COP or CoP means co-efficient of performance. An electric heater has a CoP of 1. New heat pumps usually have a CoP of 4 or higher. My 11 year old heat pumps hav

COP or CoP means co-efficient of performance. An electric heater has a CoP of 1. New heat pumps usually have a CoP of 4 or higher. My 11 year old heat pumps have a CoP of 3. This means they can produce 3 or 4 times as much heat as an electric heater, assuming the same amount of electricity, or produce the same amount of heat with 1/3 or 1/4 of the electricity. At a CoP of 3, they are more efficient than electric heaters down to -15C. At a CoP of 4, down to -25C. There are better heat pumps coming with a CoP of 5.