Running costs for a UK hot tub explained in plain English, with realistic monthly numbers and the simplest changes that actually cut the bill.
Yes, almost every modern hot tub is designed to stay on permanently. The thermostat cycles the heater on and off to hold your set temperature. Turning the unit fully off and reheating from cold every time is usually more expensive than leaving it on, not less.
On the current UK price cap, a typical four to six-person tub kept at 38C with a good cover costs roughly 50p to 90p a day in summer and 1.50 to 2.50 pounds a day in winter. That is somewhere between 25 and 75 pounds a month across the year.
Numbers swing with three things: how cold the air is, how good your cover is, and how often the jets fire. A torn or soaked cover can double your bill on its own.
If you genuinely use the tub less than once a fortnight in summer, dropping the set temperature down to about 28C between uses can save a few pounds a week. The water still needs sanitising, but the heater barely runs.
For the rest of the year, the heat loss while reheating from cold every visit usually outweighs anything you save by switching off. Cold tubs also collect biofilm faster, which costs you in chemicals.
Replace the cover when it gets heavy. A waterlogged cover is half a cover, and you can feel the difference in a single billing cycle.
Drop the temperature one degree. The energy gap between 39C and 38C is bigger than people expect because of the cooler differential to the air.
Add a thermal blanket under the main cover. A four-pound floating blanket cuts evaporation, which is where most of the heat goes.
Run the filter cycle off-peak. If you are on a time-of-use tariff, set the long filtration window for the cheap hours.
Keep the chemistry steady. Sanitiser swings make the pump work harder and the water harder to heat to a comfortable feel.
For up to two weeks yes, provided the cover is locked, the chemistry is balanced before you go, and a friend can check it after a week. Anything longer, drop it to economy mode or arrange a proper service visit.
Less than you think. The jet pump might draw 1.5 to 2kW but only for the minutes you use it. The constant heater and the long filter cycles dominate the bill.