A mechanical thermostat consumes more electricity than a digital one because it's inherently inaccurate. It maintains a higher temperature than its setting and it allows the temperature to fall below its setting before re-energizing the heater, which uses up more power.
In contrast to this, a digital thermostat provides better accuracy and control, resulting in a savings in electricity consumption [source: DIY Doctor].
Here's what you'll need to replace a wall-mounted thermostat with a programmable digital one:
Here's how to replace that thermostat:
- Turn off the thermostat's circuit breaker.
- Remove the thermostat cover by either pulling it off or removing the screws, depending on the model.
- Remove the mounting screws and gently pull the thermostat away from the mounting plate.
- Label each wire with the symbol or letter of its thermostat terminal.
- Disconnect the wires from the thermostat and wrap them around the pencil or dowel so they don't slip back into the wall. Important: If the thermostat contains a mercury tube, don't toss it in the trash. Ask your local waste management authority how to dispose of it safely.
- Remove the mounting plate from the wall.
- Align the new mounting plate over the hole. If the screw holes don't match up with the existing anchors, hold the plate level and mark new holes with the pencil. Drill the holes and insert new anchors.
- Pull the wires through the mounting plate and then screw the plate firmly to the wall.
- Check the thermostat's terminals for symbols or letters. If the markings match the wire labels, connect the wires to the corresponding terminals. If the terminal markings are different, check the installation or user's guide for wiring instructions.
- Snap the thermostat onto the mounting plate, and then insert the batteries. Note: Some models require you to reverse this procedure.
- Turn the circuit breaker on.
- Switch the thermostat to Auto and set the thermostat higher than the temperature reading. The heater should switch on within a few seconds.
- Program the thermostat according to the user's manual [source: Donovan].