this post was submitted on 31 Jul 2023
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Are heat pumps goo for your wallet or the environment without also having solar panels?
Please don’t take this as me implying something. It’s a question I’ve had for awhile as I’m in a position where I could get a heat pump, but am unsure if it’s a good decision without solar and solace would be difficult for me because of how often my home is shaded.
Yes, because they move heat instead of creating it by burning stuff. This lets them be more than 100% efficient. You can expect something like 300% efficiency averaged over a year for air-sourced heat pumps in the US which are sized correctly for the house they're in. This makes them a net benefit, even on the current electrical grid.
People also often choose to add insulation when installing heat pumps, as this has the benefit of lowering overall system cost, which makes the situation even better.
It depends on how much of the grid's electricity is generated with fossil fuels I think. If the majority of the electricity is being generated with natural gas, a gas furnace can potentially use less gas to heat a home. But installing heat pumps also means that as more of the grid's electricity comes from renewable sources, there will be an immediate drop in the amount of carbon released into the atmosphere to heat homes.
They are -- the short answer is that installation is sometimes expensive because sometimes it's hard to connect it to someplace it can use to exchange the extra heat / cold, but once they're in, they're basically guaranteed to be more efficient than whatever else you're doing, since they have above 100% efficiency.
As usual, Technology Connections has a great video that goes in depth about it.
Did you... did you just claim over 100% efficiency? Physics has an issue with this. Also, I have something to tell you, a heat pump is just a reversible Air Conditioner.
Definitely better than a electric heater or a gas furnace, not some sort of miracle product.
Yes, they are typically calculated as having above 100% efficiency as they use the energy to move and concentrate heat instead of producing it like other heating systems. I agree that this is technically wrong, but it does make sense when looking at it in the above context of heating systems.
Yes, over 100% efficiency is exactly what I claimed. In winter, you'll get more BTUs of heat output from a heat pump than you had put in as BTUs of electricity input -- because instead of converting the electricity to heat, it's using the electricity to pull heat from the outside and put it in your house. Hence, it's a more energy-efficient way to do things than the laws of physics would allow for a device that directly converted electricity to heat. That's what it means to be a reversible air conditioner, yes.
IDK why me saying that is some kind of controversial statement -- it's simply a factual description of the product. There are scenarios and real-world constraints which may mean it's more or less sensible to install one, but over 100% efficiency is, exactly, the selling point of a heat pump.
Yes, he pumps do move more heat than the electricity that they consume. That's because they are a heat pump, not an energy conversion system like a motor.
No it doesn't - you're not creating heat, you're moving it. You can move more heat than the amount of energy you expend moving it. Hence the efficiency above 100%
It's a really bad piece of jargon, but is an internally consistent definition. They mean (heat entering building)/(work consumed) > 1
Which is a way if defining efficiency (energy out / energy in), just a really awful and misleading one.
In terms of % of carnot efficiency, the best heat pumps are about where stationary heat engines generally are, 40% or so.
Thank you! It seems to me to be like saying "LEDs are more than 100% efficient because we're applying the same metric of efficiency that we would for incandescent bulbs". They're two different methods of generating heat, why would you use the efficiency rule from one to judge the other?
The one I had installed easily uses half of the power to keep my house the same temperature as the old forced air electric heater did.
If your gas prices are heavily subsidized (most of the US) or your electricity prices are set to subsidize industrial users and line to pockets of monopolists (lots of the US and Europe) then it's roughly the same, maybe favouring gas by 10-50%.
If you are paying what either actually costs then the heat pump is better.
Yes, even if your local every supplier is burning coal the heat pump will bring more heat in your house that is you were burning the same amount of coal in your home.
When I installed new equipment, I installed a heat pump instead of an A/C as a future proofing move. The furnace I installed is 98% efficient the heat pump is a 9.7 HSPF unit. With the current prices of gas and electricity it will never be cheaper to run the heat pump. I knew that going in, but decided a dual fuel setup was worth a little additional cost in case fuel prices change or I install solar. That was before the current incentives, I'm not sure what they have done to the pricing. With the previous federal incentives and local incentives I only paid a few hundred dollars over a comparable A/C unit.
Yes...and no. It's complicated. I moved from one shitty rental to another, that had a heat pump and tbh when it's not one weather extreme or the other the answer is probably yes. The complicated part is in the rental. You see there are several holes in the home that allow daylight through and thus causes insulation issues. As a result my house heats up every day even with the heat pump running and the heat pump rarely shuts off even during the night (Texas). On the other hand the heat pump consumes roughly 50% the energy my old AC did and unlike my old AC also provides heat which in Texas is enough for 99.5% of the year....though this does mean I have a fairly consistent power bill as a result. The heat pump my rental has isn't very efficient (16 seer I think) and for a while was undercharged. If this house had solar of at least 3kw I think I could run the heat pump on pure solar and never use the grid...but it doesn't.
Again it's complicated, I actually love the heat pump...but it's in a shitty rental. If this were my house we'd probably be having a completely different discussion on performance. I think part of what should happen is the government subsidizing/rewarding landlords for fixing up inefficient homes with updates and for rewarding proper installation of things like heat pumps. I didn't mention this before but the heat pump was not properly installed either. It is mated to the previous A/C air handler and probably has a refrigerant leak as a result.
For what it's worth there's at least two other appliances in my home that should be heat pumps. My dryer, which has horrible ducting issues and consumes massive amounts of electricity and heats the house and pumps the cold air outside. In addition to the dryer I have an electric water heater in the garage that would be fantastic as a heat pump. It would partially cool the garage and most importantly consume some of the heat in the garage for water heating purposes.
You can go to googles sunroof project website to see how much footage/mwh a fully sunned home in your area would get. It's been a while but I think they give you kwh, from there depending on the (if in us) eGrid you'd be on you'd be able to see if there would be a meaningful difference in a) energy you'd be saving or generating and b) how bad your average grid is.
The Epa also publishes a tool called power profiler that can help you.
The answer is always yes. Heat pumps produce more energy transfer than they consume, giving you higher performance per input.
If you have a natural source of renewable heat (geothermal, solar, etc) then the heat pump only needs to be installed properly to supplement that primary heat source or leverage the heat source (if it’s not capable of being the primary source)
You could argue that it is less beneficial if you get electricity from a coal plant but could heat directly with natural gas or oil. The long term benefit comes from the heat pump’s ability to use any fuel without you spending a dime on new equipment. For example - a 92% AFUE gas furnace or high efficiency oil furnace will never pollute less than the day it’s installed. An electric heat pump may not be ideal when you are fueling it with coal, but when that source gives way to nuclear, solar, or wind your installed heating device will instantly be better (than the gas or oil fueled system) without spending a single cent on your local equipment.