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MajorProblem50 t1_j5i7nqe wrote

Reply to comment by THINKFR33LY in Monthly Electricity Bill Is Killing Me by haitiandev

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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