How Much Does a Hot Tub Cost to Run? A Realistic Estimate

Most of what a hot tub adds to your electric bill isn’t the time you spend in it. It’s the hours it spends sitting under its cover, holding a few hundred gallons at about 102 °F while the air around it is much colder. So the questions that matter are how well your tub holds heat, how cold it gets outside, and what you pay for electricity.

The number to find first: standby watts

Since June 1, 2019, portable electric spas sold in California have had to be tested for standby power: the average electricity used to hold 102 °F water with the cover on, in 60 °F air. The result goes on a label, and certified models are listed in the California Energy Commission’s appliance database. Many manufacturers also publish it on spec sheets, so you can often find it even if you live in another state.

If you can find that figure for your model, it’s the most useful single input for estimating cost.

California also sets a ceiling on it. For a standard spa holding V gallons, standby power can’t exceed 3.75 × V^(2/3) + 40 watts:

These are maximums for new spas sold in California, measured on a mild 60 °F day. Many certified models test well below the limit. Older spas, tired covers and cold climates can use much more.

What cold weather does

Heat leaks out faster as the gap between the water and the air widens. At the 60 °F test condition, 102 °F water is 42 degrees warmer than the air. On a 30 °F day, the gap is 72 degrees.

Our calculator scales standby power by that gap. It’s a simplification: filtration and electronics don’t follow the same rule. Here’s how one spa compares, with a labeled standby of 200 W and electricity at 18¢/kWh:

• 60 °F average outdoors: about 146 kWh a month, roughly $26.
• 30 °F average outdoors: about 343 W of standby, which is about 250 kWh a month, roughly $45.

Then add the jets. Four 30-minute soaks a week, with a jet pump drawing 1,500 W (an example figure; check your pump’s label), adds about 13 kWh a month, a little over $2. Standby dominates.

Hot tub electricity costEstimate your own monthly cost from your spa's standby watts and local temperature.

Your electricity rate matters as much as the tub

EIA projected the average US residential price at about 18¢ per kilowatt-hour for 2026, but state averages run from around 12¢ to more than 40¢. The same tub can cost three times as much to run in one state as in another. Divide your bill’s total charges by the kWh used to get your real rate. If you have a time-of-use plan, ask whether heating can be shifted to cheaper hours.

Ways to spend less

• Look after the cover. Replace it if it’s become heavy with absorbed water or no longer seals around the edge. It’s usually the biggest efficiency factor you control.
• Block the wind. A fence, screen or hedge cuts heat loss from the cover and cabinet.
• Turn it down when you’re away for more than a few days, but never off in freezing weather.
• Keep the lid on. An uncovered tub loses heat quickly through evaporation.

Keeping the water balanced matters too, since scale on the heater element makes it work harder. The hot tub chemical calculator sizes doses for small volumes, using the capacity from your manual or the hot tub volume calculator.