The UK running-cost formula
Build the estimate from visible assumptions
Find the unit rate
Use the pence-per-kWh rate on your own electricity tariff, not the standing charge.
Measure daily consumption
A plug-in monitor or suitable energy meter over a representative week gives a more useful figure than a generic claim.
Add ownership items
Budget separately for chemicals, filters, water, routine servicing and eventual cover replacement.
The calculation is: daily kWh × electricity rate ÷ 100. Multiply the daily cost by 365 ÷ 12 for an average month, or by 365 for a year.
Use the UK running-cost calculator to change every assumption and copy the result.
What changes electricity use
Why two similar tubs can cost different amounts
Air and water temperature
Colder weather and a higher set temperature increase the heat that must be replaced.
Insulation and cover fit
Cabinet insulation, plumbing exposure and a dry, well-fitting cover influence heat loss.
Bathing and reheating
Opening the cover, running pumps and adding cooler replacement water all affect consumption.
Filtration settings
Pump schedules, circulation systems and water-care equipment differ between models.
How to compare manufacturer claims
Ask for the test conditions
- Average air temperature during the test.
- Water set temperature and filtration schedule.
- Whether normal bathing and reheating were included.
- The exact cover and insulation specification tested.
- Whether the result is kWh, cost at a named tariff, or a modelled estimate.
Build a complete annual ownership budget
Keep electricity, chemicals, filters, water, servicing, repairs and finance as separate lines. This makes it easier to update one cost without rebuilding the whole comparison.
Electricity-rate source: Ofgem price-cap unit rates. Your supplier tariff and region may differ.