This doesn't answer your question, but I really wish someone would offer off-the-shelf panels with tubing on the back to hook up water lines. It would be dope to cool my panels and preheat my hot water at the same time.
Usually cheaper to just put more panels tho. Pretty handy if you need to get the most out of roof space but otherwise more panels + heat pump water heater is much simpler solution.
> The front side of the PVT heat pump panel is similar to a solar panel and has solar cells to generate electricity. The backside is a heat exchanger that supplies the energy source for the heat pump. The heat exchanger-collector collects energy form the ambient temperature and additionally from daylight and sunlight.
Not sure how it does throughout the whole season.
I've seen a DIY system where the panels are boxed in, and the hot air created behind the panels used for blown air / heat recovery heating.