Is it true that heat pumps stop working when it gets very cold out?
Yes – but it would have to get very, very cold for a heat pump to stop working entirely. Different models of heat pumps have different ratings for how cold it can be before they stop being effective.
Heat pumps are rated for “output.” In this example, when it is 30 degrees out, a heat pump will easily produce 100% of its output at the highest efficiency. However, as temperatures start dropping, output starts dropping as well – and when output starts dropping, the heat pump will “work harder” to keep your home at temperature. Much like having to put your foot on the gas to get your car up a steep hill, this is where efficiency rates of heat pumps start to drop – more energy is used to produce less output.
In older houses with less insulation, large amounts of heat loss, or drafts, a heat pump will also need to work harder to accommodate the rapid loss of heat due to these issues. However, newer homes often have outstanding insulation and are built to prevent heat loss – in these cases, the heat created by a heat pump is kept inside the home and helps the heat pump perform with greater efficiency.