Show the formula and working
This hot tub running cost calculator works out what an inflatable or hard shell hot tub costs to run per day, per week, per month and per year, for owners in the UK, Ireland and the rest of Europe. It adds the heater, the pump and jets, and the energy to heat each fresh fill of water, then shows the total in pounds or euros with the working.
Quick answer: A hot tub running cost calculator multiplies the heater and pump power in kW by their hours and your price per kWh, then adds the cost of heating each refill. A 3 kW heater running 3 hours a day plus an 800 W pump for 1 hour uses 9.8 kWh, about £2.58 a day at 26.32p per kWh.
What Is a Hot Tub Running Cost Calculator?
A hot tub running cost calculator is a tool that estimates the electricity a hot tub uses to keep its water hot and filtered, and what that electricity costs. In plain words: heater kW x heater hours, plus pump kW x pump hours, gives the daily kWh. Multiply by your unit rate for the daily cost, then add the energy to heat each new fill from cold.
The refill part uses the heat needed to warm water: litres x 4.18 x temperature rise in °C, divided by 3,600, gives kWh. The 4.18 comes from the specific heat of water, which the Wikipedia specific heat capacity article gives as about 4,185 J per kg per kelvin. Heating 1,000 litres from 10 °C to 38 °C takes about 32.5 kWh.
How Do You Use the Hot Tub Running Cost Calculator?
- Enter the Heater power in kW from the manual or spec plate.
- Enter the Heater hours per day. This is the time the heater actually runs to hold temperature, which a smart meter or the tub’s display can show. It rises in cold weather.
- Enter the Pump and jets power and the Pump and jets hours per day.
- Set the Days running per year. Lower it if you empty the tub for winter.
- Enter the Water volume, Fill water temperature, Set temperature and Refills per year so the cost of heating fresh water is included.
- Check the Electricity unit rate against your bill, and switch to euros if you pay in cents.
- Read the monthly, weekly and yearly cost, then open “Show the formula and working” to check each step.
How Much Does a Hot Tub Cost to Run per Week?
A hot tub using 10 kWh a day costs about £18.42 a week at 26.32p per kWh, the average unit rate under the Ofgem price cap for October to December 2026. Daily use depends mostly on insulation, the lid, the weather and how often you use it, so the table shows a range rather than one figure.
| Energy per day | Cost per day | Cost per week | Cost per month (average) | Cost per year |
|---|---|---|---|---|
| 5 kWh | £1.32 | £9.21 | £40.03 | £480.34 |
| 8 kWh | £2.11 | £14.74 | £64.05 | £768.54 |
| 10 kWh | £2.63 | £18.42 | £80.06 | £960.68 |
| 15 kWh | £3.95 | £27.64 | £120.08 | £1,441.02 |
| 20 kWh | £5.26 | £36.85 | £160.11 | £1,921.36 |
Costs use 26.32p per kWh and 365 days, and leave out refills. The daily energy figures are examples. Read your own from a smart meter by noting the reading at the same time on two days with the rest of the house as quiet as possible.
Are Inflatable Hot Tubs Cheaper to Run?
Inflatable hot tubs are usually more expensive to run than well insulated hard shell tubs, because their thin walls and lids lose heat faster, so the heater runs for more hours. They are cheaper to buy and hold less water, which makes each refill cheaper to heat. In winter an inflatable tub can use several times the energy it uses in summer, so enter higher heater hours for cold months.
How Long Does a Hot Tub Take to Heat Up?
A 1,000 litre hot tub with a 3 kW heater takes roughly 11 hours to heat from 10 °C to 38 °C, if no heat were lost on the way. In practice it takes longer, especially outdoors in winter with the lid off, because the tub keeps losing heat while it warms. Keep the lid on while it heats to shorten the time.
How Can You Cut Hot Tub Running Costs?
The biggest saving is to keep a well fitting insulated lid on whenever the tub is not in use, because much of the heat escapes from the open water surface. Other steps that help:
- Shelter the tub from wind and add an insulated floor mat under inflatable models.
- Lower the set temperature by 1 °C or 2 °C between uses rather than switching off fully and reheating from cold.
- Run filtration and heating on cheaper off peak hours if your tariff allows it. The Economy 7 calculator shows the difference.
- Use daytime solar power if you have panels. The solar panel calculator estimates how much a system could generate.
Plug and play tubs run from a 13 A socket, while larger hard shell tubs usually need a dedicated hardwired supply with RCD protection, which must be installed by a qualified electrician. Keep the water treated and changed as the maker advises. The HSE notes that spa pools and hot tubs are a recognised source of legionella if poorly managed.
Worked Example: A Hot Tub
Example: a 1,000 litre hot tub has a 3 kW heater. A smart meter suggests the heater runs about 3 hours a day, and the 800 W pump and jets run 1 hour a day. It runs all year at 38 °C, it is refilled 4 times a year with 10 °C water, and the unit rate is 26.32p per kWh.
- Daily energy: 3 kW x 3 h + 0.8 kW x 1 h = 9.8 kWh, costing £2.58 a day
- Weekly cost without refills: £2.58 x 7 = £18.06
- Each refill: 1,000 L x 4.18 x 28 °C / 3,600 = 32.5 kWh, costing £8.56 and taking about 10 h 50 min at 3 kW
- Yearly energy: 9.8 kWh x 365 + 32.5 kWh x 4 = 3,707 kWh
- Yearly cost: 3,707 kWh x 26.32p = £975.69, or £81.31 a month on average
A friend in Germany with the same tub and an example rate of 35c per kWh would pay about €3.43 a day, plus about €11.38 to heat each refill. More household energy tools are in our energy bill calculators hub.
Hot Tub Running Cost Calculator FAQs
How much does a 3 kW hot tub heater cost per hour?
A 3 kW heater uses 3 kWh an hour, which costs about 79p at 26.32p per kWh. It only draws that while it is actually heating. Once the water is at temperature, the thermostat runs it for short spells to replace lost heat.
Is it cheaper to leave a hot tub on all the time?
For regular use, usually yes. Reheating 1,000 litres from cold takes about 32.5 kWh, so switching off between weekly uses can cost more than holding temperature with a good lid. If you will not use it for weeks, lowering the temperature or emptying it saves more.
Does a hot tub cost more to run in winter?
Yes. Colder air and colder fill water mean the heater runs for longer to hold the same temperature. Run the calculator twice, with summer and winter heater hours, to see the range for your tub.
How do I measure my hot tub’s electricity use?
Note your smart meter or electricity meter reading at the same time on two days and subtract, ideally on days when other use is similar. Some tubs show energy use on the control panel. A plug in energy monitor works for 13 A plug and play tubs.
What temperature should a hot tub be?
Most people use 36 °C to 38 °C, and most hot tubs have a maximum setting of 40 °C. Each degree lower reduces heat loss slightly. Children and pregnant women should follow the maker’s guidance on temperature and time.
Does the standing charge count towards hot tub costs?
No. The daily standing charge is paid whether or not the hot tub runs, so it is not part of its running cost. This calculator uses only the unit rate for the extra kWh the tub uses.
Checked October 2026. Sources: Energy price cap unit rates and standing charges (Ofgem), Spa pools and legionella (HSE), Specific heat capacity (Wikipedia).