5 ms·

There are a lot of US households on places like New England and the Midwest where historically very very few houses have central air and most have a furnace run

There are a lot of US households on places like New England and the Midwest where historically very very few houses have central air and most have a furnace running on oil, propane, or natural gas. The upgrade path is hard there: do you accept the multiple thousands of dollars to install a heat pump on top of your existing heating solution? For the couple of fringe months where a heat pump can actually heat your house, and the extra cost of cooling in the summer (money many don't have)? It probably makes a lot of sense to just switch to a heat pump if you live in the south these days and give up any backup heating system entirely. But it is worth noting that only in the past 5 years or so did we finally get heat pumps that didn't totally suck at 0C. Until then, it made sense for even a lot of Southern households to stick with backup furnace + central air, assuming they already sunk money into the backup furnace for the 5 days a year they actually need it.

jandrese 4y ago
Heat pumps have always had a built-in resistive heating element as a backup option for when it gets too cold out. This is terribly energy inefficient, but if you're talking about a few days a year at most it is fine, no need to install a second heat source. Besides, 0C is far too conservative an estimate for heat pumps. -10C was no problem even for 30 year old units.
- michaelt 4y ago
  > Heat pumps have always had a built-in resistive heating element as a backup option for when it gets too cold out. This is terribly energy inefficient, but if you're talking about a few days a year at most it is fine, Won't it be a problem if heating becomes much less efficient across an entire city, just as demand for heat is at its highest?
  - js2 4y ago
    Indeed! In NC this past January, Duke Energy asked everyone to turn their thermostats down. NC has the one of the highest percentages of heat pumps in the country: https://news.duke-energy.com/releases/duke-energy-thanks-customers-for-help-during-cold-snap;-sets-all-time-records-for-winter-energy-use https://news.duke-energy.com/releases/duke-energy-thanks-cus... https://www.canarymedia.com/articles/heat-pumps/chart-which-states-have-the-most-heat-pumps https://www.canarymedia.com/articles/heat-pumps/chart-which-...
- 0cf8612b2e1e 4y ago
  Large parts of the country can be consistently below 0C for weeks at a time. Resistive heating cannot beat gas in that scenario.
  - SOLAR_FIELDS 4y ago
    True, but conversely a decent swath of the US population lives in Texas, where being under 0C for weeks at a time is a near impossibility. For those use cases heat pumps work great (assuming you don’t have a failed state on its own grid that will fall over at the slightest whiff of abnormality, of course).
  - PaulDavisThe1st 4y ago
    Modern air source heat pumps will not be using resistive heating in most winter weather across the USA. A Mitsubishi Hyper unit still has a COP of 1.0 at 5F.
    - maxerickson 4y ago
      Resistive heat has a COP of 1.0. So that heat pump loses its advantage at 5 ⁰F.
      - PaulDavisThe1st 4y ago
        I didn't say that they still had an advantage, I said that switching to resistive heat was unlikely for most winter weather across most of the US.
        maxerickson 4y ago
        "Still has a COP of 1.0" implies it is still doing something is all. It would be clearer to just say that it works down to 5. I'm not in the coldest regions and would be using resistive heat many nights of 3 months with that performance.
        4y ago
cduzz 4y ago
I'm in that situation -- oil burning furnace with forced air. It's a 1980s vintage system with an outdoor double walled oil tank. I could replace the furnace with an air source heat pump. But it turns out the people in the 1970s who designed the system weren't really on-the-ball. There's insufficient return, it's not balanced such that it's way hotter upstairs than down, etc. Further, if I wanted to blow cold air through the system I'd probably collect lots of moisture on the vents because it gets humid in the summer. The solution, though, is multi-zone mini splits that just pump the refrigerant around and expand / compress it where I want the heat/cooling; that gets rid of the big noisy air handler, allows my system to be a multi-zone system, and generally seems like a much better design. And with modern heat pumps, I don't think even in new england I'd need backup resistive heating.
xattt 4y ago
Though not in the US, Elliot Lake, a planned uranium mining community turned retirement village was built around the “nuclear model” of electricity production — ie that a base load was always available. Many houses in the community still have their 1970s-era heat pumps.
daydream 4y ago
> For the couple of fringe months where a heat pump can actually heat your house Heat pumps can heat throughout the entire winter in most of New England. The idea that they can’t keep up when it gets cold just isn’t true with new technology. New England had a day and a half or so this earlier this year where temperatures got as low as -10F (F, not Celsius). Afterwards a newspaper did an informal poll of heat pump owners. The overwhelming majority (IIRC 90%) of respondents said their heat pumps kept up fine. Keep in mind not all of these installs were the latest and greatest tech either.
- ygra 4y ago
  Insulation is probably the more important factor. If you don't lose too much heat to the outside, the heat pump doesn't even have to do that much. Or any other heat source, for that matter.
- vanilla_nut 4y ago
  Good point. Most of New England is just not that cold any more. Where I live in Northern New England, we got down to -20, almost -30 during that cold snap. And had a lot of sustained 0-ish temps throughout the winter. I wouldn't be comfortable using only a heat pump as a fuel source in my 1800s house. But I suspect it would likely keep the pipes from freezing. My relationship might not survive it, though. Better to keep the propane heat source for now :)

jandrese 4y ago

Heat pumps have always had a built-in resistive heating element as a backup option for when it gets too cold out. This is terribly energy inefficient, but if you're talking about a few days a year at most it is fine, no need to install a second heat source. Besides, 0C is far too conservative an estimate for heat pumps. -10C was no problem even for 30 year old units.

michaelt 4y ago
> Heat pumps have always had a built-in resistive heating element as a backup option for when it gets too cold out. This is terribly energy inefficient, but if you're talking about a few days a year at most it is fine, Won't it be a problem if heating becomes much less efficient across an entire city, just as demand for heat is at its highest?
- js2 4y ago
  Indeed! In NC this past January, Duke Energy asked everyone to turn their thermostats down. NC has the one of the highest percentages of heat pumps in the country: https://news.duke-energy.com/releases/duke-energy-thanks-customers-for-help-during-cold-snap;-sets-all-time-records-for-winter-energy-use https://news.duke-energy.com/releases/duke-energy-thanks-cus... https://www.canarymedia.com/articles/heat-pumps/chart-which-states-have-the-most-heat-pumps https://www.canarymedia.com/articles/heat-pumps/chart-which-...
0cf8612b2e1e 4y ago
Large parts of the country can be consistently below 0C for weeks at a time. Resistive heating cannot beat gas in that scenario.
- SOLAR_FIELDS 4y ago
  True, but conversely a decent swath of the US population lives in Texas, where being under 0C for weeks at a time is a near impossibility. For those use cases heat pumps work great (assuming you don’t have a failed state on its own grid that will fall over at the slightest whiff of abnormality, of course).
- PaulDavisThe1st 4y ago
  Modern air source heat pumps will not be using resistive heating in most winter weather across the USA. A Mitsubishi Hyper unit still has a COP of 1.0 at 5F.
  - maxerickson 4y ago
    Resistive heat has a COP of 1.0. So that heat pump loses its advantage at 5 ⁰F.
    - PaulDavisThe1st 4y ago
      I didn't say that they still had an advantage, I said that switching to resistive heat was unlikely for most winter weather across most of the US.
      - maxerickson 4y ago
        "Still has a COP of 1.0" implies it is still doing something is all. It would be clearer to just say that it works down to 5. I'm not in the coldest regions and would be using resistive heat many nights of 3 months with that performance.
        4y ago

cduzz 4y ago

I'm in that situation -- oil burning furnace with forced air. It's a 1980s vintage system with an outdoor double walled oil tank. I could replace the furnace with an air source heat pump. But it turns out the people in the 1970s who designed the system weren't really on-the-ball. There's insufficient return, it's not balanced such that it's way hotter upstairs than down, etc. Further, if I wanted to blow cold air through the system I'd probably collect lots of moisture on the vents because it gets humid in the summer. The solution, though, is multi-zone mini splits that just pump the refrigerant around and expand / compress it where I want the heat/cooling; that gets rid of the big noisy air handler, allows my system to be a multi-zone system, and generally seems like a much better design. And with modern heat pumps, I don't think even in new england I'd need backup resistive heating.

xattt 4y ago

Though not in the US, Elliot Lake, a planned uranium mining community turned retirement village was built around the “nuclear model” of electricity production — ie that a base load was always available. Many houses in the community still have their 1970s-era heat pumps.

daydream 4y ago

> For the couple of fringe months where a heat pump can actually heat your house Heat pumps can heat throughout the entire winter in most of New England. The idea that they can’t keep up when it gets cold just isn’t true with new technology. New England had a day and a half or so this earlier this year where temperatures got as low as -10F (F, not Celsius). Afterwards a newspaper did an informal poll of heat pump owners. The overwhelming majority (IIRC 90%) of respondents said their heat pumps kept up fine. Keep in mind not all of these installs were the latest and greatest tech either.

ygra 4y ago
Insulation is probably the more important factor. If you don't lose too much heat to the outside, the heat pump doesn't even have to do that much. Or any other heat source, for that matter.
vanilla_nut 4y ago
Good point. Most of New England is just not that cold any more. Where I live in Northern New England, we got down to -20, almost -30 during that cold snap. And had a lot of sustained 0-ish temps throughout the winter. I wouldn't be comfortable using only a heat pump as a fuel source in my 1800s house. But I suspect it would likely keep the pipes from freezing. My relationship might not survive it, though. Better to keep the propane heat source for now :)