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THINKFR33LY t1_j5hamxw wrote

Heat pump won't be cheaper than oil unless the temps stay in the 40s+, and that's with a brand new heat pump. Electricity is north of 33c/KwH... crushes the value of a heat pump.

I switched my cut over temp to 45f. Anything lower than that and I'm using oil, which right now is a big north of $4/gallon.

As others have said... solar and insulation. Not much else you can do. I did switch to Constellation as my provider, which helps.

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MajorProblem50 t1_j5i7nqe wrote

Are you sure you aren't talking about heat pumps with inverters? These days they're fully efficient down to -15F, at least mine is.

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THINKFR33LY t1_j5j8iio wrote

They're not fully efficient down to -15. They can produce heat all the at that temp, but they're going to use much more power than at 30f for example.

I have the newest bosch heat pumps. With oil at $4 and electrical at north of 45c with delivery fees, a heat pump with a cop of 3 or so is more expensive than oil with sub freezing temps outside.

The most efficient Mitsubishi mini split might extend that down to the 20s, but def not -15.

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techorules t1_j5kvj3v wrote

Maybe not "Fully" efficient but my Mitsu Hyper Heat Pump has a COP of 1.7 at -15 F. So even at those temperatures it can beat out other fuel types depending on prices. For instance for a propane customer even with a fairly high electric rate per kWh would still beat out propane. Probably oil too.

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langjie t1_j5l14ap wrote

3412 btu/kwh x 1.7 COP = 5,800 btus.

oil at $4 /gal: 138,700 btus * 80% boiler efficiency = 110,960 btu's (19.1 kwh of heat pump). electricity needs to be at 21 cents/kwh to be equal to $4 oil if outside is @ -15°F

propane at $2.5 /gal: 91,700 btus * 80% boiler efficiency = 73,360 btu's (12.6 kwh of heat pump). electricity needs to be at 20 cents /kwh to be equal to $2.50 propane if outside is -15°F

all depends on the rate but also it's typically not that cold out so the math changes with increased efficiency

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techorules t1_j5l3wyu wrote

Cool. Yeah my electricity is way below those figures..... Also propane averages in Mass are way way higher than $2.5. My last delivery (which I am hoping I literally my last ever) was over $4. And with climate change sadly -15F is pretty rare indeed.

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oceanblake t1_j5ibkkm wrote

What he says it wont be cheaper. Analogy to this may be electric car would not save that much money in winter compared to efficient gas/hybrid when electricity is this high we have now

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mountainwocky t1_j5js2ok wrote

I actually used the efficiency specs for our heat pump to calculate cost to operate at various temperatures and was surprised to find that operating our heat pump is actually less expensive than running our pellet stove.

Actual use correlated well with the calculated savings to use the heat pump too.

I’ll switch over to the pellet stove only once temps fall to below 20F. It’s nice because where I’d buy and burn 3 tons of pellets in a winter, now I only go through a ton. Newer heat pumps are even more efficient than my system and can show saving even in subzero temperatures.

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SeaworthinessLeft88 t1_j5l6wq1 wrote

It really depends. I’m fortunate to have a community aggregate program, and after doing the actual math, oil needs to be below $3/gal for it to be cheaper than running the heat pump on my current electricity rates. Right now, it’s going for roughly $4/gal, so it’s not even close.

My heat pump isn’t new, but it’s not old either (installed in 2016). It’s a power hog under ~20F, but I think it’s still cheaper than burning oil at these rates.

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