How Much Does a Hot Tub Cost to Run Per Month?

The honest range for a hard-shell hot tub is $20 to $60 per month in mild weather and $50 to $120 in a cold winter, and the spread between those numbers is mostly your climate, your electric rate, and your cover. Here is the math so you can place yourself in the range.

Where the electricity goes

• Holding temperature (60 to 75 percent of the bill). A hot tub sits 30 to 70°F hotter than the air around it, constantly leaking heat through the cover, shell, and plumbing. The hotter the gap, the faster the leak, which is why winter costs double.
• Heating after use and refills. Every soak with the lid open dumps heat (evaporation, the same physics as the pool evaporation calculator, just hotter water and a bigger gap), and every quarterly refill reheats 300 to 450 gallons from tap-cold.
• Circulation and jets. The circulation pump is small but runs many hours; jet pumps are 1.5 to 3 kW but only while you soak.

The back-of-envelope formula

At the US average of about 15 cents/kWh that is $14 to $23 per month in mild months and $32 to $54 in cold ones for a well-insulated 400 gallon tub. In high-rate states (California ~32 cents, Massachusetts ~31 cents) double those figures; in cheap-power states (Idaho, Washington ~11 to 12 cents) trim a quarter off. Your electric rate matters as much as your climate, the state-by-state rates in the heating cost calculator apply directly.

A worked example: 400 gallons in a cold snap

1. Water at 102°F, garage-free backyard air at 30°F: a 72°F gap.
2. A quality tub with a good cover loses roughly 250 to 400 watts continuously at that gap → 6 to 10 kWh/day.
3. At 15 cents/kWh: $27 to $45 for the month, before any soaking.
4. Each hour-long soak with the lid off adds roughly 1.5 to 3 kWh (evaporative loss plus jet pumps): a nightly soaker adds $10 to $15 monthly.

The five cheapest ways to cut the bill

1. Replace a waterlogged cover. The cover is the entire ballgame, an old foam cover soaked with water conducts heat many times faster than a dry one. If it is heavy to lift, it is expensive to own. $300 to $500, pays back in one to two winters.
2. Add a floating thermal blanket under the cover. $30 to $60, cuts evaporation at the water surface, the same 95 percent evaporation logic as a solar pool cover, scaled down.
3. Time heating to off-peak rates if your utility has them, most tubs hold temperature well enough to coast through peak hours a few degrees lower.
4. Windbreak. Wind strips heat from the cover and shell; a fence panel or placement against the house measurably lowers winter draw.
5. Keep the water balanced. Scale on the heater element makes it work longer for the same heat, the same alkalinity-first balancing order applies to spas, just with faster drift because the volume is small.

Total cost of ownership, honestly

Beyond electricity: chemicals $10 to $20 per month, a refill every 3 to 4 months (a few dollars of water, plus reheat), a filter cartridge or two per year, and the cover every 5 to 7 years. All-in, a maintained hard-shell tub runs $40 to $90 per month averaged over the year in most of the US, less than a family streaming bundle-plus-gym combo, but only if the cover is good and the setpoint strategy matches how often you actually soak.