Hot Tub Running Cost Calculator UK

It depends heavily on tub type and how you use it. Checkatrade's 2026 data puts inflatable spas at roughly £35-60 a month and hard-shell tubs at £50-150 a month, with the wide hard-shell range reflecting the difference between a small 13A plug-in tub and a larger hardwired one. This calculator narrows that down using your specific tub type, usage pattern, season and electricity price.

For most people, cheaper to leave it running at temperature if you use it three or more times a week. Lay-Z-Spa's own guidance states that reheating water from cold uses more energy overall than maintaining a steady temperature, because the heater has to work harder to raise the temperature quickly than it does to make up for gradual heat loss. This calculator's worked example shows a £27.60/month difference for one tub and season combination.

The Lay-Z-Spa heater and pump unit draws a combined 2050W (2.05kW) when actively heating. It doesn't run at that rate all day - this calculator estimates the actual duty cycle (roughly 12-27% of the day depending on usage and season) to convert that wattage into a daily kWh and cost figure.

Generally yes, in absolute terms. A larger hardwired tub on a 32A supply typically draws 6-7.5kW versus 2-3kW for a small 13A tub, so even though a larger, better-insulated tub can run at a slightly lower duty cycle, the higher power draw usually still means a higher total cost - this calculator's default comparison shows a large hard-shell tub costing roughly two to three times more per month than an inflatable spa under the same usage pattern.

Yes. Steam & Oak's 2026 data for a well-insulated 6-person tub shows roughly £20-35 a month in summer rising to £50-70 a month in winter - a 1.5 to 1.8x increase - because a larger temperature gap between the water and the cold outside air means the tub loses heat faster and the heater has to run more often to compensate.

The default is 26.11p/kWh, the Ofgem Direct Debit price cap unit rate for 1 July-30 September 2026. The cap is reviewed roughly every three months, so replace this with your own tariff's unit rate (found on a recent bill) for an accurate result, especially if you're on a fixed-rate tariff rather than the standard variable Direct Debit cap.

At the default inflatable-spa, kept-warm, summer scenario and the current Ofgem rate, this calculator estimates around £577 a year - but that's a single-season figure. A full year mixing summer, spring/autumn and winter conditions, or a hard-shell tub, will land closer to Checkatrade's broader £760-£1,270 a year total running-cost estimate, which also includes chemicals, water and servicing beyond electricity alone.

Some, but less than the heater. The "used most days, jets used often" option in this calculator applies a 15% uplift to the duty cycle to account for the circulation pump and jet pump running beyond active heating; C-Lec Electrical notes a circulation pump alone typically draws around 1.5kW when it is running, separately from the heater.

Because heater run-time isn't a fixed daily schedule - a well-insulated tub holding a steady temperature might only need the heater for short bursts spread across the day, while a poorly insulated one runs almost continuously. A duty cycle (the percentage of the day the unit draws power) captures that without requiring you to know exactly how many hours your specific heater ran, which almost nobody tracks.

Usually, but not always. This calculator's baseline duty cycles put a small hard-shell tub only slightly above an inflatable spa on a like-for-like usage pattern, since better insulation on some hard-shell models partly offsets their higher power draw. A large hardwired tub is consistently the most expensive of the three in every scenario this calculator models, mainly because of its substantially higher heater wattage.

Electricity standing charges, water, chemicals (chlorine or bromine, pH balancers), filter replacements and servicing are not included - this figure covers only the electricity used by the heater and pump. Checkatrade's £760-£1,270/year figure is a better guide to total annual cost of ownership including those extras.

Yes. A well-fitted, undamaged thermal cover is the single biggest lever, since heat loss through an uncovered or worn-out cover surface is usually the largest source of energy waste; keeping the tub covered whenever it's not in use, avoiding letting the water fully cool between uses if you use it three or more times a week, and lowering the target temperature by even 1-2 degrees can all reduce the duty cycle this calculator applies.

Yes, as a general estimate. The inflatable-spa preset uses the Lay-Z-Spa 2.05kW figure as a representative baseline since Bestway is the dominant UK inflatable-spa brand, but most inflatable spa heater+pump units from other manufacturers draw a broadly similar 1.5-2.5kW, so the estimate should be in the right range even for a different brand.

It's a planning estimate, not a guarantee. Real-world running costs vary with your tub's specific insulation and cover condition, your target temperature, local weather, and how consistently you use it - factors this calculator cannot see. For an exact figure, compare a week of smart meter readings with the tub running normally against a week with it switched off, if that's practical for your household.

It depends on how long it's off and how cold it gets. For a short break (a few days), leaving the heater on a lower "away" or economy setting if your tub has one is usually cheaper than a full reheat from cold on your return. For an extended period of disuse (weeks or more), fully draining and switching off will save more than any running mode, but you'll need to refill and reheat from scratch when you restart it, which uses significantly more energy than any single day modelled by this calculator.