Emergency Heat or Not

By Patrick Phipps, JCPB Senior Energy Advisor

Should I switch my heat pump to emergency heat when it’s really cold?
During this cold spell, this question has come up. I have discussed this topic with several different contractors from our QCN list and heard two different opinions or theories.


Option 1:
Don’t worry about the cold weather and run the heat pump in its normal heat cycle. By continuing to operate the heat pump in its normal heat cycle the heat pump will run longer due to the cold temperatures and the auxiliary heat will occasionally come on, which is the way it’s supposed to work in really cold temperatures. Also, several contractors stated that they have been to HVAC manufacturing facilities and seen heat pumps tested at temperatures at 0° and below. These contractors were told, “they’re designed to operate at these temperatures.”


Option 2:
Some contractors believe that when temperatures get well below 30° for an extended time, the heat pump needs to be manually turned to emergency heat. These contractors believe this because the cold temperatures really lower the efficiency of the heat pump, it causes more “wear & tear” on the system, and the auxiliary heat is going to be on all the time anyway, so go ahead and do it.


Which one is right?
Good question and no one probably has the right answer, but there is one thing that is true about these two opinions. If you switch your system to emergency heat during these extreme cold times, it’s going to take more power (energy) to operate the system which means it’s going to cost you more money. A heat pump that has a 10 kW (10,000 watt) emergency heat coil will consume more energy than a heat pumps compressor even when it runs for an extended time and the auxiliary heat occasionally comes on. Keep in mind that although it may cost more to run the unit in emergency heat, the emergency heat may provide warmer air temperatures.


Which should I do?
It’s your choice and you’re the one paying the bills. The most energy efficient thing to do is to operate the system in its normal heat mode. The one thing that would be of the most importance is to make sure to have your HVAC system serviced annually and that is stay in good working conditioned. This may help prevent an unwanted breakdown during really cold or hot weather. Keep your cold air return filters changed monthly. Also, set your thermostat at one temperature and leave it. Do not frequently adjust the thermostat. Frequently adjusting your thermostat will increase your energy bill.