All Celsia zone controllers achieve a battery life of at least of 2 years with normal AA or AAA alkaline batteries. We have achieved this by designing very efficient electronics and using microprocessors that run highly optimized code.
It is not just low installation cost that makes battery powered wireless thermostats better; they save energy costs and provide better control.
Only an external thermostat, like a Celsia Zone Controller, well away from the heater, can measure and control true room temperature. Our CZCs maintain room temperature within a fraction of a degree ensuring a comfortable temperature with no unnecessary energy consumption.
Being battery powered and wireless makes it easy to locate correctly. For accurate temperature control, a thermostat should be away from direct sunlight, other heat sources, draughts etc. Wiring constraints often lead to compromises.
We have seen non-Celsia heaters with built-in 'room thermostats'. These never work well because the thermostat is so close the heater that it gets heated above room temperature. When this happens it switches heating off while the room is still below set temperature. If you compensate by turning the thermostat up, the heater will come on when the room is already warm enough. This wastes energy and in our tests the room temperature can vary by as much as 8°C.