One note for anyone getting ready to switch to a heat pump water heater themselves: the fuckers are pretty loud. Make sure it's somewhere where the noise won't bother you when it's installed.

Newer models are getting quieter but the damn things are almost as loud as a small, modern window air conditioning unit when running.

Mine was installed right in the dead center of my house. Works great but I have to close several doors to not hear it at night (and I have it set up to mostly run overnight, though in someone else's situation it might be possible to have it run while everyone is out of the house at work or some such instead).