Britain is much cooler during summer than anywhere in the lower 48. Most British houses resist hot weather very well, with thick brick walls and relatively small windows. You probably live in a modern apartment with a lot of glass and very little thermal mass.

One key advantage of heat pump systems is that they can often be run in reverse, serving as both heating and air conditioning. Currently a heat pump is no cheaper to run than gas central heating, but that is set to change within the next few years.