How do I calculate the fuel cost of operation of a spa or pool propane heater? Last Saturday I routed my spa heater to the pool and raised the temperature of the pool 14 degrees in 6 hours to make it tolerable to swim. The heater never reached setpoint so it was on the entire 6 hours.
My spa propane heater is rated 400,000 btu.
Assume $2.35 per gallon of propane
How do you calculate the gallons of Propane used per hour?