If you're in WI, then it's only going to operate as a heat pump for maybe 1/2 the year. The other 1/2 it's just gonna be a standard electric water heater. As far as I know, they have the shortest lifetime, and with all of the electronics it's going to need a lot of maintenance/repairs ... kinda like when power vents came out, or when tankless units came out. I think if someone has a boiler, then indirect is always the way to go.