Is Solar Heating of Pool worth it? Especially after Time of Use (TOU) electric rates are introduced?
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.
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
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.