You are interested in purchasing a new boiler or you want to know whether the one you have is functioning properly. The boiler energy label provides easily understandable facts on which you can compare models and identify their consumption of fuel.
You will find out what each of the symbols and numbers represent, how the number relates to the costs related to running and the environment and what you should notice when searching for a new boiler in the UK. In case you are considering grants, you will also find out why the UK Free Boiler Scheme is important to certain households.
How this Guide will Assist You
- A boiler energy label walk-through of all of its parts.
- Comparison of the performance of boilers in terms of energy consumption.
- Objective positions which influence the number of your labels at home.
- Most useful tips so that you can choose the boiler that meets your requirements and that is economical.
The Importance of the Energy Label to You
The label is an easy method of comparing boilers based on their fuel consumption, hot water efficiency and exhausts. It will assist you in not getting deceived with marketing. An improved boiler would generally consume fewer fuels and be less expensive to operate.
The label will come in handy when purchasing a new boiler or when checking on the replacement options and when you want to know whether you could receive any grant assistance like the ECO4 Scheme.
The Label of Boiler Energy
It will be displayed on new boilers in stores and online. The label is also displayed by installers and websites of manufacturers. The label should exist under regulations (ErP rules) to old models because you would not miss it. In case you are in doubt, request the seller to provide the label or a sheet of specimen.
Just a Glance at One of the Labels
The majority of boiler labels are plain and follow the same design. They show:
- A large bar energy rating of space heating (A to G).
- A percentage number (profitability through the season).
- In case of combi boilers: The performance of hot water or a mark of water delivery.
- Class of NOx emissions and other performance numbers.
- Details of heat output (kW) produced by manufacturer and model.
Here, you will now find out what each part implies one by one.
Simple Grade: The Energy Rating Bar (A to G)
- What it shows
Two bearing a coloured bar will be provided, largest on one end, dark green; on the other, red. The letter provides a cursory evaluation of the seasonal space heating efficiency of the boiler. A = best, G = worst.
- Why it matters
It is with this letter that you will compare models in a short period. A-rated boiler is more effective than C-rated boiler in space heating. However, the letter does not provide all the information about hot-water performance; but you ought to look at the specific efficiency numbers as well.
Percentage of Seasonal Space Heating Efficiency
- What it shows
The label typically provides a percentage of efficiency of seasonal space heating. This figure gives you an idea of the amount of the energy in the fuel which you can convert into useful heat in your rooms during an average heating season.
- How to read it
When there is a boiler demonstrating 92 percent it indicates that you are using 92 percent of the fuel to heat your rooms; 8 percent is wasted. Higher is better. Condensing boilers will tend to have efficiencies of over 90%.
- What it means for bills
The higher the percentage then the cheaper the fuel costs will be. When there is a cost equality of two boilers but one is 5 percent more efficient, you will pay less to warm up your house using the more efficient model.
Heat Output (kW) (This is the Size of the Boiler)
- What it shows
The tags have the useful heat output to be found in kilowatts (kW). This is the rate that the boiler is capable of providing heat.
- How to read it
Compare the kW to your size and heating requirements of your home. A twenty foot flat requires less kW than a 4 bedroom home. Making a poor size selection will cost you. Oversized boilers run on and off and burn more fuel. Undersized boilers will have trouble heating your house.
Tip: You will receive the right kW following a survey of a site. The label merely informs you of what the boiler can do. Contact Home Energy Guide for further information!
Hot Water Performance (Combi and Others)
- What it shows
In the case of combi boilers, the label usually contains a hot water delivery or a figure of the service water efficiency. This demonstrates the efficiency of the boiler to provide hot water in the taps and showers.
- How to read it
A combi with good hot water performance is desired in case you have an on demand hot water (no cylinder). The numbers on the label will assist you in the comparison of speed and hotness of water.
Air Quality (NOx emission)
- What it shows
The label may provide either a NOx (nitrogen oxide) classification or the NOx emittance. One of the air pollutants is NOx.
- Why it matters
The decreased values of NOx improve the quality of the air and can be important in the regions with the pollution thresholds. It might also be desirable that some local planning or installer recommendation be to use a lower NOx rating.
Other Information and Remarks
- Manufacturer and model code
This will help you with precise specifications or to locate the manual to the product.
- Sound level and other icons
Noise levels are indicated on some of the labels (particularly the heat pumps); in the case of boilers the most important numbers are the efficiency and NOx.
Remember: Standard test results at fixed conditions are indicated in the label. Real life may differ.
Instructions on Reading the Label of the Various Types of Boilers
1. Combi boilers
Test the efficiency of space heating as well as the efficiency of hot water. Combi labels usually display the flow of the hot water or a tier of the tap water.
2. System and regular boilers
There is efficiency of the heating system of the space and heat production. Such systems have cylinders, therefore the insulation and cylinder efficiency will influence the real world performance of hot water.
Read more in System vs Regular Boiler: Making the Right Choice.
3. Condensing boilers and labelling
The majority of the new boilers in the UK are condensing. This will be denoted by the label of greater efficiency. When you own an old and non-condensing boiler, it is easy to determine the probable enhancement with the conversion to a modern one, with the label.
Ordinary Labels
- 90%+ efficiency
Very good. You are likely to save a conspicuous amount of bills compared to older boilers.
- 85–90%
Good. Still a solid performer.
- 80–85%
Average. Not the best but much better than very old boilers.
- Less than 80 percent
This is on older models or specialised models; if there is upgrading of your boiler, requires reading.
An Operational Example of the Label
Suppose that you put two boilers of similar size. The seasonal efficiency of Boiler A is 92%; that of Boiler B is 88. Suppose that your heating bill is 1,200 a year, then theoretically you require the same amount of fuel to heat your house, but Boiler A consumes 4% less fuel than Boiler B. That could be an approximate saving of about 48 pounds a year. That accumulates over a few years and more so in case your old boiler is much less efficient.
Real Things that Alter the Figures of the Label
Hopefully you will see that the label provides a standard figure. At home, actual performance is based on:
- Proper installation/sizing.
- Having good controls: Thermostats, timers and TRVs (thermostatic radiator valves).
- Appropriate upkeep and yearly servicing.
- Pipe insulation, cylinder insulation (you have one or not).
- Draughts and house insulation.
- Hot water customs, long baths and taking more than one shower at a time, etc.
Note: An expensive labeled boiler will not be able to perform well when installed incompetently.
Is it Better that You Pick the Boiler with the Best Rating on the Label?
A better rated boiler will normally result in the most advantageous long term value however, you must consider:
- Size and type
A very high-rating boiler may be redundant in large houses where stored water is required.
- Price vs performance
Most efficient models can be expensive in the short run. Balance cost, anticipated savings and duration of stay at the home.
- Install and system match
The correct boiler to your needs and values about plumbing and hot-water is more important than the tiny percentages of various ratings that are such a slight difference.
Real and Label Running Costs
Labels give approximations on running costs but do not provide you with specific numbers regarding your home. The label is not an end, it is just a comparing mechanism. Should include;
- An installer’s survey.
- Your current fuel bills.
- Your hot-water use patterns.
- The impact of maintenance on the energy performance of boilers.
To maintain boiler efficiency at a high rate you will:
- Hiring one engineer to service it once a year.
- In cold weather, the condensate pipe should be checked and cleared.
- Leak radiators/examining system pressure.
- Flushing the system in case of sludge or bad circulatory.
Important: When the boiler is properly maintained, it will be more efficient as indicated on the label.
Labelling, Marketing and the UK Market
You might observe that since ErP regulations in the UK require that boilers sold in the UK should comply with efficiency and labelling requirements. That is to say that most new boilers are condensing boilers and have an energy label. The regulations contribute to the enforcement of uniform information in order to be able to compare.
Combining the Label and Other Purchasing Data
The label is one tool. Also check:
- The time and content of warranty.
- Installer reputation and Gas safe registration.
- Realism reviews and recognized credibility (See our picks in Best Boilers UK 2025).
- Other amenities such as compatibility with smart thermostats.
Government Grants and Schemes
The energy label is used to determine what boilers the scheme will assist in case you are qualified to receive a grant help. The ECO4 is aimed at enhancing energy efficiency and reducing fuel poverty. That is to say that the scheme has a tendency to finance energy-efficient replacements which help save household bills.
How does a good boiler retain the energy performance?
And you are going to have a boiler near to mark performance with due care. Efficiency may decline over 10-15 years when the parts wear off, the controls become obsolete or the system is clogged with sludge. The performance can be maintained with regular maintenance and upgrades of the controls.
A Purchase of Used/Second-hand Boilers (what to check on the label)
In the case of a used boiler, there may be no label, or the label may be out of date. You will check:
- Boiler age and adherence to the present ErP standards.
- History of the service and last repairs.
- Support and availability of spare parts of the model.
Home Energy Guide can Help
Home Energy Guide concentrates on government grants and schemes in order to assist individuals to change to energy efficient heating. In the case you believe a more efficient boiler would help you to reduce your bills but you are concerned about the cost, you will be able to check whether you can receive such assistance. Check your eligibility now!
Home Energy Guide clarifies eligibility provisions and assists you in the manner in which a grant may impact the decision you make in selecting the boiler and the probable costs. What is in the model and which upgrades the scheme can take.
Frequently Asked Questions (FAQs)
The letter (A-G) provides a summary of the seasonal space heating efficiency of the boiler in a flash. A is the best grade. It is a bare-boned comparison but look at the percentage to get the complete picture.
The percentage efficiency is a measure of the amount of fuel that is useful heat. When the percentage is high, the amount of wasted fuel is reduced and the bills are typically low.
Precise saving will be made on the basis of your heating consumption and the efficiency of the old boiler.
Not exactly. Labels use standard tests. Good performance will be based on proper sizing, installation, controls, maintenance, insulation and the use of hot water and heating.
In the case of combi boilers, you should look at the space heating efficiency (percentage/grade) and the figure of the hot-water performance. The latter demonstrates the level of how efficiently the boiler will provide taps and showers on demand.
Yes. The grant schemes usually target efficiency replacements. In case you are eligible for the grant, it may alter the type of the boiler that can be proposed and contribute to the expenses of a model that will make your home perform better in terms of energy efficiency.
