You are not getting your money's worth. The PV is doing nothing but heating itself due to internal resistance.
For the same money you could elevate a 30 gallon drum in the sun, paint it black, and run your soon-to-be hot water through a small copper coil in the drum. You'd still have house pressure and not have to refill it much. Add an absorber plate below it to thermosiphon and heat the water in the drum, Some insulation on the North face, a little antifreeze just in case, and you'd have a first-class setup.
Rex