> my friend is building his house and is putting in 4 heat pumps (big house). The problem is we just lost power for 4 days and 2 years ago we lost power for 5 d

> my friend is building his house and is putting in 4 heat pumps (big house). The problem is we just lost power for 4 days and 2 years ago we lost power for 5 days. He is discovering that electric heat uses massive amounts of electricity and there is no way to get a residential generator big enough to power them all. He might not even be able to power one (they can use in excess of 20kw). If he's building the house new, he should strongly consider investing in designing the building envelope in a way that 20kW heat pumps aren't required. It's very possible, especially with new builds. The models to follow are Passive House [1] and Pretty Good House [2]. There are many examples of large houses built to those standards in cold climates that use a heat pump that only draws 2kW, which could easily be powered by a generator or backup battery. This assumes that by "big house" we mean something still below ~3500sqft and not some kind of mansion. The basics are to get the building air leakage below 1ACH50 (3-5x better than most codes, but not hard in a new build), and eliminate thermal bridging by using thick exterior insulation around the building perimeter. 1. https://passivehouse.com/ https://passivehouse.com/ 2. https://www.prettygoodhouse.org/ https://www.prettygoodhouse.org/