I was poking through my Thermostat's App a couple of weeks ago, and found a setting that said "Use Gas", "Use Heat Pump", and "Let system decide". I had thought our furnance was running the heat pump automatically... for the last 5 years. I switched, and now the display says "Heating with Heat Pump" and I'm a little upset that it wasn't more obvious before now.
Heat Pumps Take on Cold Climates
31–40 of 83 posts
Re: Heat Pumps Take on Cold Climates
#32As someone who switched to a heat pump recently, you should know "your mileage may vary." Don't confuse physical efficiency for cost efficiency. In many places, natural gas is still more cost efficient, even if it isn't as efficient in terms of physics.
As someone who switched four years ago to a heat pump plus conventional furnace, I can state from experience that my thermostat takes electricity cost per kWh and gas cost per therm (other units are available, these are just the ones that match my utility bills) and efficiency of both the heat pump and furnace and runs whichever is cheaper.
Gas cost has varied a bunch over the years I’ve had it, electricity less so. But the furnace has only run a few days per year and only when when it’s been (depending on gas cost) below 10 to -5 degrees Fahrenheit.
My heat pump (trane xv19) kicks ass and if I were doing the hvac upgrade again I’d skip the furnace entirely and let the heat pump work a little harder/longer on the coldest days.
It’s damned near always more cost-efficient to run the heat pump. And my shiny new high efficiency furnace will never, ever pay itself off saving me a few bucks a day the three or four days per year that the math works in its favor.
Re: Heat Pumps Take on Cold Climates
#33I recently had a Mitsubishi hyper heat installed to replace my natural gas furnace. The air handler is connected to the ducts so it was an easy transition. I live in Chicago so I also had 10kW resistive heat strips installed as a backup. This winter they never needed to come on, and I was able to keep the house at 70 degrees F even when we hit around 0 degrees F outside.
I haven't crunched all the numbers but so far my electricity bill has gone up by about as much as my gas bill has gone down, so there really isn't much savings there which is too bad. I mainly did this though for the environmental benefits, as I want to slowly phase out all natural gas in my home. Next step will be to replace my gas range with an induction cooker, and the last will be a heat pump water heater.
Re: Heat Pumps Take on Cold Climates
#34If you're considering a heat pump, be sure to check the minimum operating temperature before you buy, and/or make sure you have a backup heat source.
I live in a rented apartment with a mini-split, and it worked great for 363 of the last 365 days. Those two days, we had a sudden cold spell and temperatures went down to -6 F (which isn't that cold), but we found out the hard way that our unit was only rated to -4 F.
Once it went down to -5, the heat pump didn't just work less efficiently, it stopped working altogether. It was the only real heat source in the house. We tried turning on the kitchen oven for a while, but it couldn't keep up. We had to leave the apt for those days and crash with a friend.
Other than that, though, it's been wonderful! SO much nicer than other heat sources (furnaces, space heaters, etc.) It's comfortable, cheap, quiet, and has its own thermostat. We just leave it on and it does its thing and it's magical.
Re: Heat Pumps Take on Cold Climates
#35As someone who switched to a heat pump recently, you should know "your mileage may vary." Don't confuse physical efficiency for cost efficiency. In many places, natural gas is still more cost efficient, even if it isn't as efficient in terms of physics.
Especially if you get your electricity from PG&E, who charges ridiculously high transmission and distribution fees.
It makes financial sense in a lot of places to switch to solar plus battery for nearly all energy use. Especially if you can charge your EV directly from solar. Heat pumps at night and in the evening need the batteries though.
Re: Heat Pumps Take on Cold Climates
#36Is there a way to get your house (currently with hydronic gas heat) retrofitted for heat pumps that doesn’t result in either a ton of demo or ugly lines all over the exterior? I tried to switch over last year only to find the savings were not that great in my climate, and that it would have an unacceptable aesthetic cost.
> Is there a way to get your house (currently with hydronic gas heat) retrofitted for heat pumps that doesn’t result in either a ton of demo or ugly lines all over the exterior? It's literally the same physical design as an air conditioner. So... yes, unless you hate seeing AC units too, I guess.
A house with hydronic gas heat probably doesn’t have ducts right now. An owner of a house asking how to retrofit a heatpump without a ton of demo increases the likelihood that their house doesn't have ducts.
Adding ducts to an existing house qualifies as a ton of demo in virtually every case.
Re: Heat Pumps Take on Cold Climates
#37As someone who switched to a heat pump recently, you should know "your mileage may vary." Don't confuse physical efficiency for cost efficiency. In many places, natural gas is still more cost efficient, even if it isn't as efficient in terms of physics.
As someone who switched four years ago to a heat pump plus conventional furnace, I can state from experience that my thermostat takes electricity cost per kWh and gas cost per therm (other units are available, these are just the ones that match my utility bills) and efficiency of both the heat pump and furnace and runs whichever is cheaper. Gas cost has varied a bunch over the years I’ve had it, electricity less so.…
It really depends on your area's natural gas vs electricity prices, which can vary wildly.
Electricity can range from 11¢/kWh to 29¢/kWh in California or higher: https://www.energybot.com/electricity-rates/
Natural gas ranges from (converted) ~ 2¢/kWh to 8¢/kWh in Florida: https://www.eia.gov/energyexplained/natural-gas/prices.php (using conversion factors from https://www.nrg.com/resources/energy-tools/energy-conversion..., which I think assumes 1000 ft^3 ~= 1 therm ~= 29.3 kWh)
So your heat pump's COP has to exceed the ratio between natural gas and electricity in your area to make it cost-effective (or you can get solar + battery backup).
Electricity prices can vary quite a bit, too... in Cali, for example, it's gone up from 14¢ to 24¢ over 16 years, which is nearly double the rate of inflation.
Re: Heat Pumps Take on Cold Climates
#38Earlier quoted context omitted.
I think probably the ugly lineset covers characteristic of lowest possible budget (and therefore overwhelmingly most common) installation of air-to-air heat pumps.
I guess this depends on where you locate the heat pump. On mine, the insulated pipe and mains connection are within two feet of the building.
Is yours air-to-air?
Re: Heat Pumps Take on Cold Climates
#39I was poking through my Thermostat's App a couple of weeks ago, and found a setting that said "Use Gas", "Use Heat Pump", and "Let system decide". I had thought our furnance was running the heat pump automatically... for the last 5 years. I switched, and now the display says "Heating with Heat Pump" and I'm a little upset that it wasn't more obvious before now.
I feel you! There’s a lot of specifics that are hard to know without digging in and making mistakes!
I just found out my heat pump was configured incorrectly in the Nest Thermostat bc I have a Rheem and their heat cool valves are reversed from typical.
TLDR my January heating bill was $500 bc heat pump never came on!
Re: Heat Pumps Take on Cold Climates
#40> But heat pump manufacturers say they now have the technology to heat homes just as efficiently in bitter cold as they do in milder winter temperatures. This claim defies thermodynamics (and I expect better from IEEE). Heat pumps are bound to be less efficient as the spread between inside and outside temperature grows. (They might be just as effective or they might be just as efficient as current heat pump tech , bu…
My father has a heat pump that works fine in alpine climate (half of the winter snow outside) for more than a decade now. Not sure about the precise english terminology here, but his hear pump works using the deep ground water next to our house. The temperature of that water slightly dips in winter, but it is no more than a degree. It is a very old house that before had a oil heating system and I think the replacemen…
That’s a ground-source heat pump (often called geothermal heat pump). These have been around for decades in the U.S. but haven’t been very popular due to the 2-3x installed cost vs. an air source heat pump.