Hot tub electricity cost calculator
Example estimate: about $46 a month, using 272 kilowatt-hours (kWh) at $0.17 per kWh. Enter your own numbers below to see your monthly cost and where it goes.
This example holds 400 US gallons at 100 °F, with 50 °F air and a good cover with full foam. It uses a 200 W pump for 8 hours a day and no full reheats. The model assumes 11 W of heat loss per °C and 100% electric heater efficiency. Your weather, cover and rate will change the estimate.
On the spec sheet. Typical home tubs hold 300–500 US gallons.
Per kWh, from your bill.
What you keep it set to. Every degree lower saves real money.
Your yearly average, not today's. Heat loss tracks this gap.
A low-speed circ pump is 40–200 W. A two-speed on low is more.
Many tubs ship on 24/7 but filter fine on 6–12 hours.
Set by the choice above. Override it if you have measured yours.
Drain-and-refills or holidays when you let it go cold. Usually 0.
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Fill in the fields to see your answer.
- Per day—
- Per month—
- Per year—
- kWh per month—
What if you changed one thing?
Each row changes a single setting and leaves everything else as you entered it.
What this assumes
- Standby loss is a lumped figure in watts per °C of difference between water and air, set by the insulation preset. It is an empirical shorthand, not a surface-by-surface heat model.
- Electric resistance heating is ~100% efficient — essentially all the energy ends up in the water. A heat pump would beat this by 3–5×.
- Your outdoor average drives the bill. Using a summer figure will understate winter badly. The annual mean is the honest input.
- Wind and cover condition are not modelled. An exposed tub in a windy yard can lose noticeably more than this.
How this calculation works
- Standby loss
- Circulation pump
- Reheating
- Monthly cost
kWh/month = (W/°C × ΔT × 730) ÷ 1000 + (pump W × hrs × 30.4) ÷ 1000 + reheats
Standby loss is the big one: a lumped figure in watts lost for every °C between the water and the air, running every hour of the month. Circulation is simply pump watts times hours. Reheating uses the specific heat capacity of water, 4.186 kJ per kg per °C.
| Cover | Loss | At 40 °F outside | Per month |
|---|---|---|---|
| New hard cover, dense foam | 7 W/°C | 230 W | ~$29 |
| Good cover, full-foam shell | 11 W/°C | 360 W | ~$45 |
| Standard, partial foam | 17 W/°C | 560 W | ~$70 |
| Thin or waterlogged | 26 W/°C | 860 W | ~$107 |
Where the money actually goes
For most tubs, standby loss — simply holding the water at temperature while nobody is in it — is the largest line by a wide margin, often 60 to 80 percent of the bill. That is why cover condition matters more than almost anything else, and why the "how often do you use it" question people expect to be decisive barely moves the total.
The circulation pump is the quiet second. A 200 W pump left running around the clock uses about 146 kWh a month on its own — comparable to a refrigerator running continuously. Cutting it to eight hours a day usually costs nothing in water quality on a modern tub.
The three changes that actually help
- Replace a tired cover. Foam that has absorbed water insulates poorly and is heavy — if you struggle to lift it, it is costing you.
- Drop the setpoint two degrees. Heat loss is proportional to the water-to-air gap, so this is a straight percentage off the standby line.
- Put the pump on a schedule. Check the manual for the minimum turnover your filter needs, then run that and no more.
Try each one above. The scenario rows price them against your numbers.
For the full picture, read where a hot tub's electricity actually goes. For cold months, see how much a hot tub costs in winter.
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