The evenings can be cool but the extra charge is very high for the week. We have a 14 x 28 inground pool, it costs $80 to heat per month in September when the temp was 75 during the day and 65 at night. That costs seems way too high. If you really want it see if they will reduce the cost. Or just pass. I remember one of our first stays at a townhouse at Windsor hills, I paid extra for pool heat only to find that the heater did not work. I called the owner. The first out of his mouth were don't call the pool company. He gave my spouse instructions on how to set the heater. My husband said it appeared the heater had not been working for sometime based on his experience with electronics. When I called the owner is seemed to act confused as though we did n't know what we were talking about. Overall I feel we were ripped off.