You will want to be sure that you understand how to work this instrument. Temperature controlled Hot Tub Heater One type of hot tub heater that you can purchase is a temperature controlled hot tub heater. This is one that will rise to a certain temperature and then cut off. If you get a temperature controlled hot tub heater, you do not have to worry about the water getting too hot in the tub. The unit should shut off automatically once the water has heated to a sufficient temperature. Some temperature controlled models allow you to choose from several different preset temperature choices. With others you can manually enter the temperature of your choosing and still others may only have one hotness setting.