I've did portable generator installs on homes that have had gas furnaces and smaller heat pumps, so I've been fortunate enough to just use 10kw and below portables. However this house has a 5 ton Rheem unit with emergency heat.

Customer would like to go with a portable but has heard he may need to do a larger standby and get a propane tank on site, as they do not had natural gas in the neighborhood. The biggest portable that generac makes is 15kw running and I'm not sure if thats gonna be enough if they have to kick on the emergency heat when the heat pump is no longer effective.

I think they could get away with cooling on this size of generator but not heating. What are yalls thoughts?