It depends on the type of heat that you use. Typically a pool will add $20-30 a month to your electricity and the gas for the heat will increase by a like amount. However there are great solar covers that heat the pool. I used to bring my pool up to 78 degrees and then turn the heater off for the rest of the season. If you heat it year round then the cost will be greater. The best way to heat a hot tub is with 220 electric, the combined cost for heating and running the system is about $30 a month.
Then you need to consider chemicals but that usually is around $10-20/month. A pool service for maintenance is about $100-150/month but you can do most of the work yourself.