Hot Tub Running Cost Calculator
Hot tubs are notorious energy users, mostly from the heater keeping water warm. This calculator estimates the monthly and yearly running cost.
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How it works
Daily energy = heater power × heating hours per day. Monthly energy = daily × 30.4. Monthly cost = energy × rate; yearly = monthly × 12. A good cover, lower temperature and off-peak heating are the biggest savings.
Worked example, step by step
Take the defaults: a 6 kW heater that runs about 3 hours a day to hold temperature, at $0.17/kWh.
Daily energy = 6 kW × 3 hours = 18 kWh.
Monthly energy = 18 kWh × 30.4 days = 547 kWh.
Monthly cost = 547 kWh × $0.17 = about $93.
Yearly cost = $93 × 12 = roughly $1,116.
The heating hours per day is the number that swings this the most, and it is driven almost entirely by how well the tub holds heat — a well-insulated tub with a good cover in mild weather might only need 1–2 hours of heating a day, while a poorly-covered tub in winter can need 5+ hours, more than doubling the cost.
How to actually cut a hot tub's running cost
A hot tub's bill is almost all about heat loss — the heater only works to replace heat that escapes, so cutting losses cuts the bill directly.
The cover is the single biggest factor. A well-fitting, thick, undamaged insulated cover can dramatically reduce how many hours the heater runs. A waterlogged or ill-fitting cover is the most common reason for a shocking hot tub bill.
Temperature setting compounds fast: every degree you lower the set temperature reduces the heat-loss gradient, so dropping from 40°C to 38°C saves more than it sounds. Many people keep a tub hotter than they actually use it at.
Off-peak heating helps if you are on a time-of-use tariff — heating the water during cheap overnight hours and coasting through peak times can meaningfully lower the effective rate. Our time-of-use savings calculator shows how much that shift is worth.
Finally, for a tub used only occasionally, dropping the temperature between uses saves more than holding it hot — but for near-daily use, holding temperature is usually more efficient than fully cooling and reheating a large volume of water each time.
Frequently asked questions
Why is my hot tub so expensive to run?
Most cost comes from the heater working to hold temperature, especially in cold weather or with a poor cover. Pumps and jets add a little more.
How can I cut hot tub costs?
Use a well-fitting insulated cover, lower the set temperature a couple of degrees, and heat during off-peak hours if you have time-of-use pricing.
Should I turn it off between uses?
For infrequent use, lowering the temperature usually saves more than fully cooling and reheating. For daily use, holding temperature is normal.
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