Estimated calculation for an 80 m² dwelling, located within a cold area of the UK, providing 12 hours/day-night heating maintaining the radiators temperature set to 21 ºC.

The water heater would be working 24 hours a day, with a draw-off profile of 120 litres/day and the temperature set to 80ºC. Note that these are approximate figures and should be considered as average depending on the location, orientation and height.