A fuel-fired appliance with thermoelectric-powered secondary electric heating has a burner providing hot combustion gasses into a first housing. A second housing containing a fluid receives heat from the combustion gasses in the first housing. A thermoelectric device attaches to a surface of the appliance heated by the combustion gasses and generates a voltage. An electric heating element is in thermal communication with the second housing, and the electric heating element is electrically connected to the thermoelectric device.