Fully interchangeable with earlier versions using plug-in connectors No need to change the wall mounting box. Compatible with all utility company tariffs. Automatic clock adjusts to accommodate GMT/BST summer/winter time. Accommodates up to three secure off-peak heating periods every 24 hours. Long life battery maintains the clock, display and switch time settings throughout the life of the control. ‘Boost’ button is ideal for short term overriding of the set programme. ‘Boost’ element (in the tank) can be programmed so that it will heat only a small part of your tank at a set time each day. Can be set to accommodate utility tariffs that offer cheaper electricity periods during the day time.