Why Are Heat Pumps Less Efficient in Extremely Cold Temperatures?

Last week, our service territory saw temperatures in the single digits and negative-degree wind chills. When temperatures drop like that, some heating systems, such as heat pumps, either don’t work well or work double time to keep up with the thermostat.

Heat pumps are not as efficient during frigid temperatures because they rely on the transfer of heat rather than the generation of heat. In other words, they work by moving heat from one place to another rather than creating heat through combustion or resistance.

Heat pumps are most efficient when the temperature difference between the inside and outside of a building is small. When it’s extremely cold outside, the temperature difference is large, which makes it harder for the heat pump to transfer heat effectively. As a result, the heat pump may have to work harder and use more energy to maintain a comfortable indoor temperature, which can reduce its overall efficiency.

Also, every heat pump system includes a “heat strip” component. These strips, are designed with more traditional technology, are coil-like elements that generate heat when electricity flows through them. When your system fan blows air across them, these strips distribute that heat out into your home.
Heat strips are much less energy efficient than a heat pump. This is why heat strips are designed into these systems for auxiliary or emergency use. When the outside temperature gets too low for the heat pump to work effectively, as mentioned above, the system kicks the heat strips into operation, supplying any needed supplemental heat so the heat pump can keep pace.

It’s important to note that heat strips need a lot more energy to run compared to a heat pump. For this reason, relying on heat strips for an extended amount of time can drive up your electric bill.

The graph pictured shows the electric use of a home with a heat pump and auxiliary strip heat. You can see that the lower the temperature (blue line) gets, the higher the usage (green bar.) There are many reasons why electric use changes, the primary reason for the significant change in usage shown in the graph is because of this home’s heating system. The heat pump couldn’t keep up with the drastic drop in temperature, so the auxiliary heat strips kicked on, which caused an increase in usage.

Keep in mind that situations like this may very well affect your electric bill. Members looking to be mindful of their usage and wanting to reduce the impact on future bills should follow these tips:

  • Monitor your energy usage- You can easily monitor your usage by using our mobile app or through the member portal on our website. By monitoring your usage, you can identify areas where consumption has spiked and work to reduce it.
  • Use energy efficient appliances-Energy efficient appliances use less energy than traditional appliances and energy-efficient appliances are often designed with better quality components, which means they tend to last longer than traditional appliances.
  • Turn off and unplug- Simple actions like turning off lights and unplugging any unnecessary appliances when they’re not in use can save you energy and money over time.
  • Insulate your home- Proper insulation can help keep the heat in and cold out, which can reduce the amount of energy needed to heat your home, (and keep your heating systems from having to work twice as hard to meet the set temperature on your thermostat.)

For more tips to reduce usage and save money, visit our Ways to Save webpage or the Energy Saver website.