How EPC Points Are Calculated: The Scoring System Explained
The short answer
- 1 to 100 points, from SAP's modelled energy cost per square metre; the average home in England scores 68, top of band D
- About 7 points for loft insulation to 270mm and about 8 for cavity wall insulation, in our points model
- 4 to 20 points from a heat pump, depending on the heating it replaces
Your EPC score is a number from 1 to 100 based on how much energy your home costs to run per square metre. A score of 100 means almost zero net energy costs. The average home in England scores 68, at the top of band D, and band C is now the most common rating (English Housing Survey 2024). The score is calculated using SAP (Standard Assessment Procedure), a government formula that looks at your insulation, heating, windows, lighting, and any renewable energy. This guide explains exactly how each element affects your score and which upgrades gain the most points.
The EPC bands
Band A is 92 to 100 and G is 1 to 20; the average home in England sits in band D. Band C is the most common, and E is the lowest a home can be let in today.
How ratings change with the age of a home: EPC rating by house age.
| Band | Score | Typical property | Typical metered bill a year |
|---|---|---|---|
| A | 92 to 100 | Rare, and uncommon even among new builds | £1,661 |
| B | 81 to 91 | Typical new build, or a fully retrofitted older home | £1,484 |
| C | 69 to 80 | Most common band in England. Most homes with full insulation and a modern boiler | £1,591 |
| D | 55 to 68 | Where the average home in England sits. Partial insulation, older boiler | £1,834 |
| E | 39 to 54 | Minimal insulation, old heating. The lowest band a home can be let in today | £2,070 |
| F | 21 to 38 | Poor efficiency. Often older homes with no insulation | £2,248 |
| G | 1 to 20 | Very poor. No insulation, often old electric heating | £2,129 |
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The data behind this table
Bills are the median metered gas and electricity use of homes in each band in England and Wales in 2024 (DESNZ NEED 2026, tables 27c and 28c), priced at the Ofgem cap for October to December 2026 including standing charges. Band A costs more than B on the meter: about three in ten band A homes have no gas meter, so more of their heating is on the dearer electricity meter, and band A is a small group. See energy bills by EPC rating for the full breakdown. Actual costs vary by property size and usage.
Use our EPC improvement planner to see your estimated score and which upgrades would move you into a higher band.
How SAP calculates your score
SAP models your home's annual energy cost per square metre from its walls, roof, heating, windows, hot water, lighting and renewables, not your actual bills. The lower the modelled cost, the higher the score.
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SAP (Standard Assessment Procedure) is the government methodology maintained by BRE. It calculates the annual energy cost of heating, hot water, lighting, and ventilation per square metre of floor area. The lower the cost per square metre, the higher your score.
SAP does not measure your actual energy bills. It uses standardised assumptions about occupancy, heating patterns, and internal temperatures so that every home is assessed on a level playing field. Two identical homes with different occupants get the same EPC score, even if one household uses more energy.
The calculation considers the elements below. SAP produces one cost-based score and does not publish a weight for each element: how much each one moves the score depends on the home. The points quoted are what our EPC calculator gives each measure, from a simple points model rather than SAP itself.
1. Walls
Walls are often the largest single heat loss in an uninsulated home. Solid walls (mostly pre-1930 homes) without insulation are the worst performers. Filled cavity walls score well. The assessor records the wall type (solid, cavity, timber frame), insulation status (none, partial, full), and wall thickness.
Solid wall insulation (internal or external) adds about 10 points in our model and cavity wall insulation about 8. Per point, cavity is far cheaper: about £2,200 for a typical home, against about £12,000 for internal solid wall insulation on a typical 3 bed semi (Energy Saving Trust, 2026).
2. Roof and loft
Loft insulation depth is directly measured. No insulation scores very poorly. 100mm scores moderately. The recommended 270mm scores well. The assessor checks the depth at multiple points across the loft.
Loft insulation to 270mm adds about 7 points in our model where there is under 100mm now. It costs about £750 in a bare loft, or about £600 to top up from 120mm (Energy Saving Trust, 2026), which makes it one of the cheapest upgrades per point. Check if you can get free loft insulation through ECO4.
3. Heating system
Your main heating system's efficiency rating feeds directly into the SAP calculation. An old G-rated boiler (under 70% efficient) drags your score down significantly. A modern A-rated condensing boiler (90%+ efficient) scores well. A heat pump makes around 2.5 to 3 units of heat for each unit of electricity in real homes (a median of 2.78 across 428 heat pumps in the government funded Electrification of Heat trial), which offsets the higher price SAP gives electricity. The rating is based on modelled running cost, not on whether the heat is renewable, so the gain depends on what the heat pump replaces: small against a modern gas boiler, large against oil, LPG or direct electric heating.
In our model, replacing a gas boiler over 15 years old with a condensing boiler adds about 8 points. A heat pump adds about 12 against an old gas boiler, 10 against oil, 20 against electric heating and only 4 against a newer gas boiler. Smart heating controls add about 3.
4. Windows
Window glazing type and age affect heat loss calculations. Single glazing scores poorly. Pre-2002 double glazing scores moderately. Post-2002 double glazing or triple glazing scores well. The assessor records the glazing type, frame material, and approximate installation date for each window orientation.
Upgrading from single to double glazing adds about 6 points in our model, and A-rated windows for a semi-detached house cost about £4,800 (Energy Saving Trust, 2026). It is one of the least cost-effective ways to improve your EPC score compared to insulation.
5. Hot water
How you heat your hot water and whether the cylinder is insulated matters. An uninsulated hot water cylinder loses significant energy. A well-insulated cylinder (factory-fitted foam jacket) scores well. Combi boilers avoid cylinder losses entirely. Solar thermal panels for hot water boost this element significantly.
6. Lighting
The proportion of low-energy lighting (LED or CFL) in your home affects the score. SAP counts the total number of light fittings and the percentage that are low-energy. A home with 100% LED lighting scores a few points higher than one with mostly halogen or incandescent bulbs.
Switching to LED throughout adds 2 or 3 points in our model. Bulbs you fit yourself cost little, and our calculator allows £100 to £300 for a whole house, so per point it is one of the cheapest improvements.
7. Renewable energy (bonus points)
Solar PV panels, solar thermal, and wind turbines generate energy that offsets the home's consumption in the SAP calculation. In our model a typical 4 kW solar PV system adds about 8 points, for £5,000 to £7,000. Read Are Solar Panels Worth It? for the full financial analysis.
8. Air tightness and thermal bridging
SAP includes default assumptions for air leakage and thermal bridging (heat loss at junctions between building elements). If a home has been air-tested, the actual result can be used, which often improves the score. Draught-proofing does count. The assessor records the share of windows and doors that are draught-proofed, and SAP lowers the modelled air leakage to match. The effect on the score is usually small, and an air test can improve it further.
Which upgrades gain the most EPC points
Per pound, LED lighting and heating controls come first, then loft insulation, then cavity wall insulation at about £275 a point. A heat pump adds 4 to 20 points, depending on the heating it replaces.
| Upgrade | Points in our model | Cost | Points per pound |
|---|---|---|---|
| LED lighting (full house) | 2 or 3 | £100 to £300 | Very high |
| Heating controls upgrade | About 3 | £150 to £400 | Very high |
| Hot water cylinder insulation | Small, on homes with a cylinder | About £18 for a jacket | Very high |
| Loft insulation (under 100mm to 270mm) | About 7 | About £750 bare, £600 top-up | High |
| Cavity wall insulation | About 8 | About £2,200 | Moderate |
| New condensing boiler (replacing one over 15 years old) | About 8 | About £3,500 for a 3 bed home | Moderate |
| Heat pump | 4 to 20, by the heating it replaces | Median £12,700 for a 3 bed semi, less a £7,500 grant | Moderate |
| Solar PV (4 kW) | About 8 | £5,000 to £7,000 | Low |
| Double glazing (full house) | About 6 | About £4,800 for a semi | Low |
| Solid wall insulation | About 10 | About £12,000 internal, £15,000 external | Low |
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The data behind this table
Points are what our EPC calculator's simple points model gives each measure, not SAP output, and the real gain depends on the home. Insulation, window and cylinder jacket costs from the Energy Saving Trust. The heat pump cost is the median reported under the Boiler Upgrade Scheme in 2025/26, before the £7,500 grant (£9,000 when it replaces oil or LPG). The boiler cost is the DESNZ average of about £3,500 including VAT for a new gas boiler. "Points per pound" is a relative measure of cost-effectiveness.
On points per pound the usual order is LED lighting and heating controls, then loft insulation, then cavity wall insulation at about £275 a point. A new gas boiler and a heat pump replacing an old gas boiler come next and cost about the same per point, about £440 for the boiler and £430 for the heat pump after the £7,500 grant. Grants can make insulation free, which moves it to the front. Use our EPC improvement planner to model the exact impact for your property.
Free upgrades first
If you qualify for ECO4, you can get loft insulation, cavity wall insulation, and even solid wall insulation at no cost, but the scheme ends on 31 December 2026. Use our grant eligibility checker before spending anything.
How an EPC assessment works
An assessor visits for under an hour and enters the details into SAP software. An EPC costs £55 to £150, or £65 to £95 for a typical two or three bedroom house, and is valid for 10 years.
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Book an EPC online with Energy Performance Certificates, a national provider, from £65 in some areas when we checked on 26 September 2026. A local assessor on the government register of assessors can be cheaper, so compare.
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A qualified Domestic Energy Assessor (DEA) visits your property and records every element that feeds into the SAP calculation. The visit takes under an hour for most homes. They will check loft insulation depth, wall construction type and insulation, window glazing type and age, boiler make, model, and installation date, heating controls, hot water system, number and type of light fittings, and any renewable energy systems.
The assessor enters all this data into SAP software, which produces the EPC score, band, and a list of recommended improvements with estimated cost and savings. The certificate is then lodged on the national EPC register and is valid for 10 years.
An EPC costs £55 to £150, and £65 to £95 for a typical two or three bedroom house (see how much an EPC costs). Find accredited assessors with the GOV.UK assessor finder.
Common scoring mistakes
Missed cavity insulation, patchy loft checks, uninsulated extensions and wrongly assumed boiler age can all lower your score. A missed cavity fill costs about 8 points in our model, so show the guarantee certificate.
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The assessor missed your insulation. If cavity wall insulation was installed but the assessor cannot see evidence of drill holes or a guarantee certificate, they may record it as uninsulated. In our points model that costs about 8 points. Always provide the insulation guarantee certificate during the assessment.
Loft insulation was patchy. If the assessor can only access one part of the loft and insulation is thin or missing there, they record the lowest depth. Ensure the loft hatch area is representative, or show them multiple access points.
Old extension dragging the score down. If your home has an uninsulated extension, it brings down the whole property's score. Insulating the extension is often a quick win.
Boiler age assumed wrong. If the assessor cannot read the boiler's data plate, they may assume a default (lower) efficiency. Point out the boiler model and installation date. Read our heat pump vs boiler guide if you are considering replacing it.
Frequently asked questions
How is an EPC score calculated?
Using SAP, which estimates annual energy cost per square metre. It looks at insulation, heating, windows, lighting, and renewables. Use our EPC calculator for an estimate.
What does each EPC band mean?
A (92 to 100) is the most efficient and uncommon even among new builds, while B (81 to 91) is typical of new builds. C (69 to 80) is the most common band in England, and D (55 to 68) is where the average home sits, at 68 points. G (1 to 20) is the least efficient. Privately rented homes must meet a band C equivalent standard from 1 October 2030. See our improvement guide for how to reach C.
Which improvements gain the most EPC points?
In our points model, a heat pump gains the most when it replaces electric heating (about 20 points) or a gas boiler over 15 years old (about 12). Solid wall insulation adds about 10, and cavity wall insulation, solar panels and a new condensing boiler about 8 each. Loft insulation adds about 7. LED lighting and heating controls are the cheapest per point.
Can I calculate my own EPC score?
You can estimate it with our EPC calculator, which is a rough points model rather than an assessment. An official EPC needs a visit from an accredited domestic energy assessor, costs £55 to £150 and is valid for 10 years.
How much does an EPC cost?
£55 to £150, and £65 to £95 for a typical two or three bedroom house. The visit takes under an hour for most homes. Find assessors with the GOV.UK assessor finder.
Data sources
The method comes from BRE's SAP and the GOV.UK EPC register. Costs come from the Energy Saving Trust and DESNZ, bills by band from DESNZ NEED at the Ofgem price cap, and average ratings from the English Housing Survey.
Show every source
SAP methodology from BRE. EPC register from GOV.UK. Upgrade costs from Energy Saving Trust. New gas boiler cost from the DESNZ Boiler Upgrade Scheme 2026 to 2030 summary business case, footnote 8. Bills by band from the DESNZ NEED consumption tables 2026, priced at the Ofgem price cap, October to December 2026. Average rating from the English Housing Survey 2024 to 2025. Heat pump efficiency from the Electrification of Heat trial.