Once heated up. I am about £1 a day keeping it set to 38 and the circulation on. Scotland - Hawaii Lazy Spa - Sitting on decking, on astro, then on lazy spa foam mats & a layer of bubble thermal stuff. Initial fill up as well - used hot water from houses internal water tank.
Initial heat up time and cost can be reduced massively by filling from kitchen mixer tap attached to hose set to about 40. Time taken. 2 hours 30 minutes which also includes filling it. That means after cleaning it out I can be in the tub in under 3 hours. When it's about half full I'll activate the pump but not the heat to mix the water. Cost £4.20. What a saving! Almost half. The tap to hose adaptor cost £10 which will pay for itself in 3 fill ups.