A few more bits of useful info for this setup: - Most Heat pump water heaters have a 3000W-6000W backup resistance element used when conditions are too cold to

A few more bits of useful info for this setup: - Most Heat pump water heaters have a 3000W-6000W backup resistance element used when conditions are too cold to run the heat pump. If you live in an area with long stretches of near or below freezing weather, make sure you install it in a conditioned or semi-conditioned space. - The exception is the Sanden C02 system which can heat water even in sub-zero temps. - Heat pump water heaters draw about 800W / 4A when using their heat pump, although probably more for the Sanden. As with most fixed speed compressors, the inrush/surge current can be as much as 4x the steady current, which is important for sizing the wiring and circuit breakers, as well as sizing max current output of any batteries that might be installed. - Heat pump water heaters have slower recovery times than gas fired water heaters.