BUT if you use a lot of hot water, and you need to reheat the store quicly, and it's a modern cylinder with a coil capable of transferring 25kW into the water, a (say) 12kW boiler wouldn't be ideal! If the weather were freezing and you had 4 high flow long showers on the trot, you'd be cold and run out of HW.
I know some of the official calculators say to allow 2kW for the HW. Moi thinks they are silly, so there.
I know some of the official calculators say to allow 2kW for the HW. Moi thinks they are silly, so there.