Ductless mini-split vs stoves

[derbydude]

I need to add an alternate heat source to oil. When I look at Heating fuel price calculators, mini-splits run even with pellets, at 20c per kwh (electric) vs 250$ for pellets.
But one thing I see, BTUs for most mini-splits are barely 10-15K BTU, yet they claim to heat an area of 600sft. How can they keep the room(s) warm when even the smallest pellet stoves produce 20-30,000 BTUs and they claim to heat rooms of same size?
what am I missing? Is it marketing hype from mini-splits?

 

[peirhead]

The difference you are seeing is probably related to delivered heat efficiency...the heap pumps pretty well deliver into the room what they claim, whereas the stoves you are lucky to get 75 - 80% efficiency.
I suggest you work out how many BTU per hour you need to keep your house at the temp where you want it then work backwards to determine the better source. If I was buying again I'd probably go heat pump rather than pellets, but my power is around 13 cents / KWh

 

[woodgeek]

I agree with your BTU cost calculations. Assuming a COP of 2.75 for the mini, $0.20/kWh works out to $20 per million BTU delivered, $250 pellets are about the same. Oil at $3.50 is about 50% higher, at $30 / MMBTU. None are exactly what I would consider cheap.

The $0.20/kWh power in CT is really a bear. I thought you guys were 'only' at $0.18. Have you checked to see if 'electric heating' customers get a (perhaps small) break on price? Is $0.20 your real marginal rate, or are you factoring in a fixed monthly service into a low usage?? Any rebates from the utility for mini install??

Keep in mind that some minis can put out more than the rated BTU/h at higher outdoor temps. If you research, you should be able to find a table of BTU output versus outdoor temp; they vary a lot even for the same nominal output across make and model.. My (non mini) HP puts out >50 kBTU at 40°F outside, half that at 10°F. The COP will also vary. The COP might be 3 or above in mild weather, closer to 2 during very cold weather, esp if snowy.

I would factor in that the mini would be low/zero maintenance, unlike having to load/clean the pellet stove, and have pro service done on the oil boiler. You will turn the mini on, and it will just do its thing for years, and you get cheap and quiet AC too.

 

[derbydude]

I agree with your BTU cost calculations. Assuming a COP of 2.75 for the mini, $0.20/kWh works out to $20 per million BTU delivered, $250 pellets are about the same. Oil at $3.50 is about 50% higher, at $30 / MMBTU. None are exactly what I would consider cheap.

The $0.20/kWh power in CT is really a bear. I thought you guys were 'only' at $0.18. Have you checked to see if 'electric heating' customers get a (perhaps small) break on price? Is $0.20 your real marginal rate, or are you factoring in a fixed monthly service into a low usage?? Any rebates from the utility for mini install??

Keep in mind that some minis can put out more than the rated BTU/h at higher outdoor temps. If you research, you should be able to find a table of BTU output versus outdoor temp; they vary a lot even for the same nominal output across make and model.. My (non mini) HP puts out >50 kBTU at 40°F outside, half that at 10°F. The COP will also vary. The COP might be 3 or above in mild weather, closer to 2 during very cold weather, esp if snowy.

I would factor in that the mini would be low/zero maintenance, unlike having to load/clean the pellet stove, and have pro service done on the oil boiler. You will turn the mini on, and it will just do its thing for years, and you get cheap and quiet AC too.

Its about 0.18+ or 0.19 approx - I rounded to 0.20 - it wont be too long before we get there. We jumped from 0.16 I believe just 2 yrs ago.
I can get slightly lower rates by shopping around. I dont have a fixed monthly service or rate - not sure what that is.
There is a 500$ rebate for mini-splits.
Thats funny about the BTU ouptut vs outside temp - its exactly the opposite of what I would want.
Im still debating going to wood - the daily work puts me off.

 

[Seasoned Oak]

20c a Kwh .Thats pretty high. IM spoiled at about 10c a Kwh.

 

[woodgeek]

I dont have a fixed monthly service or rate - not sure what that is.
There is a 500$ rebate for mini-splits.
Thats funny about the BTU ouptut vs outside temp - its exactly the opposite of what I would want.
Im still debating going to wood - the daily work puts me off.

I pay $7/mo + 12.4 cents/kWh. The $7 is fixed wrt to usage.

Yeah, the declining output thing makes folks mad. Ultimately, the pressure of the refrigerant declines with temperature, so less energy flows at low outdoor temps. Minis can compensate this by throttling up the variable speed compressor as the temp falls, to make more BTus as the temp falls, until they hit the wall, and then they start to drop off too. Trying to describe that with a nominal BTU size makes for mistakes. You want to compare outputs at your typical January temps, sometimes obtainable from the manufacturer. Two units with the same nominal output can vary a lot at low temp.

 

[BrotherBart]

I dont have a fixed monthly service or rate - not sure what that is.

If you are with CL&P you have a sixteen dollar a month fixed "distribution customer service charge" that you are gonna get even if you don't use one KWH. Or if you buy the power from someone else but it is delivered on their poles. It is in their tariff.

 

[Seasoned Oak]

Im still debating going to wood - the daily work puts me off.

It makes a great backup heat source. No daily work required. I also like the beauty of a wood fire as much as the heat factor. You just cant get that from anything else.I had a gas fireplace,its a poor substitute.