Every time you turn on a hot water tap or shower when the combi boiler is cold, CombiSmart will save both water and gas.
Exactly how much you will save will depend on various factors, including number of people in your household, your attitude to water in general and in which part of the country you live. You'll save more if you are on a water meter because you'll be using less water and therefore gas while the boiler heats to the right temperature. Even if you're not on a water meter, you'll still save around £35 every year, year on year.
Figures based on turning on a hot water appliance 24 times within a 24 hour period with the boiler at cold, 6 months (180 days) during a year. Test results as per a 30 cdi – Worcester Bosch boiler. Gas prices based on £0.0449 per kWh (Energy Saving Trust 2012) and an average £0.0025 per litre supplied and taken away (OFWAT February 2011/12). Please note water prices will vary by Water Company. KgCO2 figures from EST 0.183KgCO2/kWh and Water UK 0.79gCO2/litre. Tests conducted by independent consultancy Enertek International.