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I'm thinking of getting solar heating for my pool. We're in San Diego and the cost would be about $6000. Currently, I don't heat the pool at all as it's prohibitively expensive with natural gas. I am led to believe that the cost of running the solar heating is fairly negligible. Currently, I have to run the pump about 6 hours a day anyway to circulate and filter the water. I would have to pump the water to the roof to get heated which requires the pump (variable speed modern pump - PenAir) to work a little harder and thus use more electricity. However, this is all based on electricity being the same cost throughout the day. Obviously, the water must be pumped to and from the roof when the sun is shining (the higher in the sky the better). So my questions:

  1. How well does Solar Heating work?
  2. How many hours do you need to pump the water to the roof to heat the pool?

I'd hate to spend $6000 and find out that I can't use it. If/when Time of Use (TOU) becomes mandatory, it will be much more expensive to use electricity during the day. Right now, with no solar heating, that's not a big deal - I would just arrange to use the pump during off peak hours. However, that's not an option with solar heating (hence question #2). This brings me to my final question.

  1. Are people worried that there investment in solar heating will be not very good once Time of Use (TOU) becomes mandatory? It might be prohibitively expensive to pump water during the peak hours (typically something like noon - 6 pm). My understanding is that TOU will become mandatory in much (all) of the U.S.A. (I'm in California and 2018 is talked about as a possibility) The reasons why are a separate topic. I'm not sure if TOU already exists or is planned for the rest of the world. I'd be curious (but it's off topic :) ).

Thanks,

Dave

  • Your third question seems off topic, and should possibly be eliminated from your post. – Tester101 Jun 1 '15 at 23:22
  • Thanks for the quick reply! #3 is the question I most want answered! Depending on it's answer, answers to 1 and 2 are modified. That is, solar heating might not work well if it's prohibitively expensive to run it from 12-4p.m.! Thanks. – Dave Jun 1 '15 at 23:27
  • #3 is too localized, and would likely be answered more accurately by your local government (city/town hall, city/town/county clerk, etc.). – Tester101 Jun 1 '15 at 23:32
  • No, actually, TOU will be decided at the state level, at least in California. The local utilities have some leeway to implement things as they see fit, but within the general state guidelines. Thus the state will determine if TOU is mandatory or not, and when it comes into being. So it's a local question in that it applies only to California, however, California is a large portion of the population of the U.S. :) – Dave Jun 2 '15 at 0:35
  • It may well be a large potion of the US population, but it is not a large portion of the world population. Since this site is available worldwide (allegedly), even a question that may be relevant to all of California could still be too localized. – Tester101 Jun 2 '15 at 0:53
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  1. Heating a swimming pool is pretty much an ideal application for solar water heating. Relatively small delta-t requirements in mild weather means you can get high output from low cost solar collectors, and you can make use of 100% of the output. Payoff times for solar heating relative to equivalent natural gas heating can be as short as two years.
  2. You need to run the pump for most daylight hours, so in a San Diego summer, about 14 hours a day. You may be able to run your pump at a lower speed for circulation through the collectors, though, so this isn't necessarily a significant increase in operating cost
  3. Time of Use billing will certainly increase the operating cost of a solar pool heater, although not to the point that they aren't cost effective compared to other options, but perhaps past the point where you feel heating your pool is affordable. However, this can be effectively addressed with solar photovoltaic; aside from your standard grid tie solar PV, a DC pump can be tied to a few small solar panels without requiring an inverter, which can be cost effective even without peak TOU billing.
  • Thanks Zhentar. I've thought about the Solar DC Pump. Any recommendations or experience with brands? The other way to go would be to keep the existing pump (Pentair multispeed), buy some solar panels, a battery and an inverter, and run it that way. That would have the advantage of (1) keeping the same pump, (2) being able to run pump during night if necessary. I suspect some energy would be lost in the conversion (to battery, to inverter). – Dave Jun 4 '15 at 18:53
  • @Dave No, I don't have any particular recommendations. Inverter+Battery (or Inverter+Grid Tie) efficiency isn't too bad of a hit (you should still be able to do 80% or better if everything is matched right), it's mostly just a matter of complexity and cost; it can easily run more than a cost of a new DC pump (and you could probably resell your existing pump to further offset that) – Zhentar Jun 8 '15 at 0:33

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