I have 2 houses with indoor heated pools and the average cost is about $200 a month per house in propane to keep each one heated to 85 degrees.  Renters complain any time the water temp is under about 82 and even sometimes when the water is 85.  I installed floating thermometers in the pools so the renters could see for themselves that the water is 85.  A lot of times, they are expecting hot tubs with 25,000 gallons of water in them.  I don't see any way you can charge for additional heating costs.  Build that into your rate.  Pool houses typically run $100 a day more than a non-pool house and that is to cover the costs of heating it, maintaining it, chemicals, servicing etc.

Rick

www.vacationrentalhelper.com

I'm just buying a rental home in Orlando, where every house has a pool. The customary charge is $25/night for pool heat for the duration of the stay. Most of the year, the renter can just elect not to have it.

I'm also going to be installing solar panels that would provide free heating more of the year, so I can keep my costs down and also for the guests. In winter months, heating the pool is pretty much compulsary, but not everyone wants to pay to heat it, so adding that $25/night in makes it more difficult. Again, it's common in Orlando, so it's eaiser.