 2019

SpaceBus said:
It would be nice to have cheap heat that feels warm. My wife like really has a thing about heat pump heat, she just stays cold.

I can tell you that these mini-splits deliver warm heat. I too was once skeptical having lived with crappy ducted units that just pushed out cool air until the electric resistance strips kicked on. The mini-splits are way different than that.

peakbagger · Feb 2, 2019

I differ a bit on my perception of heat from my minisplit compared to baseboards. My boiler and storage is in the basement and it keeps the floor warm. I can set my thermostat several degrees lower when the basement is warm. I tend to take days off from burning in the winter and use the minisplit. Its quite noticeable that I need to run the minisplit at a higher temp to match the comfort level that I get away with burning wood.

When I worked in offices there was always a battle over thermostats with women usually complaining they were too cold. We sometime would buy low wattage floor mat heaters for the ladies. It cut way down on complaints.

SpaceBus · Feb 2, 2019

peakbagger said:
I differ a bit on my perception of heat from my minisplit compared to baseboards. My boiler and storage is in the basement and it keeps the floor warm. I can set my thermostat several degrees lower when the basement is warm. I tend to take days off from burning in the winter and use the minisplit. Its quite noticeable that I need to run the minisplit at a higher temp to match the comfort level that I get away with burning wood.

When I worked in offices there was always a battle over thermostats with women usually complaining they were too cold. We sometime would buy low wattage floor mat heaters for the ladies. It cut way down on complaints.

This is exactly what I needed to hear. While we do not have hot water baseboard heaters, ours are electric, my wife still prefers them over forced air now that she trusts them to not burn the house down. This makes me less in a hurry to change them, she is leery of a DIY install and getting a pro to do it is crazy expensive.

maple1 · Feb 2, 2019

One of our units is a 'floor mount'. Still attached to the wall but sits on the floor. It can send heat out both low along the floor and from the top, into the middle of the room. I think it improves the 'warm but feels cool' thing.

SpaceBus · Feb 2, 2019

maple1 said:
One of our units is a 'floor mount'. Still attached to the wall but sits on the floor. It can send heat out both low along the floor and from the top, into the middle of the room. I think it improves the 'warm but feels cool' thing.

The low mount makes a lot of sense. I don't think we could find a practical location for one in our house, unfortunately. Perhaps this is where the professional install makes more sense.

Ashful · Feb 2, 2019

Went out to my shop this morning, with dual Mitsubishi minisplits, and it was 45F in there. Thermostats were set to 55, but system wasn’t running. Bumped them both up to 70, and they started pumping heat straight away. Weird, but par for the course, with these units.

We’ve been hovering near zero for the last few days, but last night was a balmy 16F, and i think it even went up above freezing this afternoon.

Brian26 · Feb 3, 2019

SpaceBus said:
This is exactly what I needed to hear. While we do not have hot water baseboard heaters, ours are electric, my wife still prefers them over forced air now that she trusts them to not burn the house down. This makes me less in a hurry to change them, she is leery of a DIY install and getting a pro to do it is crazy expensive.

A mini split would save you a fortune over electric baseboard heaters. A good Mitsibushi or Fujitsu with a 12.5 HSPF would cost you almost 4 times less for a million BTU's.

Cost per million btu's.

Electric baseboard- $46.89
Mini Split- $12.80.

www.pacificpud.org/heatcalc.xls

SciGuy · Feb 3, 2019

twd000 said:
unless I'm missing something here, I don't see the savings for my fuel choices ignoring distribution and duct losses (which would be the same for central heat pump and furnace)
propane: $2.15/gal / 92,000 BTU * 1,000,000 MBTU = $23.37/MBTUheat pump w/ avg 2 COP: $0.20/kWh / 3,412 BTU / 2 COP * 1,000,000 MBTU = $29.31, or 25% MORE than propane.
If I optimistically assume 3 COP, it's only $19.54, or 15% savings over propane. Seems like it would take a long time to payback new heat pump equipment at a COP of 3, and at a more realistic COP of 2, it actually would cost me more.

Are you certain about your cost of propane? It looks way out of wack compared to current pricing here in Upstate NY.
When I Google propane prices in New Hampshire I find the following much less attractive value.

Hugh

twd000 · Feb 4, 2019

Wow I don't know anyone paying $3.17, unless they're heating their house with 20-lb BBQ tanks! I buy as part of a co-op and they set rates every spring based on usage. What are you paying in NY?

SciGuy · Feb 4, 2019

twd000 said:
Wow I don't know anyone paying $3.17, unless they're heating their house with 20-lb BBQ tanks! I buy as part of a co-op and they set rates every spring based on usage. What are you paying in NY?

IIRC it cost $2.90/gallon for a fill up in the middle of last winter and prices are running as high as $3.75/gallon this year in the north country. So if you called for a fill up today it would only run $2.15 or was that the summer time price?

twd000 · Feb 4, 2019

SciGuy said:
IIRC it cost $2.90/gallon for a fill up in the middle of last winter and prices are running as high as $3.75/gallon this year in the north country. So if you called for a fill up today it would only run $2.15 or was that the summer time price?

yes this was the pre-buy price - the co-op always sets rates after the heating season ends so it's cheaper. I'm not sure what I would pay in today's spot price with no contract, but I would guess closer to $2.50

Brian26 · Feb 4, 2019

twd000 said:
yes this was the pre-buy price - the co-op always sets rates after the heating season ends so it's cheaper. I'm not sure what I would pay in today's spot price with no contract, but I would guess closer to $2.50

The EIA has propane prices at $3.28 a gallon as of 01/28 in New Hampshire. Thats the average of what most are paying.

https://www.eia.gov/dnav/pet/PET_PRI_WFR_DCUS_SNH_W.htm

My heat pump with a hspf of 12 would still cost half to run using your $2.15 propane price.

Using the above fuel cost calculator and thr EIA for .16 kwh price in NH.

Per millions btus.

Mini split. 13.33
2.15 propane 26.16
Eia 3.29 average. 40.03

twd000 · Feb 4, 2019

Brian26 said:
The EIA has propane prices at $3.28 a gallon as of 01/28 in New Hampshire. Thats the average of what most are paying.

https://www.eia.gov/dnav/pet/PET_PRI_WFR_DCUS_SNH_W.htm

My heat pump with a hspf of 12 would still cost half to run using your $2.15 propane price.

Using the above fuel cost calculator and thr EIA for .16 kwh price in NH.

Per millions btus.

Mini split. 13.33
2.15 propane 26.16
Eia 3.29 average. 40.03

I don't know what to tell ya. I promise I'm not sleeping with my propane delivery guy!

Brian26 · Feb 4, 2019

twd000 said:
I don't know what to tell ya. I promise I'm not sleeping with my propane delivery guy! View attachment 240184

Looks like you pay a good price. I was just pointing out that a good mini split would cost you half even at $2.15 propane. The majority of people that pay the retail price of $3.29 would save almost 3 times the amount.

On a related note. I finally got to run my unit in some milder weather. Its in the 40's this morning and its pumping out 136 degree heat with a 71 return air temp. An impressive almost 70 degree temp rise across the evaporator!

Another added benefit of these mini splits is they don't dry out the air according to my sensor monitoring on the return and supply.

Screenshot_20190204-102525_My AcuRite.jpg

Alternative heat source, minisplits for real?

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