Modern inverter based heat pumps are perfectly fine to oversize. Since you can adjust the speed of the compressor, you just run the compressor slower if you wan

Modern inverter based heat pumps are perfectly fine to oversize. Since you can adjust the speed of the compressor, you just run the compressor slower if you want to 'undersize' it. There's little downside aside from cost to oversizing these days, and in many cases it may be necessary to oversize the cooling side to provide enough heating in the winter.