I live in a very cold part of the world where the temps can easily exceed your -20C for night times for several weeks at a time. And even as the daily high for a week stretch or two over a winter. And while I could have purchased a heat pump that would work to that low of a temperature, it would have cost over twice the price. Going from $5000US installed to over $10,000US for just the heat pump. And that included the rebate incentives.
My heat pump is set to set to cut out and switch to LP heat at -10C because it becomes cheaper to run an LP furnace at that point - cost of electricity = 6.5 cents per kilowatt hour vs $1.75US gallon LP. The loss of efficiency matters to my pocket book. And I chose my particular heat pump with my advice of my Daughter who has a PhD in ME and works as a research engineer for a non-profit studying HVAC systems and the efficiencies of the technology used in them. And she won’t install a heat pump in her house because for where she lives, they literally do not make financial sense. There is zero savings to be had with switching from natural gas heat to electric.
So installing a heat pump is not a universal no brainer. You still need to to the math to see if it pays.
I am also an engineer and used to have LP backup heat and the only way the LP is cheaper per BTU is if you rapidly deprecate the asset.
A gallon of propane has 91,000 BTU, and a kW of electricity has 3400 BTU. 91k/3.4k ~ 26kWh x 0.065 = $1.73 for electricity equivalent at 1.0 coefficient of performance. But your COP is likely around 2-3, so the heat pump will be at least 2x cheaper than the LP.
Critical_Insight@feddit.uk 11 months ago
Yeah obviously it’s a whole different game when you live in a place like that. That’s just quite rare usecase. The vast majority of people who keep repeating the “heatpumps don’t work in cold climates” lives in a climate much warmer than I do. Even mine struggles on the few really cold days we get few times a year but that’s fine because it gets the job done flawlessly for the remaining 350 days.
bluewing@lemm.ee 11 months ago
My issue with these arguments is the blanket statements that get made. Both arguments on this particular subject can both be true at the same time. And until you do the math for your specific situation, you can’t tell if it pays until you know the answer
Now, I believe it works out for you just as it does for me. But I had to the math to figure it out to know for sure. Most people who argue over this subject have never done the math.
Critical_Insight@feddit.uk 11 months ago
If your intention is to heat or cool air using as little electricity as possible, a basic split air conditioning unit is going to be more than adequate for 90% of people. If you live in Yakutia, then yeah you probably need to look into something else, but for the vast majority of people it’s going to be fine. A general recommendation doesn’t mean it’s the best choice for literally every single person.
bluewing@lemm.ee 11 months ago
But it very often catches many who simply take it as an irrefutable truth.
As I gave as an example, my one Daughter who is recognized by her peers as an expert in this field, and is all about improved efficiency and renewable energy, did the math and found that it doesn’t work for her. And it’s not because she lives in a terrible climate - it’s warmer and varies less than where I live by a noticeable amount. It’s because when you compare total costs, over the life span of a heat pump, she would end up paying extra to have one verses a simple natural gas furnace. It would be even sillier for my neighbor who is a logger. He uses 100% wood heat. Because he can literally harvest, process, and store enough firewood for several years in one afternoon. Anything else is far more expensive. But the math says it works for me.
You can’t make general statements about 90% of all people until everyone does the math. This is just one of the field studies my Daughter is doing. Trying to collect enough real time data on real homes and families and doing the math to help pinpoint locations where it makes sense and where it does not make sense at this time. It does not always workout like you and I might think it would.