I have used many different brands of heaters in the 50 years I have been keeping fish. In my opinion none of them are very reliable and should ALWAYS be run in a controller of some sort! Most use a set of points like cars did 30+ years ago. There is a reason cars stoped ising them long ago. Every time the heater turns on or off, the points burn a little. As they burn the point they open and close varies.
Even when working properly the built in controllers are very inconsistent due to this. Assuming you have the temp set at 76 in the heater, they typically will turn on and off in a range around that. Ont time it will turn off at 74 and another it might not turn off until 78 or higher. Just puting the on a controller will keep your temperature more consistent and the heater will last longer.
Sadly the electronic heaters I have tried failed early in their life.
Even when working properly the built in controllers are very inconsistent due to this. Assuming you have the temp set at 76 in the heater, they typically will turn on and off in a range around that. Ont time it will turn off at 74 and another it might not turn off until 78 or higher. Just puting the on a controller will keep your temperature more consistent and the heater will last longer.
Sadly the electronic heaters I have tried failed early in their life.