Your hot tub electricity cost depends on a few factors: unit price per kilowatt hour, the temperature you heat the hot tub to and how often the tub is used. In advanced testing, we have found that it typically costs less than $1 per day to run a hot tub, with more recent spa models hovering around $23 per month. On the other hand, we've all heard horror stories of old hot tubs costing well over $50 a month to run, but that has not been our experience. Energy-efficiency in hot tubs has come a long way over the last decade.