The word self-sufficient means “to be dependent on no support”. So energy self-sufficient means that an object (e.g. a house or a device) does not require any energy from outside. It supplies itself with energy.

The essentials radiator thermostat energy self-sufficient BT is an example of an energy self-sufficient device. Normal smart home radiator thermostats need batteries (i.e. extra energy that has to be supplied) to work. The essentials radiator thermostat works without batteries. It obtains its energy supply from the available heating heat with the help of an integrated thermoelectric nanogenerator. This principle of energy generation is called energy harvesting .