Which Boiler is Best for You?
Overview of which is the best boiler for you
HOW TO USE THIS GUIDE
Using this Guide: Use this guide to work out which boiler is best for you
What size boiler do I need?
Most boilers are oversized. The average heat requirement for the average UK home is just 6-8kW at peak times yet we commonly find boilers of 15-21kW. The rest of the year your property will require even less. It is important that the boiler is sized correctly otherwise it will rarely operate at 90% efficiency. The tables below provide a rough guide to boiler sizes based on the output of the boiler. For heat only and regular boilers it is straight forward and in fact the smallest boilers on the market will usually be sufficient. For combi boilers it is slightly more complicated because boilers are sized for hot water production and it is common to see outputs of 24kW and upwards.
As an average 3-bed house only needs 8kW of heat, so most combi boilers are oversized for heating in order to get a better hot water performance. It is always worth remembering that 15mm pipework, which is commonly fitted for hot water supplies, can only carry 12.5 litres per minute for hot water. For combi boilers with higher flow rates your installer will need to increase the size of the pipework. If you do not wish to increase pipe sizes then stick with a combi boiler with a flow rate of below 12.5kW. Your installer will also need to adjust the heating output of the boiler down to match the heat requirement of your property, i.e. 6-8kW.
For more help sizing your property try our Guide to boiler sizing and Why oversized boilers are bad for your bank balance and the planet.