A Room Thermostat simply switches the heating system on and off as necessary. It works by sensing the air temperature, switching on the heating when the air temperature falls below the thermostat setting and switching it off once this set temperature has been reached. A Programmable Room Thermostat lets you choose the times you want the heating to be on and the temperature it should reach while it is on giving you programmable control. The Programmable Room Thermostat will allow you to select different temperatures in your home at different times of the day and days of the week. This means you can save money and energy by not heating your home unnecessarily. Programmable Room Thermostats are ideal if you have a combination boiler as they do away with the need for a separate heating timer and thermostat.