What a hot tub costs to run

Across every size, the middle tub costs about $26 a month just to stay hot, at the US average rate. The cheapest tub we track to keep hot, the Caldera Spas Aventine, costs about $14; the most expensive, the American Whirlpool 982, about $46.

Your rate matters more than the tub. That middle tub costs $26 a month at the 18.19¢ US average; in North Dakota, the cheapest state at 12.36¢, it is $18, and in Hawaii, the dearest at 46.28¢, $67. Pick your state in the calculator.

The monthly figure above is the tub sitting covered and hot. Soaking with the jets on, leaving the cover off, cold nights and heating fresh water after a refill all add to it. A refill is the one you can put a number on: warming the median six-seater's 392 gallons from 55°F hose water to 102°F takes about 45 kWh, about $8, a few times a year. Every 10°F of warming costs about $2.

Heat leaves through the cover, the walls and the floor, and the heater runs to replace it. Among six- and seven-seaters, the gap between the cheapest and the dearest to keep hot is about $21 a month, or $249 a year. The difference is how well the shell, insulation and coverCoverThe insulated lid: a tapered foam core in a vinyl or fabric skin. Plan on a new one about every five years, and read the warranty's rules on covers.In the glossary → hold heat, and how little the pumps and controls draw while idle: see hot tub covers and hot tub insulation.