A system for reducing the voltage of an AC electrical supply to a load for the purpose of energy efficiency, the system comprising: a) a transformer having primary and secondary windings in circuit between an AC electrical supply and the load, and b) bypass means to cause the transformer to be taken out of circuit and to cause the electrical supply to be connected directly to the load in the event of a predetermined overload of the transformer; characterised in that c) the bypass means comprises: i) a bypass switch to divert the supply directly to the load, ii) means to determine the temperature of the transformer, iii) means to measure the electrical current through the load, iv) control means to receive signals from the temperature determining means and from the current measuring means, and to operate the bypass switch at a maximum predetermined level of either one of both said temperature and current; and in that the system further comprises: d) failsafe means to interrupt current through the secondary winding of the transformer in the event that the bypass switch fails to operate at either one of said predetermined maximum levels, wherein the failsafe means includes i) a thermal trip device connected to the secondary winding of the transformer and adapted to interrupt the connection of the secondary winding of the transformer to the supply at a predetermined elevated temperature of the transformer after a predetermined period; and ii) a fuse connected in series with the supply and the thermal trip device and adapted to interrupt the connection of the secondary winding of the transformer to the supply at a predetermined elevated current level below a maximum current rating of the thermal trip device. a) a transformer having primary and secondary windings in circuit between an AC electrical supply and the load, and b) bypass means to cause the transformer to be taken out of circuit and to cause the electrical supply to be connected directly to the load in the event of a predetermined overload of the transformer; characterised in that c) the bypass means comprises: i) a bypass switch to divert the supply directly to the load, ii) means to determine the temperature of the transformer, iii) means to measure the electrical current through the load, iv) control means to receive signals from the temperature determining means and from the current measuring means, and to operate the bypass switch at a maximum predetermined level of either one of both said temperature and current; and in that the system further comprises: i) a bypass switch to divert the supply directly to the load, ii) means to determine the temperature of the transformer, iii) means to measure the electrical current through the load, iv) control means to receive signals from the temperature determining means and from the current measuring means, and to operate the bypass switch at a maximum predetermined level of either one of both said temperature and current; and in that the system further comprises: d) failsafe means to interrupt current through the secondary winding of the transformer in the event that the bypass switch fails to operate at either one of said predetermined maximum levels, wherein the failsafe means includes i) a thermal trip device connected to the secondary winding of the transformer and adapted to interrupt the connection of the secondary winding of the transformer to the supply at a predetermined elevated temperature of the transformer after a predetermined period; and ii) a fuse connected in series with the supply and the thermal trip device and adapted to interrupt the connection of the secondary winding of the transformer to the supply at a predetermined elevated current level below a maximum current rating of the thermal trip device. i) a thermal trip device connected to the secondary winding of the transformer and adapted to interrupt the connection of the secondary winding of the transformer to the supply at a predetermined elevated temperature of the transformer after a predetermined period; and ii) a fuse connected in series with the supply and the thermal trip device and adapted to interrupt the connection of the secondary winding of the transformer to the supply at a predetermined elevated current level below a maximum current rating of the thermal trip device.