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Community and Q&A

Solar vs. Heat Pump Hot Water

nynick | Posted in Energy Efficiency and Durability on

I’m planning a renovation and had basically resigned myself to using a Heat Pump water heater like Rheem or AO Smith, located in the basement. While watering the garden yesterday I almost burned my hand on the water coming out of the hose that had been lying on the lawn!

It occurred to me that with our perfect south facing wall, a  small Solar Hot Water Collector system feeding a heat exchanger tank in the basement that then fed a standard electric hot water tank might make more sense. I’m guessing the costs, after relevant rebates, would be more or less the same.

What with the noise of heat pumps, the cost and the customer service complaints, a simple solar system may have more merit. There’s only two of us and the house will be more or less used spring, summer and fall.

What do you guys think?

TIA
Nick

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Replies

  1. Expert Member
    NICK KEENAN | | #1

    Solar thermal -- direct collection of solar heat -- is pretty much dead, it's getting hard to even buy the equipment any more. For a given amount of roof area you get more heat from a PV array and a heat pump. If you have net metering, it solves -- for you at least -- the biggest problem of solar, which is that the sun doesn't always shine when you need the energy.

    Smart people put a lot of thought into solar water heaters over the past five decades or so. The reason they never caught on is that the physics and economics never worked out. The exception is mild climates -- tropical or semi-tropical -- where the water only needs to be warmed a little bit above ambient temperature and you don't have to worry about freezing, so a simple tank on the roof painted black suffices.

    1. nynick | | #2

      This is really a shame. Such simple technology.
      Thank you for your reply.

      1. frontrange | | #3

        If you're interested in DIY projects, builditsolar.com has a lot of examples of solar water heating. There are some cases where solar water heating makes sense (e.g. pool heaters), but like DCContrarian said, net metering makes PV the much more sensible option in almost all cases.

        1. nynick | | #4

          Thanks. I actually used that website to build some hot air collectors that i use to heat my garage. I'll check it out.

  2. danjs | | #5

    > Solar thermal -- direct collection of solar heat -- is pretty much dead, it's getting hard to even buy the equipment any more. For a given amount of roof area you get more heat from a PV array and a heat pump.

    This is true, but at least one technology - photovoltaic thermal (PVT) - seems to get the best of both worlds by using a liquid cooling system to take heat off PV panels (which lose efficiency at higher temperatures), and then transferring that heat for domestic use. It will, however, result in overproduction of hot water in the summer, so it's better if you have a use case for that extra hot water (i.e. a swimming pool).

    https://www.homebuilding.co.uk/advice/solar-pvt

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