Regarding the previous post. I've had various different chats with local solar folks on this and their suggestion has spend the money and/or space you'd use on solar water heating on PV if grid-tied. The idea is if you go with a heat pump water heater or if you go with a tankless heater with small diameter hot pipes (1/2 or 3/8) to increase FPM water travel to reduce time to delivery and reduce surface area of the pipe that you'd save more than using a solar hot water tank with an electric backup heater because the PV will capture energy when the hot water system might otherwise not be able to capture it while maintaining a lower initial cost(equipment, piping, pumps, labor, water permit) and get a more reliable setup with less maintenance. The cost of PV has dropped but water heat hasn't. I suppose in areas other than MN where the sun shines more consistently with less snow cover it might make more sense but at the same time that PV would capture more too. Solar hot water with integrated space heat would be an exception to this because you're likely to use more of the energy available for capture, although a system sized for that would be more of a waste in the summer unless you have a process heat use or absorption chiller.
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