Short answer: most inflatable and foam hot tubs in the UK cost somewhere between roughly £18 and £50 a month to run — but that spread is huge for a reason. What you actually pay depends on the season, your cover, how often you use it, the temperature you hold, and above all the type of heater doing the work. This guide breaks down each of those, using real 2026 figures, and shows where the savings genuinely are (and where they aren't).
Almost all the running cost of a hot tub is electricity to make heat: heating the water up in the first place, then topping it up to replace heat lost to the air, the ground and evaporation. The pump and filter draw a little, but heating is the number that matters.
UK electricity is currently capped at about 26p per kWh (Ofgem price cap, 1 Jul–30 Sep 2026, direct debit including VAT; plus a 57.19p/day standing charge you pay anyway). That cap moves every quarter — it was 27.69p in Jan–Mar and 24.67p in Apr–Jun 2026 — so treat any running-cost figure as a snapshot, not a fixed law.
Lay-Z-Spa, one of the biggest inflatable brands, publishes its own running-cost estimate:
(Source: Lay-Z-Spa's own figures.) These are a useful ballpark, but treat them as the optimistic end. Manufacturer estimates tend to assume a decent cover, sensible use and milder weather. In a cold snap, with the lid coming off twice a day and a thin cover, real bills climb toward — and past — the top of that range. Your model, your tub size and your winter will move the number more than any brochure can.
This is the biggest lever. A tub sitting at 38°C loses heat far faster on a 2°C January night than a 20°C July evening, so the heater runs more to keep up. The same tub can easily cost two to three times as much in deep winter as in summer.
Most heat escapes off the top of the water. A well-fitting, thick, undamaged insulated cover — kept on whenever you're not in — is the single cheapest saving available. A soggy, thin or ill-fitting lid quietly wastes money every hour. A ground mat underneath and a wind break around the tub help too.
Every time the cover comes off, heat pours out and the heater has to recover it. Long sessions, frequent dips and lots of splashing (evaporation is a real heat loss) all add up. Fewer, longer soaks generally cost less than lots of short ones.
Holding the water at 40°C costs more than holding it at 37°C, every single day. If you use the tub at weekends, dropping the maintenance temperature during the week — or timing heat-ups so the water is ready when you want it, not 24/7 — cuts the bill noticeably.
This is the factor most people never think about, and it's the one with the most headroom.
The heater built into nearly every inflatable and foam hot tub is a resistive electric element, roughly 1.5–3 kW (for example, the Wave Atlantic uses an 1800 W element; Lay-Z-Spa models are typically around 1.5–2 kW). Resistive heating is about 100% efficient — one unit of electricity in, one unit of heat out. In efficiency terms that's a COP of 1. It can't do better; physics won't allow it.
An air-source heat pump doesn't make heat, it moves it — pulling warmth out of the outside air and pumping it into the water. That lets it deliver several units of heat per unit of electricity. A typical hot-tub heat pump runs at a COP of about 3–5 (loosely, "350% efficient"), meaning it uses roughly a third to a fifth of the electricity of a resistive heater for the same heat.
The honest caveat: that efficiency isn't constant. Heat pumps work harder when there's less warmth in the air to harvest, so COP falls in the cold. A unit running near COP 4 on a mild 15°C day can drop to roughly COP 2–2.5 near freezing. So think of it as ~COP 3–5 across the milder months and a more modest ~COP 2–3 in winter — still comfortably better than resistive, but we won't pretend it's four-times cheaper in January. Anyone quoting a single fixed annual saving is guessing.
| Heater type | Typical efficiency (COP) | Electricity used for the same heat |
|---|---|---|
| Built-in resistive element | 1 (all year) | 100% (the baseline) |
| Air-source heat pump (milder months) | ~3–5 | Roughly a fifth to a third |
| Air-source heat pump (cold winter) | ~2–3 | Roughly a third to a half |
COP = coefficient of performance: units of heat delivered per unit of electricity used. Higher is better.
Most advice on running costs ends with a list of things you have to remember to do. Our full Eco Conversion Kit does the remembering. It's a self-contained energy system — a 610W bifacial solar panel on a ground frame, a smart power box with a built-in battery, an inverter-driven heat pump, and a smart switch box that decides where the next unit of energy comes from.
Every time your tub needs heat, the system works down a simple order: free solar first, then stored battery, then cheap off-peak overnight, and mains only when there's genuinely no better option. You don't flick anything or watch the clock — it just quietly buys the cheapest, greenest energy available at that moment.
Because it's harvesting and storing your own power, the biggest driver of a hot tub bill — heating on full-price mains — becomes the exception rather than the rule. See what that looks like for your tub and tariff with our savings calculator. Hot water needn't cost the earth.
Honestly, it depends on your tub, your usage, the season and your tariff — which is exactly why we won't print a single made-up figure here. We run real hot-tub kit in the UK and monitor its actual performance, and even we treat these numbers conservatively. Instead of a guess, try our savings calculator for a personalised estimate based on your own setup. Hot water needn't cost the earth — but the right number for you is worth working out properly.
Ready to talk specifics? Get in touch or reserve a kit and we'll help you work out whether it stacks up for your tub.
Roughly £18–£50 a month for a typical inflatable or foam tub (Lay-Z-Spa's own figures), but expect the higher end in winter and with heavy use. Your cover, temperature setting, usage and tariff all move the number. Use our savings calculator for an estimate tailored to you.
For the same heat, yes — a heat pump typically uses a third to a fifth of the electricity of a resistive element, because it moves heat rather than making it. The gap narrows in cold weather (winter COP is nearer 2–3 than 4–5), but it stays meaningfully cheaper.
Not always. Reheating from cold takes a lot of energy, so for regular users it's usually cheaper to hold a lower maintenance temperature with a good cover than to cool right down and reheat. For occasional use, timed heat-ups on an off-peak tariff work well.
Get a personalised running-cost and payback estimate for your hot tub in under a minute.