If you’ve recently had a glance at your Energy Performance Certificate (EPC), you might have noticed a colourful graph with loads of letters and numbers. This is the EPC generator graph, and although it may appear somewhat technical initially, it’s a valuable tool to help you determine how energy-efficient your home is.
Whether you’re buying, selling, or renting a property—or just curious about your home’s energy usage—this blog will break it all down in simple terms. We’ll also share how your EPC rating is calculated, what each part of the graph means, and how you can improve it in 2025.
What Is the EPC Generator Graph?
The EPC generator graph is a graphic display of your home’s energy efficiency. It’s included in the Energy Performance Certificate when a property is constructed, sold, or rented.
This chart employs a colour bar chart from A (most efficient) to G (least efficient). Each band indicates the potential cost of energy use and its environmental impact. The better your EPC rating, the less your bills and carbon footprint will be.
How Does the EPC Graph Work?
The graph shows two ratings:
- Current rating – This is your property’s current rating.
- Potential rating – This shows the possible improvement achievable through recommended upgrades.
For instance, a building may currently have a rating of D (55) and a potential rating of B (81) if specific energy improvements are made, such as installing loft insulation or a new boiler.
The ratings are calculated using software that takes into account:
- Wall and roof insulation
- Windows (single or double glazing)
- Heating systems and controls
- Renewable energy sources like solar panels
- Lighting efficiency
- Type of boiler
These elements are assessed to produce a Standard Assessment Procedure (SAP) score, which is then translated into an EPC band.
How Do I Create an EPC Graph?
You cannot create an official EPC generator graph on your own because it must be produced by an accredited Domestic Energy Assessor (DEA) using government-approved software. The assessment is based on factors like:
- Type of heating system (boiler, electric, heat pump)
- Insulation (loft, cavity wall, underfloor)
- Double glazing
- Lighting and appliances
- Energy sources like solar panels
However, you can use a free EPC graph generator tool to estimate your home’s energy performance and visualise what your EPC graph might look like.
What’s a Free EPC Generator?
A free EPC generator is an online calculator that replicates the actual EPC process by requesting you to enter information about your building, including:
- Year built
- Heating type
- Wall and loft insulation
- Number of windows
It then generates an estimated EPC rating and graph, indicating where your home lies on the A–G energy scale.
Advantages of Free EPC Generator Tools:
- Fast and at no charge
- No assessor required
- Useful before selling or renovating your home.
- Appropriate for verifying whether you qualify for energy grants such as ECO4
Tip: Begin by utilising resources such as the EPC Rating Calculator from reputable suppliers.
Who Offers the EPC Graph Service?
Only authorised Domestic Energy Assessors (DEAs) can provide a valid EPC and generate an official EPC graph. These evaluators are registered on schemes endorsed by the UK Government.
You can locate area assessors from:
- The official EPC Register (gov.uk)
- Energy service companies
- Estate agents or letting agencies
The fee will typically range from £60 to £120, depending on the location and size of your property.
What Is the Energy Performance Graph Generator?
The energy performance graph generator is the software that assessors use to work out and generate the EPC graph from details of your home. It’s part of government computer software, such as RdSAP, and requires a training course to operate.
This software analyses your property using the Standard Assessment Procedure (SAP) and outputs:
- A current and potential rating
- Estimated energy costs
- CO₂ emissions
- Recommended improvements
For everyday users, free EPC generator tools simulate this software to help you estimate your Energy Performance Certificate (EPC) rating.
How Do I Create a Free Energy Performance Graph?
While you can’t create an official EPC without an assessor, it is possible to make a free estimate with online software. Here’s how:
- Go to a reliable EPC calculator website
- Input your property type, size, and insulation information.
- Add heating type, windows, and lighting info.
- Submit the form
- Instantly view your estimated EPC graph.
This is great for getting a quick snapshot of your home’s energy efficiency before scheduling an official assessment or planning upgrades.
Why Does Your EPC Generator Graph Matter?
There are three significant reasons why your EPC graph is essential:
- Energy Efficiency: A higher rating indicates that your home requires less energy to heat and power, which helps reduce your utility bills.
- Property Value: Homes with better EPC ratings tend to have higher resale value.
- Legal Requirements: In the UK, landlords must ensure rental properties meet a minimum EPC rating of E. If not, they could face penalties.
Furthermore, as more green mortgage schemes and ECO4 boiler grants become available, a high-quality EPC score can be beneficial in gaining access to government support.
What Affects Your EPC Rating?
Several factors can affect or improve your EPC rating.
| Factor | Impact on Rating |
| Insulation (loft/wall/floor) | Significant improvement opportunity |
| Heating system type | Reducing rating for older systems |
| Double-glazing windows | Adding efficiency |
| Smart thermostats & controls | Small but significant improvement |
| Renewable energy sources | Can significantly improve the rating |
How Can You Improve Your EPC Generator Graph in 2025?
If your EPC rating is currently low, don’t panic. Some steps won’t break the bank to climb the scale.
1. Insulate Your Home
Insulation makes a big difference in keeping your house warm. Loft, cavity wall, or underfloor insulation is usually the simplest and cheapest measure to raise your EPC rating.
2. Get a New Boiler
An inefficient boiler can lower your efficiency rating. Get a new one under the Free Boiler Scheme (a component of ECO4) if you are eligible. Upgrading to a new condensing boiler will make a significant difference to your comfort and EPC rating.
3. Fit Double or Triple Glazing
Not only does this minimise heat loss, but it also minimises noise and condensation.
4. Change to LED Lighting
It’s a minor update, but replacing all the bulbs with energy-efficient LEDs can provide a margin boost to your rating.
5. Add Renewable Technologies
Consider installing solar panels or air source heat pumps. They can significantly lift your EPC potential rating.
EPC Rating Bands & Graph Colours
| Rating Band | Score Range | Colour | Energy Efficiency |
| A | 92-100 | Dark Green | Excellent |
| B | 81-91 | Light Green | Very Good |
| C | 69-80 | Yellow-Green | Good |
| D | 55-68 | Yellow | Average |
| E | 39-54 | Orange | Poor |
| F | 21-38 | Red-Orange | Very Poor |
| G | 1-20 | Red | Extremely Poor |
EPC Generator Graph vs EPC Rating Calculator
You may have come across online tools, such as the EPC Rating Calculator, that enable you to estimate your EPC score.
These calculators take into account the same factors used for an official EPC assessment and provide you with a ballpark figure. As they don’t work as a substitute for a certified EPC, they’re ideal for:
- Planning energy improvements
- Estimating your home’s potential
- Checking if you might be eligible for grants
Using the calculator can help you visualise your current position on the graph and what it would take to reach the next band.
FAQ’S
Yes. The nearer your house is to A (100), the better it is in terms of energy efficiency. Higher ratings typically result in lower energy bills and a higher property value.
The graph provides a visual representation of your home’s energy efficiency rating, making it easy to understand how much energy your house consumes and what areas need improvement.
EPCs remain valid for 10 years from the date of issue.
Yes, certainly! Simple adaptations, such as LED light bulbs, smart thermostats, and draught-proofing, can contribute to a higher rating.
Yes, it’s a legal requirement in the UK when selling or letting out a building.