Is a 30KW boiler a good output?

For combi boilers, the kW rating equates primarily to more hot water so, the bigger the number, the more hot water the boiler is able to deliver. A 30kW combi boiler output is considered ‘middle of the range’ and is very popular with many homeowners. However, do remember that the kW number alone for a combi boiler doesn’t necessarily guarantee ‘better’. To make true comparisons between gas boiler makes you will need to look at the industry standard of DHW (Domestic Hot Water) output with a 35 degrees C temperature rise. For example, some boiler makes may offer a 30kW combi boiler delivering 12 litres a minute DHW at a 35 degree rise, whereas the Alpha E-Tec 28kW delivers the same output. In such cases 30kW will appears better at first glance, but in reality, it is not.

There is also a misconception that that “bigger is better” when it comes to gas system boilers as well. However, this is not really the case for the vast majority. Something like 80% of houses in the UK actually only need 8kW of input to heat the home, and perhaps twice that to re-heat their hot water cylinders. Granted, boilers will modulate down (i.e. reduce heat input) according to actual heat load in the house, but it is still beneficial for installers and homeowners alike to properly discuss the subject of sizing the heat source correctly, and not over-sizing; as has been the case for decades.