No maker on our site publishes a measured yearly running cost, and we have not run any of these tubs ourselves. What we can do is work from the numbers the makers do publish: how much water each tub holds, what its wall is made of and, where listed, the heater power. This guide shows every sum so you can redo it with your own tariff.
Our assumption: electricity at 25p per kWh. Your price will differ by supplier, region and tariff. Swap in the unit rate from your bill.
Two costs, two different drivers
Running a hot tub costs you in two ways:
- The first heat. Warming the water from tap temperature. This depends on how much water the tub holds.
- Keeping it hot. Replacing the heat that leaks out. This depends on the wall, the lid and the weather.
Notice what is missing: the heater's wattage. A bigger heater warms the water faster, but it does not use less energy to do it. We come back to that below.
Cost 1: the first heat, tub by tub
Heating 1 litre of water by 1 °C takes about 1.16 Wh. From 15 °C tap water to 38 °C is 23 degrees. So:
litres x 1.16 x 23 / 1,000 = kWh, then kWh x £0.25 = cost.
Here it is for every tub where the maker publishes the volume:
| Hot tub | Water | Energy | Cost at 25p |
|---|---|---|---|
| Wave Tahoe 4 | 650 litres | 17.3 kWh | £4.34 |
| Lay-Z-Spa Boracay | 669 litres | 17.8 kWh | £4.46 |
| Intex PureSpa Onyx Octagon | 795 litres | 21.2 kWh | £5.30 |
| Wave Atlantic 6 | 800 litres | 21.3 kWh | £5.34 |
| Arebos Barcelona 6 | 910 litres | 24.3 kWh | £6.07 |
| Nordivale Square 4-6 | 910 litres | 24.3 kWh | £6.07 |
| MSpa Denver | 970 litres | 25.9 kWh | £6.47 |
| Aoxun 208 cm | 1,000 litres | 26.7 kWh | £6.67 |
| Intex PureSpa Jet & Bubble Deluxe | 1,098 litres | 29.3 kWh | £7.32 |
| Wave Garda 6 | 1,100 litres | 29.3 kWh | £7.34 |
| MSpa Tuscany | 1,100 litres | 29.3 kWh | £7.34 |
| MSpa Aero Plus | 1,150 litres | 30.7 kWh | £7.67 |
| Intex PureSpa Bubble 8 | 1,340 litres | 35.8 kWh | £8.94 |
The other tubs on our site do not have a published volume. The real first heat costs more than these figures, because the tub loses heat to the air while it warms up.
You only pay the first heat when you fill or refill. If you change the water every month or two, it is a small part of the year's bill.
Cost 2: keeping it hot
This is the big one, and it depends on how fast heat leaks out. Nobody on our site publishes a measured heat loss figure, so we rank the walls the way our score does, using the makers' own claims:
| Wall | Maker's claim | Our insulation points |
|---|---|---|
| Foam core (Lay-Z-Spa ThermaCore, Wave WaveEco) | up to 60 % more efficient | 2 of 2 |
| Rigid frame with TempXcel layer (MSpa Denver, Aero Plus) | none published | 2 of 2 |
| Rigid frame, no extra layer | none published | 1.5 of 2 |
| Insulated liner or drop-stitch (Lay-Z-Spa EnergySense, Helsinki) | up to 40 % (EnergySense) | 1 of 2 |
| Plain air wall | none | 0.5 of 2 |
The only per-day figure on our site comes from Wave: about £2 a day to hold 40 °C in the Tahoe 4 and Garda 6. Wave does not say what unit price or weather it assumed. At our 25p, £2 would buy 8 kWh. Treat it as a maker's ballpark, not a promise.
Why heater watts do not decide the bill
Only three brands on our site publish the heater power: Intex (2,200 W), Arebos and Aoxun (1,800 W each). Here is what those figures mean:
- 2,200 W for one hour = 2.2 kWh = 55p at 25p.
- 1,800 W for one hour = 1.8 kWh = 45p.
The 1,800 W heater costs less per hour, but it has to run longer to deliver the same heat. Warming the Aoxun's 1,000 litres by 23 °C takes 26.7 kWh either way. At 1,800 W that is at least 14.8 hours; Aoxun itself quotes 1 to 2 °C an hour. The cost is the same 26.7 kWh, about £6.67.
So a lower wattage is not a cheaper tub. Over a year, the wall and the lid decide how many kWh the heater has to replace.
The jets add a bit
Pumps for bubbles and water jets also use power, and the cold air from a bubble blower cools the water. From the published figures:
- Arebos blower, 600 W for 30 minutes = 0.3 kWh = 7.5p
- Intex Jet & Bubble Deluxe jet pump, 1,000 W for 30 minutes = 0.5 kWh = 12.5p
- MSpa Denver or Aero Plus hydrotherapy pump, 1,100 W for 30 minutes = 0.55 kWh = about 14p
Small next to heating, but they add up if you use the tub every day.
So which tub is cheapest to run?
Put the two drivers together: little water and a foam wall.
- Wave Tahoe 4. The smallest volume on our site (650 litres) and a 6-inch foam core. Cheapest first heat and the best wall. It costs £1,010 and is sold for 4 people.
- Lay-Z-Spa Carrara. ThermaCore foam, 170 cm across, heater in the wall, £725. Lay-Z-Spa does not publish its volume, but at 170 cm it is among the smallest tubs here.
- Lay-Z-Spa Stockholm. ThermaCore foam, 164 cm square, £1,000.
- Lay-Z-Spa Toronto. Foam wall, sold for 5 to 7, £700. More water than the three above, but our highest scoring tub overall.
On a smaller budget, the Lay-Z-Spa Boracay holds just 669 litres for £390, so its first heat is cheap. Its DuraPlus wall has no insulating layer, though, so it loses more heat once warm. Use it mainly in the warmer months.
Quick answers
Is a small tub always cheaper to run? Less water means a cheaper first heat and less surface to lose heat from. A small plain inflatable can still cost more over a winter than a bigger foam tub.
What tariff should I use? Your own unit rate. If you have a cheaper night rate and app control, heat at night.
More ways to cut the bill: hot tub energy saving tips, hot tub covers and heat loss, how long a hot tub takes to heat and hot tub running costs.
