Consumption control for grid connected micro-generation system

An AC electrical distribution circuit 6 is connected to receive power from a micro-generation system 4, to provide power to a plurality of loads or consumers 8, including a switchable load, and to receive power from or provide power to a grid or public distribution network 2. The switchable load is switched on to receive excess power from the micro-generation system 4, or switched off to avoid drawing power from the grid 2. The direction of flow of power between the distribution circuit 6 and the grid 2 is determined according to the polarity or phase difference between the current and the voltage at the distribution circuit 6. Signals representing the current and voltage are gated together to generate a control signal for the switchable load. The micro-generation system 4 may use a renewable energy source such as solar power. The switchable load may be a boiler or immersion heater. Additional signals may be used in combination with the first, representing the current and voltage, with inverse polarity to the first signals. Switching may be restricted to when the voltage is close to zero.