A microCHP unit including at least one pump (20) and/or fan for circulating a cooling fluid or air through the microCHP unit in normal operation. The microCHP unit comprises an electric power source (32) that is independent from the mains power supply. It also comprises a voltage converter (42) or inverter (44) or both connected between the independent power source (32) and the cooling pump(s) (20) and/or fan(s) (28) of the microCHP unit for converting a supply voltage from the independent electric power source (32) to a different voltage for operating the pump(s) (20) and/or fan(s) (28). A controller (34) is provided to cause the cooling pump(s) 20 and/or fan(s) (28) to operate in the absence of mains power. A charging device (48) is provided to recharge the independent power source (32) when the mains power supply is available.