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How to improve my boiler efficiency

Discover how to keep your boiler running efficiently, so you can stay warm – and even save money on your energy bills.

What is boiler efficiency?

An efficient boiler is one that uses the least amount of energy and money to keep your home warm and cosy.

An inefficient boiler does the opposite. It uses more energy to run, costing more – and it can leave you with lukewarm radiators and no hot water.

How efficient is my boiler?

Age can be a rough indicator of your boiler’s efficiency. While modern condensing boilers have to be A-rated with an efficiency of 90% or more, older non-condensing boilers can be a lot lower. A boiler over 15 years old could be 85% efficient and one over 20 years old could be only 70% – definitely room for improvement. 

Another sign of efficiency are ratings, so we’ll get on to those next.

Boiler efficiency ratings explained

In the UK we use a few types of rating systems. Luckily, they’re not as complicated as they sound.

What is ErP?

ErP (Energy related Products Directive) is used for modern boilers. It’s shown as a certified letter rating where A+++ is top of the class and G is the lowest. 

What is SEDBUK?

SEDBUK stands for the rather catchy Seasonal Efficiency of Domestic Boilers UK – the rating system used before ErP was introduced in 2015. SEDBUK ratings are displayed as a percentage, to avoid confusion with ErP’s letter rating system. SEDBUK 2009 is the rating used since the system was adjusted in 2009, and SEDBUK 2005 is the older system used before this.  

Effects of an efficient boiler - How much could I save?

Upgrading your standard older boiler to a new high-efficiency model is an investment. You’ll enjoy the peace of mind that comes with knowing you’ll have hot water and a warm house. And, over time, it should save you money. With heating accounting for around 55% of energy bills per year, this upgrade could have a big effect – check out what else affects your gas and electricity bills

The Energy Saving Trust is a leading and trusted organisation that helps people save energy and money, offering lots of information on boiler and home efficiency. It can even calculate how much money you could save, depending on your boiler’s age and efficiency rating. Believe it or not, you could save up to £3151 each year!

6 quick ways to make my boiler more efficient

Here are the top tips to keep your boiler and central heating system ticking along nicely.

1. Get a routine service

Just like a car, your boiler needs regular servicing to keep it running smoothly and safely. It can help make it more efficient, detect whether something is wrong - and prevent small issues turning into big problems.

So always book a boiler service with a Gas Safe registered engineer – every year. If you're an OVO member, you can benefit from a free annual service (in your first year) when you take out cover with OVO HomePlan2. 

2. Bleed your radiators 

Along with the perk of improving your radiators’ heat efficiency, this minor maintenance task should lead to cheaper bills. To work out if your radiators need bleeding, fire up the heating – if they take a while to warm up or have cold spots at the top it could be worth bleeding your radiators.

Read our guide on how to bleed your radiator in 7 easy and quick steps

3. Top up the pressure

Low pressure is bad news for a boiler’s efficiency and energy bills. Equally, high pressure can prevent it from working properly. So make sure it’s in the sweet spot – between 1 and 2 bars of atmospheric pressure. 

Read our guide on how to repressurise your boiler to make sure it's always up and running 

4. Insulate your pipes

Lag your central heating pipes with foam tubes from a DIY store – they’re easy to fit and you can do it yourself. It’ll reduce heat loss through the pipes, meaning your boiler doesn’t have to work quite so hard.

5. Run your heating every month – even in summer

Pop your heating on for 15 minutes every month right through the year – even when it’s hot outside. Doing this might feel a bit odd, but it’ll keep things active and avoid any problems during winter.

6.  If all else fails, consider upgrading to a high-efficiency boiler

While regular servicing and maintenance will keep your boiler working efficiently for longer and avoid the undesired boiler breakdown, the time will always come when you need to replace it. Sometimes it’s sensible to do that sooner rather than later, as old boilers can be expensive to run.

Find out about the prices and potential savings of combi boilers here so you can make an informed choice, if this is your next step. Think it’s time for a new boiler? See our boiler replacement options.

Which are the most efficient boilers?

Condensing boilers

Currently the most efficient out there, condensing boilers can recover more energy from condensing vapour – that’s where they get their name.

Combination boiler 

Known as a combi boiler, this type provides hot water on demand. Most components are contained within the boiler so it’s a compact option.

Your choice of boiler and how efficiently it runs is also affected by the size of your home, how much hot water you use and the type of fuel you have access to. Find out more about the different types and how to be more efficient with heating and hot water. 

Ready to know more? Find out everything to do with combination boiler prices and savings here

Where should I get a new boiler?

You can get an A-rated, award-winning boiler from CORGI HomeHeat (part of the OVO family). Here you’ll also find out how to tell if it could be time for a replacement. OVO members can visit MyOVO for all the latest offers from CORGI HomeHeat. 

If you are considering to buy a new boiler, read our practical guide on types of boilers and how to choose the right for your home.

Boiler efficiency and the environment

Heating is one of the highest uses of energy out there. So boiler efficiency has a big part to play in reducing our impact on the environment. Modern green boilers are more efficient, but they do still have some impact on the environment. There are two main types:

Biomass boilers burn renewable organic materials, like wood, to produce heat. They produce carbon emissions but the amount is low – about the same levels as the plant or tree used to create the fuel would have absorbed in its lifetime. 

Condensing boilers are fuelled by gas or oil. As mentioned earlier, this type recovers more heat from the combustion process in the form of condensed water vapour: making them more efficient. But the use of gas and oil means they still contribute to environmental pollution. 

Green boilers are engineered using newer technology that’s changing the heating industry for the better. Here are 3 important ways: 

  • Emissions

These newer boilers are engineered to abide by strict emission guidelines and energy-efficiency measures. Standards are high.  

  • Efficiency 

Green boilers are manufactured to reduce heat loss and maximise heat transfer. An efficient system is better for business and the climate. Win win.

  • Cost

Green boilers use less fuel to run than older, traditional boilers.

Ready to cut your carbon emissions even further? Check out OVO Beyond: it’s the personalised programme to help you fight the climate crisis, by fighting energy waste.

Get a quote


Terms & Conditions

1These are estimated figures based on installing a new A-rated condensing boiler with a programmer, room thermostat and thermostatic radiator controls (TRVs) in a gas-heated home from an older boiler with a programmer and room thermostat. Savings will vary depending on the size and thermal performance of your home. Figures are based on fuel prices as of March 2019. Source; Energy saving trust.

2Terms, conditions, exclusions and cancellation charges apply. 

OVO Energy Ltd is registered in England and Wales company number 06890795. Registered office at 1 Rivergate, Temple Quay, Bristol, BS1 6ED.

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