@Noelle144 I don't have pools, but I have rented homes with pools. In every case I have had to pay extra for a heated pool, which I am willing to do. If you have a good handle on what the additional cost would be and how much to raise your prices while staying competitive, great!
However... your guests will need to know what the maximum temprature is and how long it takes the pool to reach that temperature. If you turn the heat down (or off) between rentals, that time will become crucial as you do not want to be refunding a whole booking for a cold pool that CS thinks is a missing amenity.
You will not want guests to have access to the pool controls, so you may have to invest in a system that is controlled remotely, or that is locked and only you or your housekeeper can unlock and turn the heat up or down, on or off. Do not leave chemicals around either and do not let your guests backwash or otherwise "service" the pool.
You will also want to charge every guest for the pool, even if they do not use it. I used to have a winter hot tub fee that was optional. Many guests claimed to not want to use the hot tub and would not pay the fee. Guess again.