We all have a relative who is always unplugging appliances and switching off unused plugs to ‘save the planet’. Of course, doing our bit for the environment is a duty we should not shy away from. But perhaps if we really want to make a difference our time is better spent attending clean-up campaigns. Myth #1: Do unused plug sockets use electricity when left on? To draw and use electricity, you need a completed circuit. To complete the circuit you need to plug something in and to switch the plug socket on. If either of these are not done, then the socket will use zero power. If there is something plugged into the socket but the switch is off, then no electricity will be used. Myth #2: Is it better to switch off your water heater after use or keep it on the whole day? Generally, it’s better to switch off the water heater after use. Heating units left on permanently wear out much quicker. Regulating the right temperature from the water heater’s thermostat is clearly more efficient than heating up the water and then mixing it with cold water to get the right temperature. Myth #3: I can save money off the electricity bill by lowering the temperature of the water heater’s thermostat. UK water by-laws recommend that hot water should be stored at not less than 60°C and distributed at not less than 55°C. This is because bacteria thrive at temperatures lower than 55°C. Also, formation of limescale is increased at temperatures higher than 60°C. Myth #4: It is not worth turning things off at the plug. This is possibly true, depending on the appliance. Idle phone chargers and power adapters likely account for less than one per cent of residential energy use. Most modern devices use no more than one watt in standby mode, and many of them use less than 0.5 watts. Modern chargers go down to zero when nothing is plugged into them. Older devices and adapters use significantly more energy when idle.