Myth: Heat Pumps are not efficient in cold weather

We have been conditioned to expect our appliances to cycle. The refrigerator turns off and on. The basement sump pump cycles. The clothes dryer runs until the clothes are dry and then turns off with a friendly melody letting you know that it has completed its job. If any of these machines did not cycle off as we expect, we would naturally think something is wrong. So when the weather gets cold and your heat pump runs constantly, myths are born. Like, “A heat pump is not efficient in cold weather” or “Turn off the heat pump when it gets cold” or “Heat pumps are not designed for cold weather climates.” All myths! Hopefully you have only heard these misunderstood rants from neighbors or the “expert know-it-all” at work. But if you’re hearing any of these myths from your heating contractor, you have some additional problems. If you’re hearing these profound “truths” from your spouse, then they are absolutely true, but you might accidentally leave this blog open on the home PC.

Here’s the truth. Heat pumps are tremendously efficient, even in cold weather. True, the efficiency does decline slightly as the temperature goes down, but even at very cold, single digit temps, heat pump efficiency is impressive and always better than any other setting on your thermostat. Do not turn the heat pump off by switching to Em. Ht. (Emergency Heat). Assuming your heat pump is working properly, never listen to any service technician who suggests “giving the heat pump a rest” unless you want to pay two or three times the cost on your electric bill.

So if heat pumps are so efficient, then why do they run all the time? Here is a blog from the past with more information on this.

But what if my heat pump really is broke and running non-stop? How will I know if I need service? Here are some tips to keep you from calling for service every time it gets cold.

But hold on! Not only does my heat pump run all day and all night, but when it does get cold outside, my home feels colder! What about that Mr. Heat Pump Expert?!

Great question. Here’s why. Your thermostat prioritizes the heat pump run time to maximize the cheap heat. The auxiliary heat (electric resistance heat, or back-up heat) is minimized since it is more expensive. Here’s how it works. Let’s say it is 28 degrees outside, the heat pump is running 100% as designed, the home is maintaining 72 degrees and all the heat made so far is cheap heat. Now let’s say it cools to 26 degrees outside. If the home temperature goes down one, or sometimes two degrees, this causes the thermostat to bring on the auxiliary heat for a very short boost to supplement the heat pump. The home temperature raises to a point just short of the thermostat set point and then the auxiliary heat turns off as soon as possible. Meanwhile the heat pump has been running non-stop throughout this time to maximize the cheap heat. So in cold temperatures, the heat pump runs non stop to maximize your cheap heat but your home may remain a degree or two below your thermostat setting.

What should you do, suffer? NO! The heat pump is very efficient so make it do its thing. Simply turn up the thermostat a degree or two in cold weather so you are comfortable. Do not suffer and submit yourself to the old myth that heat pump homes are cold. (I’ve heard service techs poorly advise customers, “Sorry, you will just have to get used to it”.) Remember, you are not really splurging or abusing the environment by adding one or two degrees. In very cold weather, adjusting a heat pump thermostat to 73 may be necessary to provide the 72 degree comfort you were initially looking for.

One tip that is not a myth. Resist cranking your heat pump thermostat by more than two degrees at a time. If you do this frequently, you will be calling up the expensive heat to accommodate the fast blast of heat. This will not hurt your heating system but it can raise your bill if you do this often.

More questions? Call Precision Comfort Systems. We’re the honest ones with much more precise information on your comfort systems.

About Energy Man Dan


6 Responses to “Myth: Heat Pumps are not efficient in cold weather”
  1. Joe says:

    I know this article is a year old.( Myth: Heat Pumps are not efficient in cold weather) However my question is very close to your example. I live in NC and have a heat pump. It’s 27 outside. My tstat is set at 68 and as you stated the pump doesn’t stop. It was 66 in the house at 6 AM and is still 66 at 10 AM. I just spent over $12,000 on a new system that was completed last week and the auxiliary seems to be always on. I thought I would check once more before I hit send and it is now 67 in the house. Does this sound correct to you?
    PS the house is 2000 square feet and well insulated.

    • Energy Man Dan says:

      Joe, your system sounds like I have described above, where it has hit the balance point and is now attempting to give you as much of the cheap heat as possible. However, what if the heat pump really is broke? I am concerned that you say the auxiliary is always on. So read this blog: regarding a Heat Pump DIY Test.
      Here is the test from that blog. The outside unit is connected to the inside furnace by two copper refrigerant lines. One is the size of your thumb, the other the size of your little finger. In the winter, when the outside unit is running, feel the larger of the two copper lines. It is probably covered by a black foam insulation, so you will need to get under this foam to feel the metal pipe. This line should be very warm to the touch. It will not burn you, but on most winter days above 20 degrees, you will want to pull your finger off pretty quick. If it is not hot, the heat pump may not be working.

  2. DonL says:

    I like how you mention “know it alls”. If you heat pump is running continuously and is a singe stage, (most are) then it is producing all the heat it can. Know it all dummies, undersize heat pumps to get the job or because of un-true rumors. I did not fall for that. My heat pump cuts on and off even with 10 degrees F outside. It running all the time is a sure sign the heat pump is too small or defective. Let’s take this to Myth-busters!

    • Energy Man Dan says:

      Don, we disagree. The myth I am trying to explain is that heat pumps are broke or undersized if they run all the time. This is not true. In the Midwest, heat pumps are designed and sized to run all the time in temperatures 30 degrees and below. A heat pump that is still cycling off and on at 10 degrees is probably oversized. An oversized heat pump will cost more to purchase and may cause you problems in the summer cooling season. Even though the heat pump is running non-stop in the colder temperatures, it is still 2 to 3 times better than the auxiliary electric heat. A properly sized heat pump will provide about 85% of the winter heat needed by your home. An oversized system may very well provide 90% of the winter heat, but now you spend too much initially and you need much larger ducts for proper airflow.
      Heads up if you are replacing your heat pump! When you change out your system, do not fall for the line that your old system appears to be undersized since it was running non-stop. This expert will stuff a 4 ton system on your 3 ton duct system and it will never work properly. Properly sized heat pumps run 24/7 in cold weather. It’s OK!

      • DonL says:

        You are wrong! If a heat pump is running all the time, it is too small. You need to re-think this.

        • Energy Man Dan says:

          OK, I have re-thought this and have come to the conclusion that your opinion is exactly why people rely on the heat pump experts at Precision Comfort Systems. We help customers understand how heat pumps are intended to operate and correct the misinformation preached by others. Thanks for participating in our blog as it helps to support our claim that not all the “help” our clients receive is correct.

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