Hi! I recently bought a house with a pool. First house and first pool! My newphews are visiting for a week over Christmas and I'd like to heat the pool to about 85 during that week. It's currently at 70. I have a Hayward heater. Any guesstimates as to what that might cost? Hundreds? Thousands? I really have no idea. Half the people I've talked to said it won't cost much. The other half look at me like I'm crazy to even consider heating the pool because it will cost so much. The pool is about 9,000 gallons and I don't have a cover. Thanks!!!