Are New Boilers More Efficient?

Are new boilers more efficient than my current boiler?

Chances are yes. But that depends on a few things. If your boiler is an old-style heavyweight boiler. And you are replacing it with a modern condensing boiler. Your annual saving will be on average £652 a year (source: Sedbuk). Heating and hot water can account for over half of what you spend on energy bills in a year, so having an efficient boiler can make a big difference.

All modern, well-maintained boilers burn their fuel efficiently. However, they do  inevitably lose some heat in the hot gases that escape up the flue (a pipe used to extract fumes and supply fresh air to the boiler).

Modern boilers are more efficient than older boilers for several reasons, but their main advantage is that they are ‘condensing’. A condensing boiler recovers more heat from the exhaust flue gas and uses it to heat the central heating water, making it more efficient than older boilers.

Modern condensing boilers are labelled between 92-94% efficient ErP, or more commonly labelled ,A-rated. Boilers over 25 years old can be as little as 60% efficient, or G-rated. However,  it isn’t as simple as swapping out an old boiler for a new boiler to reduce your fuel bills. Condensing boilers are not A-rated out of the box. Most newly installed boilers run 10-25% under their A-label efficiencies because  installers have not been trained to set condensing boilers up correctly. We always recommend you ensure your boiler installation company is Gas Safe registered, experienced and works closely with manufacturers to stay up to date with their training.


Which are the most efficient boilers?

The Viessmann 200 Combi boilers are up to 98% efficient


Worcester Bosch combi boilers are up to 94% efficient


Vaillant Boilers up to 94% efficient


Ideal and Baxi are between 91-94% efficient


All boilers must have an ‘A’ rating with factory tested efficiencies of 91% or higher. Unfortunately,  these levels are rarely achieved. The boiler is just one component in the overall heating system. The whole system must work effectively for the boiler to achieve 90% or more. However, there are some ways you can maximise the efficiency of your new boiler to help it achieve that A-Rating.


Ensuring maximum efficiency is achieved

  • Have a low minimum output.

All modern boilers have modulating burners. A modulating burner is one that can reduce its output to suit the demand placed on it. The lower the minimum output of a boiler the more efficient it can be.

Imagine you are driving a car down the motorway at 70mph. Older boilers can only put their foot flat to the floor, or off the pedal completely. A modulating burner can see that that the speed is approaching 70mph. And ease off the gas and allow the engine to work at a lesser rate to maintain the speed.


  • Be sized correctly

Most UK homes, need on average 6-8kW on a very cold day and even less the rest of the year. Yet most boilers far exceed this on their heating capabilities. This is why it’s important that the maximum output of the boiler is rated down to suit the property it will be heating.

You may be asking yourself why do you need a 30kw combi boiler if you only need 6-8kW to heat your home? Combi boilers are designed to supply instant hot water to your taps at different flow rates. This is where the full output of the boiler is used.

  • Be paired with compensation controls


Modern boilers can modulate their outputs to suit the demand as we have already discussed. But to get the most out of your boiler you need to pair it with compensated controls. This can be Load or weather compensation. Older technology when it comes to boiler controls simply have two commands to tell the boiler; heating on/ heating off.

A modulating boiler control is the most efficient way to control your boiler. Modulating controls have the ability to talk to your boiler other than the basic on or off command.  When a modulating control recognises that your room is near the desired temperature. It will modulate the boiler down to a lesser work rate. Saving you money and keeping higher levels of comfort in your home. Reducing the radical temperature swings

If you’d like to find out more about efficient boiler installations, why not get in touch with our team of experts here.