How this calculator works
The cost of running a hot tub is the energy it uses multiplied by the price of electricity. The difficulty is the power figure: the nameplate rating assumes the heater, pumps and blower are all running, but a tub cycles. In a cold month the heater runs more, in a warm one less, and a cover makes a large difference. Entering an average draw over a full day, measured with a plug-in meter, gives a far better estimate than using the nameplate. The daily energy is that average power times the hours it is connected and running, and the annual figure assumes the same pattern all year.
Formula
kWh per day = average watts x hours per day / 1,000. energy for a period = kWh per day x days. cost = energy x price per kWh. annual cost = kWh per day x 365 x price.
Worked example
A tub drawing an average of 1,500 W for 6 hours a day uses 9 kWh a day. At 15 cents per kWh that is $1.35 a day, $40.50 for 30 days and about $492.75 for a year.
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Frequently asked questions
Why is the average draw so much lower than the heater rating?
A 5 kW heater that runs for a third of the day averages about 1.7 kW. Add the circulation pump and the average for the whole tub lands in the low kilowatts rather than the full nameplate figure.
How much does a cover save?
A fitted cover reduces evaporation and heat loss, which are the two largest losses for an outdoor tub. Many owners report the heater running far less in winter with a good cover; measure before and after to see the effect on your bill.
Does the temperature setting matter?
Yes. Every degree you lower the set point reduces the difference between the water and the air, and therefore the heat loss. Lowering it while away is one of the simplest savings.
Is this the whole cost of owning a hot tub?
No. It covers electricity only. Chemicals, filters, water, servicing and repairs are separate, and in a cold climate the heater fraction is higher than in a mild one.