A 450-gallon hot tub that meets California's standby limit costs about $43.02 a month to keep at 102°F — $516 a year (2,838 kWh) at the U.S. average 18.19¢/kWh.
At 18.19¢/kWh — U.S. average, Jan–Aug 2026 (EIA).
| Water | Per year | vs 102°F |
|---|---|---|
| 98°F | $471 | −$44.83 |
| 100°F | $494 | −$22.41 |
| 102°F | $516 | — |
| 104°F | $539 | +$22.41 |
| State | ¢/kWh | kWh a year | Per year | Coldest month |
|---|---|---|---|---|
| Minnesota | 16.44 | 3,676 | $604 | $79.55 |
| Colorado | 16.8 | 3,484 | $585 | $67.66 |
| New York | 29.26 | 3,207 | $938 | $115.32 |
| Ohio | 18.81 | 3,163 | $595 | $74.48 |
| Washington | 14.42 | 3,177 | $458 | $49.26 |
| Texas | 16.03 | 2,170 | $348 | $45.08 |
| California | 32.58 | 2,571 | $838 | $89.58 |
| Arizona | 15.36 | 2,161 | $332 | $42.41 |
| Florida | 15.32 | 1,819 | $279 | $32.66 |
450^(2/3) = 58.7; × 3.75 + 40 = 260 W at a 37°F gap. Heat loss through the cover and shell scales with the gap, so each month we multiply by (102°F − average outdoor temperature) ÷ 37 and by the hours in the month.
Prices: EIA average residential rates for Jan–Aug 2026. Outdoor temperatures: NOAA Climate Prediction Center population-weighted normals.
The full method, material data and tips are on the main hot tub cost calculator page.