4 ms·
The problem is in "extract the energy". If your refrigerant can reach -20 in your system, and it's 30C outside, then your refrigerant is exchanging 50C of ener
by mabbo 5y ago
The problem is in "extract the energy".
If your refrigerant can reach -20 in your system, and it's 30C outside, then your refrigerant is exchanging 50C of energy per cycle. But if it's -15C outside, the best you can achieve is 5C of energy exchanged per cycle. And at -20C outside, you can't exchange heat at all.
That's a bit hand-wavey and not exact units, but I think it accurately describes the problem.
What the above poster is saying is that as temperatures drop, the system gets less and less efficient. For some environments, it may become cheaper to use resistive electric instead.
The 'Technology Connections' channel did a series of videos about heat pumps that are fascinating and I highly recommend: https://www.youtube.com/channel/UCy0tKL1T7wFoYcxCe0xjN6Q https://www.youtube.com/channel/UCy0tKL1T7wFoYcxCe0xjN6Q.
- BizarroLand 5y agoThat is why they are hybrid heat pump water heaters. When the air is insufficiently warm to heat your water, the heat pump can switch back to traditional electric heater rods. They do run about 2x the price of a non-hybrid (My local hardware store has an 80 gallon hybrid for $2250 vs $1080 for the non-hybrid) but my power company is offering a $500 instant rebate as well as the county offering a $300 rebate, so in my case, it's a few hundred extra bucks for a few hundred dollar annual reduction in my power bill.
- giantg2 5y agoWow 80 gallons is huge. I can see it making sense at that volume. I find the benefits to be marginal when using an average 40 gallon or less and only using it for 1-2 people. The use of water conserving fixtures further reduces the benefits for smaller tanks with fewer people (not sure they even make them smaller than 40 with the heat pump). With the exception being for people in hot climates with the tank in the garage or similar space.