Backup heat sources are recommended and required when we install a heat pump. The main reason for these backup sources is that heat pumps can heat your home during the shoulder periods down to about -5°C to -20°C without any help. However, we still experience days as cold as -25°C, and in those circumstances, we need to ensure that our customers remain comfortable. Therefore, a backup heat source, such as natural gas, electric, or any other fuel source, is recommended. Keep in mind that these backup heat sources will be used minimally, only about 20% of the operating time during the winter periods.