A spa has an insulated cabinet with an uninsulated shell disposed therein. A filter assembly is downstream of a water intake. A heater is downstream of the filter assembly and a pump is downstream of the heater. A diversion line is in fluid line connection with an outlet of the pump. An ozonizor is in fluid communication with the diversion line. The filter assembly is coupled to the diversion line. A data processing system is coupled to the heater, pump, a control panel and a temperature sensor, wherein the data processing system responsive to when the actual temperature of an amount of water in the shell is a magnitude in degrees below a set temperature 1) turns the heater off if it is on or does not turn the heater on if it is already off and 2) turns the pump on if it is off or if it is already running does not turn the pump off.
