This is probably the most difficult question we are asked – because there are so many variables.
Size of tub
System specification
Position of tub
Geographical location
Season
Usage
Water costs
Electricity costs
Experience of ownership will improve efficiency of course and we can give you plenty of tips in that respect. We feel safe in saying though, that even in the harshest of conditions (mid winter in an open, exposed position) £3 a day should be the maximum. Generally, an average of £1 – £2 a day would be the norm, and even less in some circumstances.

Even though a hot tub holds more water than a similar spa, running costs should be roughly the same because they have less surface area for heat loss.