Hot Tub Running Costs UK: Heat-Up, Standby and How to Cut Both

Quick answer: Heating a 1,000-litre hot tub from cold takes around 33kWh — about £8.70 at the current cap — and keeping it hot typically runs £30–£63 a month depending on insulation and the weather (our estimate at typical usage). Insulation, a good lid and sensible scheduling make the difference between the two ends of that range.

All costs on this page are calculated at the October–December 2026 Ofgem price cap for Direct Debit customers: 26.32p per kWh of electricity, with gas comparisons at 7.97p per kWh. Unit rates vary slightly across the 14 GB regions, so treat these as good averages and check the rate on your own bill.

The heat-up sum

Warming 1,000 litres from a 10°C fill to 38°C — a 28°C rise — takes 1,000 × 4.186 × 28 ÷ 3,600 ≈ 33 kilowatt-hours. At 26.32p per kWh that’s about £8.70, and with a typical 2kW inflatable-tub heater it takes in the region of 16 hours (add more time and a little more cost for heat escaping while it warms). Bigger rigid tubs with 3kW heaters heat faster but the energy — and cost — for the same water and temperature rise is the same physics.

Standby: what “keeping it hot” costs

These are modelled estimates — real figures depend heavily on your tub’s insulation, the set temperature, air temperature and how often the lid is off. Kept hot year-round, the range works out at roughly 1,460–2,920kWh a year, or £380–£770 at current prices, before pump and filtration cycles are added on top.

Heat-and-drain or keep it hot?

If you use the tub most days, holding temperature usually beats reheating from cold — the standing losses cost less than a full £8.69 heat-up each time. Use it once a week or less and the sums flip: one weekly heat-up (£8.69, plus a top-up before use) undercuts £47 of average standby. Many owners land in between: drop the thermostat 5–10°C between sessions, then boost before use — you pay to replace less lost heat while keeping reheat times short.

Cutting the bill: insulation first

• Keep the insulated lid on whenever the tub isn’t in use — an uncovered water surface is by far the biggest heat loser.
• Add a floating thermal blanket under the lid to cut evaporation, and an insulating ground mat beneath the tub.
• For inflatable tubs, an insulating jacket or windbreak noticeably tames the cold-weather figures.
• Drop the set-point: every degree below 38°C trims the standing loss, and 36°C still feels hot on a mild evening.
• On a time-of-use tariff, schedule the heater for off-peak hours — our Economy 7 and Economy 10 guide explains how the cheap windows work.
• Generating your own power changes the equation entirely — surplus solar generation can offset daytime tub heating.

Pumps and filtration: the forgotten line item

Heating dominates, but it isn’t the whole bill. A circulation/filtration pump at around 100W running six hours a day adds ~0.6kWh — roughly 16p a day, £4.74 a month. The powerful jets pump (1–1.5kW on many tubs) only runs during sessions: an hour of bubbles at 1.2kW is about 32p. Neither changes the verdict, but they explain why metered reality often lands a little above pure heating maths. Air-blower bubble systems on inflatable tubs are the sneaky one — they push cool air through the water, actively cooling it while they run, so every bubbly session buys you a bigger reheat afterwards.

Buying with running costs in mind

If you’re still choosing a tub, the running-cost hierarchy is simple: a rigid tub with an insulated shell, base and fitted hard cover holds heat dramatically better than an inflatable with an inch of air-filled wall — that’s the difference between the top and bottom rows of our standby table, year after year. Inflatable owners can close some of the gap with jackets, mats and thermal blankets, but buyers planning frequent winter use should weight insulation at least as heavily as jet count when comparing models.

A last word on tariffs: hot tubs are one of the few household loads big enough to make switching tariff worthwhile on their own. A tub adding 2,000kWh a year at 26.32p costs about £526; shift most of that heating into a cheaper off-peak window and the saving can run to three figures annually. If you already own an electric vehicle or storage heaters, the off-peak economics are even more likely to stack up — the tub simply joins the overnight queue.

FAQs

How much does a hot tub add to your electricity bill per month?

Typically £30–£63 a month to hold temperature at current prices, plus the cost of any full heat-ups and pump running. A well-insulated tub with the lid kept on sits at the bottom of that range; an inflatable tub in a cold garden in winter can exceed the top of it.

Is it cheaper to leave a hot tub on all the time?

Only if you use it frequently. Daily users generally do better holding temperature (or dipping a few degrees between sessions); occasional users save money heating from cold each time and switching off in between.

How can I run a hot tub more cheaply in winter?

Insulate everything — lid, sides, base — lower the set-point a couple of degrees, keep sessions planned rather than keeping it hot “just in case”, and heat during off-peak hours if your tariff has them. Winter standby costs are driven almost entirely by the temperature gap between the water and the air; see our price cap guide for what each kWh is costing you.