A home cold plunge in the UK typically costs somewhere between well under £1 and a few pounds a day to run, depending mainly on the chiller's power, how much of the day it actually runs and your electricity tariff. At the Ofgem price cap rate for 1 October to 31 December 2026, a chiller drawing 1kW costs about 26p for every hour it runs. The worked examples below show how to estimate your own costs.
All figures here are estimates. Real costs vary with ambient temperature, insulation, how often the cover is on and the tariff you pay. For more on choosing a plunge, see our cold plunge buying guide.
The electricity price we have used
Ofgem, the energy regulator for Great Britain, sets a price cap on standard variable tariffs and reviews it every three months. For 1 October to 31 December 2026, Ofgem gives an average electricity unit rate of 26.32p per kWh with a daily standing charge of 54.83p, for customers paying by Direct Debit. These are averages across Great Britain. Your rate depends on your region, payment method and whether you are on a fixed or time-of-use tariff, so check your latest bill and swap in your own figure. You pay the standing charge whether or not you own a plunge, so the examples below leave it out.
How to work out the running cost
The calculation has three parts:
- Rated power (kW). The electrical input printed in the specification, not the cooling capacity. A chiller moves heat rather than creating cold, so its cooling capacity is often several times its electrical input. Our guide to cold plunge chillers explains the difference.
- Duty cycle. Once the water reaches its set temperature, the chiller switches on and off to replace heat that leaks back in. The duty cycle is the share of the day it is actually running. It is the biggest unknown, and it changes with the weather.
- Unit rate. The price you pay per kWh.
The formula is: rated power (kW) x 24 hours x duty cycle x unit rate = daily cost.
Rated power is generally a maximum, so a chiller may draw less than its rated figure for part of the time it runs. That makes these examples cautious rather than optimistic.
Worked examples
Each example uses 26.32p per kWh, a 30-day month and the duty cycle stated. The duty cycles are illustrative assumptions, not measurements of any particular unit.
Example 1: a small chiller rated at 0.4kW
- Assumption: running 30% of the day, for example a covered tub in a cool garage in spring.
- 0.4kW x 24 hours x 0.30 = 2.88kWh per day.
- 2.88kWh x 26.32p = about 76p per day, or about £23 per month.
- At a 50% duty cycle, for example in warmer weather, that rises to 4.8kWh, about £1.26 per day or £38 per month.
Example 2: a chiller rated at 1.02kW
The ThermoX Drop bath chiller has a rated power supply of 1.02kW, so we have used that figure.
- At a 25% duty cycle: 1.02kW x 24 x 0.25 = 6.12kWh per day, about £1.61 per day or £48 per month.
- At a 50% duty cycle: 12.24kWh per day, about £3.22 per day or £97 per month.
- Theoretical ceiling if it ran non-stop all day: 24.48kWh, about £6.44 per day. Once the water is at temperature, a chiller should not need to run continuously in normal conditions.
Example 3: cooling only when you plunge
If you use a bath chiller, you may fill the bath, cool it, plunge and drain, rather than holding a full tub at temperature all week. In that case, think per session.
- Assumption: the chiller runs at its rated 1.02kW for two hours to bring the bath down.
- 1.02kW x 2 hours = 2.04kWh, about 54p per session.
- Four sessions a week works out at roughly £2.15 a week.
The actual time depends on how much water you use, how cold your tap water is and how cold you want it.
Example 4: heating
Some plunges can also heat the water. Heaters draw a lot of power while they run. A 4kW heater running for one hour uses 4kWh, about £1.05 at the cap rate. If you heat regularly, add that on top of your cooling estimate.
What pushes costs up or down
- Ambient temperature. Warm air and direct sun both add heat to the water and make the chiller less efficient. Expect higher costs in summer and in warm rooms.
- The cover. An insulated cover is one of the simplest ways to cut heat gain. Leaving it off for hours can raise the duty cycle noticeably.
- Insulation. Insulated walls and a raised or insulated base reduce heat flowing in from the air and ground.
- Set temperature. Holding the water colder than you need means more running time. Set it to the temperature you actually use.
- Clean filters and airflow. Restricted water flow or a chiller boxed in without ventilation both reduce efficiency.
- Your tariff. A fixed or time-of-use tariff can be cheaper or more expensive than the cap. If you have cheaper overnight rates, some units let you schedule cooling for those hours.
How to measure your own costs
The most accurate way to know is to measure. A smart meter in-home display will show the change in your usage when the plunge is running. A plug-in energy monitor rated for the appliance's load can track one socket over a week. Multiply the kWh recorded by your unit rate, and repeat in summer and winter for a fair yearly picture.
When you compare models, look at rated power alongside insulation and the cover, not just price. Our guide on how to choose a home cold plunge covers the full checklist, and turning your bath into a cold plunge explains the session-by-session approach.
A quick safety note
The RNLI describes cold water shock, a sudden gasp and rapid breathing that can follow immersion in water below 15°C, and the British Heart Foundation notes that cold immersion can raise heart rate and blood pressure. Speak to your GP first if you have a heart condition, high or low blood pressure, are pregnant or have any other medical condition. Never plunge after drinking alcohol, avoid plunging alone, and start warmer and shorter.
Frequently asked questions
How much does a cold plunge cost to run per month in the UK?
Using the Ofgem cap rate of 26.32p per kWh for October to December 2026, our illustrative examples range from about £23 a month for a 0.4kW chiller running 30% of the day to about £97 a month for a 1.02kW chiller running half the day. Your costs will depend on your unit, the weather, the cover and your tariff.
Does a cold plunge cost more to run in summer?
Usually, yes. Warmer air and sunshine add heat to the water and make the chiller work harder, so it runs for more of the day.
Should I use the cooling capacity or the power rating to estimate costs?
Use the electrical input or power supply rating. Cooling capacity is the heat the chiller removes, which is often several times higher than the electricity it draws.
What is the easiest way to reduce running costs?
Keep the insulated cover on whenever you are not in the water, keep the chiller out of direct sun with good airflow, and set the temperature no colder than you need.