I found a nice 100k btu heater DSI for $200. My pool is 15x30 with a deap end, so I think I figured 13000gallons or so.
My primary heating method is solar, I have 7 panels active right now, and it's doing a great job on warm days with sunshine. It's starting to turn colder at night, sometimes in the 40's, so it's got me thinking about this part of the season.
I realize that a 400k btu would be better, and I believe the btu to cost relationship isn't totally linear (ie: 400 will not necessarily use more propane than a 100 for the same rise in temp.)
Ultimately, I'm trying to decide of adding a heat pump instead would be worth it, or to just use the propane heater as a quick way for the weekend or whatever. At $2.25+ gallon (ie: per hour), it's expensive, and electricity is cheap. We actually run a hybrid system for our furnace that runs heat pump down to 25 degrees, then switches to propane.
With the solar, we may only use the heat pump for the early 3-4 weeks and the late 3-4 weeks.
Anyway, can someone throw some advice to me?