The short answer
A 400-gallon hot tub made since 2019, kept at 102°F under its cover, costs about $42.00 a month on average, or $503.97 a year, at the U.S. average electricity rate and climate (August 2026). Winter costs the most: about $61.64 in January. In Minnesota the same tub costs about $586.79 a year; in Florida, $250.54. Every soak with the cover off adds to this.
The same hot tub in every state
A 400-gallon hot tub made since 2019, at 102°F, at each state's electricity rate (August 2026) and monthly temperatures.
| Alabama | $30.61 | $46.08 | $367.31 | 16.33¢ |
|---|---|---|---|---|
| Alaska | $90.95 | $122.67 | $1,091.35 | 29.41¢ |
| Arizona | $24.51 | $38.62 | $294.15 | 15.05¢ |
| Arkansas | $28.65 | $43.98 | $343.82 | 14.37¢ |
| California | $60.32 | $78.54 | $723.79 | 29.75¢ |
| Colorado | $45.75 | $63.02 | $549.03 | 17.17¢ |
| Connecticut | $60.53 | $88.72 | $726.34 | 24.51¢ |
| Delaware | $41.51 | $61.99 | $498.06 | 18.70¢ |
| District of Columbia | $57.94 | $86.86 | $695.32 | 25.98¢ |
| Florida | $20.88 | $29.96 | $250.54 | 14.99¢ |
| Georgia | $30.56 | $45.24 | $366.68 | 15.90¢ |
| Hawaii | $54.33 | $65.52 | $651.98 | 47.18¢ |
| Idaho | $35.02 | $48.88 | $420.30 | 13.37¢ |
| Illinois | $47.65 | $73.75 | $571.78 | 19.32¢ |
| Indiana | $40.85 | $62.36 | $490.21 | 17.02¢ |
| Iowa | $43.86 | $68.84 | $526.32 | 17.06¢ |
| Kansas | $34.49 | $53.87 | $413.91 | 15.47¢ |
| Kentucky | $30.31 | $45.83 | $363.74 | 13.80¢ |
| Louisiana | $21.13 | $32.11 | $253.58 | 12.87¢ |
| Maine | $88.93 | $130.08 | $1,067.19 | 32.11¢ |
| Maryland | $47.73 | $71.55 | $572.75 | 21.40¢ |
| Massachusetts | $76.78 | $111.77 | $921.37 | 30.48¢ |
| Michigan | $59.57 | $88.59 | $714.86 | 22.99¢ |
| Minnesota | $48.90 | $76.06 | $586.79 | 17.20¢ |
| Mississippi | $26.07 | $39.58 | $312.83 | 14.43¢ |
| Missouri | $36.34 | $56.62 | $436.12 | 16.02¢ |
| Montana | $44.83 | $60.34 | $537.94 | 15.57¢ |
| Nebraska | $33.51 | $51.64 | $402.17 | 13.54¢ |
| Nevada | $24.79 | $37.66 | $297.47 | 12.72¢ |
| New Hampshire | $75.20 | $110.09 | $902.38 | 27.64¢ |
| New Jersey | $57.76 | $85.47 | $693.11 | 24.61¢ |
| New Mexico | $36.89 | $53.11 | $442.73 | 16.51¢ |
| New York | $71.28 | $104.84 | $855.32 | 28.65¢ |
| North Carolina | $30.32 | $44.83 | $363.84 | 14.95¢ |
| North Dakota | $39.00 | $60.08 | $468.02 | 13.31¢ |
| Ohio | $46.97 | $70.40 | $563.69 | 19.38¢ |
| Oklahoma | $29.53 | $46.32 | $354.30 | 14.82¢ |
| Oregon | $38.88 | $49.68 | $466.60 | 15.92¢ |
| Pennsylvania | $53.05 | $78.35 | $636.62 | 21.77¢ |
| Rhode Island | $69.43 | $100.62 | $833.19 | 28.18¢ |
| South Carolina | $29.38 | $43.95 | $352.52 | 15.76¢ |
| South Dakota | $40.81 | $61.83 | $489.78 | 15.15¢ |
| Tennessee | $28.01 | $42.07 | $336.12 | 13.42¢ |
| Texas | $26.24 | $40.75 | $314.88 | 15.91¢ |
| Utah | $34.97 | $49.00 | $419.63 | 13.31¢ |
| Vermont | $67.02 | $98.27 | $804.20 | 23.84¢ |
| Virginia | $38.66 | $57.14 | $463.89 | 17.64¢ |
| Washington | $36.49 | $46.69 | $437.85 | 14.63¢ |
| West Virginia | $38.18 | $56.07 | $458.16 | 16.31¢ |
| Wisconsin | $52.47 | $79.77 | $629.61 | 19.41¢ |
| Wyoming | $40.77 | $55.93 | $489.30 | 14.43¢ |
How it works
The formula
air in a month = 65°F + (cooling − heating degree days) ÷ days
watts = standby × (water − air) ÷ 37°F
cost = watts × 24 × days ÷ 1,000 × rate
Assumptions
- Standby power is the most California's appliance rules (Title 20) allow a portable electric spa to draw keeping itself hot: tested for at least 72 hours with its own cover on, water at 102°F or more and air at 60°F or less, then normalized to a 37°F gap between water and air. It includes heating, filtration and controls. Many tubs test below the limit; if you know your tub's rated standby watts, choose "I know its standby watts".
- Heat loss grows with the gap between the water and the air, so we scale the rating by each month's gap. The month's average air temperature comes from NOAA's population-weighted heating and cooling degree days for your state (1991-2020; Alaska: Anchorage; Hawaii: Honolulu). Nights are colder than the average, which this smooths over.
- Not included: soaks with the cover off, wind, a worn or waterlogged cover, refilling with cold water, and very cold snaps. Each soak can add noticeably; a bad cover can double the cost.
Worked example: a 400-gallon tub in January
Made since 2019, water at 102°F, U.S. average climate and rate
- Standby rating: 3.75 × 400^(2/3) + 40 = 244 W
- January air: about 33°F, so 244 × (102 − 33) ÷ 37 = 456 W
- 456 W × 24 h × 31 days ÷ 1,000 = 339 kWh × $0.1816 = $61.64
Ways to cut the cost
- Fix or replace the cover. A waterlogged cover is heavy and lets heat out; most last 5 to 7 years.
- Add a thermal blanket. A floating foam or bubble blanket under the cover cuts evaporation.
- Block the wind. A fence, screen or plantings around the tub reduce heat loss.
- Lower it when you're away. A few degrees lower for a week away saves without a long reheat.
- Use off-peak hours. On a time-of-use plan, set heating and filtration for cheaper hours.
Questions people ask
How much does it cost to run a hot tub per month?
A 400-gallon hot tub made since 2019, kept at 102°F with its cover on, costs about $42.00 a month on average at U.S. average prices and climate, $61.64 in January. In Minnesota, January alone is about $76.06; in Florida the costliest month is about $29.96. Soaks add to that, since heat escapes with the cover off.
Does a hot tub use a lot of electricity?
About 2,775 kWh a year for a covered 400-gallon tub sitting at temperature in an average U.S. climate, about 26% of the 10,500 kWh an average U.S. home uses in a year (EIA). Older tubs and worn covers lose more: a tub at the 2006 to 2019 limit costs about $561.61 a year against $503.97.
Is it cheaper to leave a hot tub on or turn it off?
For energy alone, letting an unused tub cool saves a little: a cooler tub loses heat more slowly, and reheating only puts back what was lost. But reheating takes many hours, and in freezing weather a tub that's off can freeze and crack its pipes. For daily use, keep it at temperature; for a week or more away in mild weather, lower the setpoint by 10 to 15°F; in winter, leave it on or use the freeze-protection mode. On a time-of-use plan, heating at off-peak hours saves more.
How much does lowering the temperature save?
Heat loss follows the gap between the water and the air. At U.S. average conditions, keeping the water at 98°F instead of 102°F cuts the yearly cost from $503.97 to $462.05.
How do I make my hot tub cheaper to run?
A tight, dry cover matters most: a waterlogged or cracked cover lets most of the heat out. Keep the cover clipped down, add a floating thermal blanket under it, block the wind, and run the filtration cycles off-peak if your utility has time-of-use rates.