There are so many factors that influence running costs, that it would be irresponsible for any spa company to quote exact costs. These factors include the ambient air temperature, quality of the spa cover etc.
A typical 1500 litre spa filtration cycle runs for 8 hours without heating, to keep the water clean. The circulation pump draws 0.35 kW.
If you are paying $0.25 per kW then 0.35 x 8 hrs = 2.8 kW/h x $0.25 is $0.70 per day to filter and clean.
The typical heater is 3 kW and on average will turn on 10 minutes an hour to maintain heat. 5 min x 24 hrs = 1.2 hours x 3 kW = 7.2 kW/h x $0.25 = $0.90
So adding the $0.90 + $0.70 = $1.50 per day. Times this by 365 days and it comes to approximately $550 per year. This is a very rough estimate as there are so many variables such as the spas position, how much it is being used, for how long is it being used, what is the set temperature, etc all play a part with running costs.