An electronic programmer allows you to set ‘on’ and ‘off’ time periods. Some models switch the central heating and domestic hot water on and off at the same time; while others allow the domestic hot water and heating to come on and go off at different times. Electronic programmers offer a range of advanced features coupled with simplified ‘menu driven’ programming to help save energy. They come with automatic/manual clock and provide up to three ON/OFF settings for each day of the week. They support adjusting heating programs temporarily using, ‘override’, ‘advance’ or ‘boost’.