- A boiler that is too big is a common problem, according to Jo Alsop of The Heating Hub, an independent consultancy that focuses on energy efficiency.
- Combi boilers need at least 24kW, but this is for instantaneous hot water, and have heating outputs of about 18kW, still too big for most homes, she says.
- A preheat function in some machines keeps a small amount of hot water ready, which can be sent to the hot tap quickly.
Size matters, and making sure controls...