Once you've determined the type of boiler you require, the next consideration is the size.
The size of the boiler (in terms of efficiency) is defined by its heat output. This is expressed in kilowatts (kW).
When a boiler is turned on, the higher its heat output, the more energy it consumes.
Larger homes with more radiators and bathrooms will typically require a higher heat output than smaller homes.
Selecting a boiler that is too large for your home will result in significantly higher heating bills and carbon emissions than necessary.