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My 20 year old air conditioner recently died and I was looking into replacements. In my climate the temperature ranges from 40C in the summer, and -40C in the

• nielsbot 3y ago
  -40C? That's an extreme situation. Heat pumps can be installed with backup heating as I understand it.
  • Alupis 3y ago
    > Heat pumps can be installed with backup heating as I understand it. Then, what's the point? If you still have to have gas lines and infra, just use the gas. It's vastly cheaper.
    • mason55 3y ago
      > Then, what's the point? If you still have to have gas lines and infra, just use the gas. It's vastly cheaper. A) Not everywhere B) Heat pumps can be powered with solar, reducing costs even if your gas would normally be cheaper C) Some people are willing to spend a little more if it helps push electrification forward, for environmental reasons
      • frumper 3y ago
        I tend to need heat when the sun isn't warming everything up.
      • Alupis 3y ago
        > Some people are willing to spend a little more if it helps push electrification forward, for environmental reasons It's not a little more though, that was the point. In my area, California, it's about 4x more. Gas here is so cheap, it's almost free. Anecdotally, I don't know anyone who's opted into the "green energy" plans offered by the area's utility providers - because they all cost a lot more than regular. People talk a lot - but their bank account dictates their actual decision making. Running a heatpump seems very expensive for a lot of the country, with negligible gains. Natural Gas isn't exactly what we would call "dirty"... seems like a min-max issue, with people forgetting there's still areas burning coil and oil for electricity production. > Heat pumps can be powered with solar Not in the dead of winter you can't... not everyone lives in big cities folks, and where it snows, it gets quite cold.
        • ThatPlayer 3y ago
          Lots of places are looking into phasing out natural gas though. California gives you rebates for heat pump water heaters and there's plenty of discouragement to block new gas appliances and hookups. There will be a feedback loop once that really starts: individual prices go up because infrastructure costs remain the same, but less people are using gas. Once natural gas prices go up, people will switch to more efficient appliances, or switch to electricity. Forcing prices to go up some more to make up for infrastructure costs. I agree with you about people following their wallets and that's why people will want to change to heat pumps when gas becomes too expensive. Remember the prices in December?
      • zamalek 3y ago
        D) Carries the risk of killing you with CO.
    • baseballdork 3y ago
      > Then, what's the point? Minimizing your gas use?
    • dtgriscom 3y ago
      That depends on the temperature difference. For smaller differences, heat pumps are much more efficient, but at some level they lose efficiency and gas is cheaper.
  • usrnm 3y ago
    > That's an extreme situation Depends on where you live
    • loeg 3y ago
      It's an extreme climate that ever reaches -40.
    • galangalalgol 3y ago
      Its 48C down to -10C here. Some years get down to -18, but not enough to build for it. That extra 8C has a qualitative difference to the steps that need to be taken for people and structures. The problem this year has been high humidity at that high end, much more than normal. When you have over 40% relative humidity and its over 45C it makes air conditioners work extra hard due the specific heat of the water vapor they are cooling. There were some dessication technologies being talked about last year that would really help as they operated prior to cooling the air but I haven't seen them rolled out yet. I've heard anecdotes about EVs refusing to operate due to battery safety, and public transit shutting down due to insufficient cooling capacity.
    • nerdbert 3y ago
      A vanishingly tiny percentage of the world population lives somewhere that regularly reaches -40°.
  • xeonmc 3y ago
    Fahrenheit or Celsius?
    • NovemberWhiskey 3y ago
      It doesn't matter.
    • abulman 3y ago
      Yes.
    • scq 3y ago
      -40 is the one value where Fahrenheit and Celsius line up exactly.
    • kuchenbecker 3y ago
      [flagged]
  • ZeroGravitas 3y ago
    You also get "hybrid" heatpumps that work alongside other sources of heat.
• martythemaniak 3y ago
  Same situation, but I'm looking to replace the AC with a HP. For a little extra money, you get the flexibility to choose your heat source. Newer thermostats can be programmed to switch between the power sources and you can hedge against one price fluctuations in one of the power sources.
• mason55 3y ago
  Is that the typical range in a normal year? Or is that the all-time extreme record? One thing people tend to do when they look at heat pumps is look at the typical extreme low for the year and size the heat pump based on that. But even if you touch -20 a few times a year, your heat pump doesn't need to be sized to heat in a constant -20. If you hit -20 once or twice per year then it's usually only for a few hours and the lowest that you really need to heat through is usually much closer to -10 or higher. But, yes, if you're in a climate that sees frequent and sustained temps of -40 then a heat pump probably isn't for you or the rest of the Canadian Prairies.
  • fireflash38 3y ago
    Your best bet is also to spend a lot more on insulation. Combined insulation and efficient heating/cooling will keep your house comfortable. Overspending on one will not be as good. You can also do heat pump for 90% of the time and emergency heat as oil/gas/wood stove.
• thsksbd 3y ago
  Where do you live (general area) that you get -40 C often enough for it to matter? Do you mean real -40? Or wind chill "-40" which doesnt affect HP? Edit: Edmonton?
• bfuller 3y ago
  Heat pumps require more specialized techs to work on them too.
  • lsaferite 3y ago
    HVAC techs can work on Heat Pumps just as well as on dedicated ACs. They are not significantly different.
• Casteil 3y ago
  Similar climate here, although days it gets below -10f / -23c are uncommon. Most winter days in a climate like this you could heat with a modern/high tech heat pump, but: - It's probably going to be more expensive than heating with natural gas if you're in the northern US - at least as things are today. - A modern/high tech heat pump capable of heating when the outdoor temp is < 10f / -12c is likely going to be quite a bit more expensive than a standard AC unit - making it even more difficult to justify financially - A natural gas furnace can keep you warm (and keep your pipes from freezing/bursting) even if there's a power outage. It doesn't take much of a generator to run a furnace/blower fan.. but good luck staying warm with ONLY a heat pump in those circumstances. The one thing that can really help improve the financials of getting a heat pump is if you intend to install solar power at some point in the future. Depending on your power company, you may be able to generate enough credit in summer with excess generation to pay for heat the entire winter. I'd still go with a heat pump AND gas furnace for backup though.
  • fireflash38 3y ago
    > I'd still go with a heat pump AND gas furnace for backup though. Thankfully, this isn't too expensive of an option to do. Gas furnaces are cheap. Heat pump that isn't sized to go to -40F/C is also pretty affordable. The crazy high SEER ratings drive up the price.
• loeg 3y ago
  Most people live somewhere with vastly milder winters. Generalizing from your -40C winters is not useful.
  • web3-is-a-scam 3y ago
    Not generalizing, just saying if you live in a place with more extremes in the climate than a heat pump may not be ideal.
• xenadu02 3y ago
  There is zero reason not to get a dual heat system. A heat pump vs pure cooling A/C is mostly just a reversing valve. There is almost no difference between the two which makes sense: A/Cs are just heat pumps setup to move heat outside the home. A "heat pump" heating system simply runs the other direction to move heat inside the home. Either way it is standard vapor compression with a compressor, two coils, and two coil fans. Modern heat pump systems have an outdoor temp sensor and will avoid even trying the heat pump if it is too cold outside. Your installer should be able to adjust that setpoint. How low it can go depends on the refrigerant and rating... in the US higher SEER ratings often also means it can extract useful heat at lower outdoor temps. tl;dr: The heat pump function is a trivial bit of material addition to a standard A/C and saves you gas/electricity even if it is only used for part of the cold season. There is no reason not to use one.
  • amluto 3y ago
    As a (small) reason, the controls involved in operating a heat pump plus furnace/fan are more complex than the controls involved in operating a plain air conditioner plus furnace/fan. (Possibly more than a little more complex if the heat pump is only operable under certain conditions and the heat pump and/or furnace is multi-stage or actually variable speed.). HVAC controls are very solidly stuck in the 1980s (or 1950s or whatever), with the main exception of highly integrated and proprietary variable speed heat pump controls. I say this as someone who recently helped undo the damage after an inept HVAC technician replaced someone’s thermostat (for $500, thanks California prices) and did it wrong. The quality of the instruction manuals is low, and the quality of online resources about how conventional HVAC controls work is lower. As far as I can tell, the theory is that HVAC systems used to consist of a bunch of discrete components, strung together, with control power coming from one or two transformers or thermocouples [0], and essentially no logic in the equipment. A relatively modern heat pump may well rely on a mechanism in the thermostat to protect the compressor. The actual equipment contains nothing resembling a microcontroller. [0] Yes, the actual power available from the equipment to the thermostat may be negligible, and old thermostats were mercury switches on bimetallic strips that were powered solely by temperature changes in the room.
• Darrengineer 3y ago
  I’m curious which areas this occurs on earth and what percent of population live there. I would guess a negligible portion. In the US, I would think it’s almost nonexistent. I’m from Minnesota and went to university in North Dakota - places with some of the coldest and most severe winters in the US. +40C in the summer and somewhat regularly down to -40C windchill temperature in the winter. If it were me, a place with actual air temperature of -40C with any kind of wind occurring would require multiple forms of heating for me to consider it safe for my family relying on only one or even two sources of heat doesn’t seem reasonable.