Here at K&M Maintenance we know that purchasing a new boiler is difficult enough without wondering what all the different terms mean, so here is a guide to all of these confusing technical terms to help make your search easier.

Condensing Technology

This simply refers to the boilers ability to condense the gas or oil into heat for your home, to ensure that at least 90p of every £1 you spend on fuel will be converted and less fuel will be wasted.


When the boiler produces heat, some condensation will also be produced and can be seen leaving the boiler, especially on cold days. Some of this condensation will also be collected inside the boiler and will drain away. This is all perfectly safe and a simple part of the way that boilers operate.

ErP Rating

This is the A++ to G rating that you will see on all boilers when out shopping or browsing for your new boiler. This rating refers to the energy efficiency of the boiler as well as the heating and hot water performance. A++ refers to the most efficient with the highest performance, with G being the least efficient with the poorest performance.

Flow Rate

Referring to the amount of hot water that will come out of your tap in a minute, flow rate is relevant to combi boilers. The higher the flow rate the larger the volume of hot water that will be produced from the hot water tap per minute, which means the boiler has to work for less time, using less gas to fill a bath or sink, and ultimately costing you less money. Having said that, it is important to note that flow rate is determined by the amount of water and the pressure of the water entering your property from the water main, so homes with poor water pressure from the mains, may still have poor water pressure even with a boiler with a great flow rate.


This stands for Seasonal Efficiency of Domestic Boilers in the UK and provides a percentage rating for the efficiency of the boiler. This has been incorporated as part of the ErP rating to give a good overall understanding about the boiler you are purchasing.

We hope this glossary helps make choosing a new boiler a little easier.