An Energy Performance Certificate (EPC) is a document that rates a property’s energy efficiency on a scale from A (most efficient) to G (least efficient). It’s a legal requirement in England and Wales whenever a building is sold or rented out, and it remains valid for 10 years. The certificate shows how much energy a property uses, what it costs to run, and what improvements could bring the rating up.
Why EPCs Exist
EPCs were introduced to make the energy efficiency of buildings transparent for buyers and tenants. Before you commit to a property, the certificate gives you a realistic picture of what your energy bills might look like and where the building falls short. The seller or landlord must commission an EPC before putting a property on the market if no valid one already exists. They’re also required to share it at the earliest opportunity, either when you request information about the property or when you arrange a viewing.
The rating isn’t just informational. It directly affects what landlords can do with their properties. Since April 2020, landlords in the private rented sector cannot let properties with an EPC rating below E unless they hold a valid exemption. The government has signaled a long-term goal of upgrading as many privately rented homes as possible to a C rating by 2030.
What the Assessor Inspects
A qualified energy assessor visits the property and examines the physical features that determine how much energy the building uses. The main areas they look at include:
- Insulation: loft insulation (ideally at least 270mm), cavity wall insulation, and solid wall insulation where applicable
- Windows and doors: whether the property has single, double, or triple glazing, and how well-sealed the openings are against draughts
- Heating system: the type and age of the boiler, the presence of programmable thermostats and thermostatic radiator valves, and whether renewable options like heat pumps are installed
- Lighting: the proportion of energy-efficient bulbs such as LEDs throughout the property
- Hot water: how the system heats and stores water, and whether it’s insulated properly
The assessor doesn’t test how you personally use energy. They’re evaluating the building itself: its construction, its heating infrastructure, and its potential for heat loss. Two identical homes with different occupants would receive the same rating.
How the Rating Is Calculated
The score behind your EPC comes from a government methodology called the Standard Assessment Procedure (SAP), originally developed by the Building Research Establishment. For existing homes, assessors typically use a simplified version called Reduced Data SAP (RdSAP), introduced in 2005 to make assessments faster and less expensive. RdSAP uses a set of standardised assumptions about the dwelling, which reduces the amount of data the assessor needs to collect on site while still producing a reliable estimate.
New-build homes go through a full SAP calculation, which requires more detailed input from architectural plans and specifications. Non-domestic buildings (offices, shops, warehouses) use an entirely separate system called the Simplified Building Energy Model.
The result is a number from 1 to 100, mapped onto the A-to-G letter scale. A score of 92 or above earns an A rating. Most older homes in England fall somewhere in the D or E range.
What the Certificate Actually Shows You
The EPC is a multi-page document, but the front page is the most useful at a glance. It displays the current energy efficiency rating on a colour-coded bar chart (green at the top for A, red at the bottom for G) alongside a potential rating, which shows where the property could land if recommended improvements were made.
Beyond the rating itself, the certificate includes an estimated cost of energy use per year, broken down by heating, hot water, and lighting. It also lists specific recommendations for improvement, each with an estimated cost range and the savings you could expect. These might include upgrading to a condensing boiler, adding loft insulation, installing double glazing, fitting draught-proofing strips, or switching to LED lighting throughout the property. Each recommendation is ranked by how much it would improve the rating and how quickly it would pay for itself.
Properties That Don’t Need an EPC
Not every building requires one. The main exemptions include listed buildings where compliance with energy efficiency requirements would unacceptably alter their character, places of worship, temporary buildings intended to be used for less than two years, standalone buildings with a total useful floor area under 50 square metres, and certain industrial sites and workshops where very little energy is used to condition the indoor climate. Religious buildings across denominations including the Church of England, Roman Catholic Church, Methodist Church, Baptist churches, and the United Reformed Church may retain ecclesiastical exemption from standard building regulations, though this applies specifically to buildings used for worship.
Cost and How to Get One
You can only get an EPC from an accredited domestic energy assessor. Prices typically range from £60 to £120 depending on the size of the property and your location, with London and the southeast generally costing more. The assessment itself takes between 45 minutes and an hour for an average home. Once complete, the certificate is lodged on a central register, and you can retrieve it online using the property’s address or the certificate’s reference number.
Since the certificate lasts 10 years, you don’t need a new one every time you sell or re-let the property, as long as the existing one hasn’t expired. That said, if you’ve made significant energy improvements since the last assessment, commissioning a new EPC could reflect a better rating, which is particularly relevant for landlords who need to meet minimum standards or want to market a property as more efficient.
What a Low Rating Means in Practice
If your property scores an F or G, the practical consequences depend on whether you’re a homeowner or a landlord. Homeowners face no legal penalty for a low rating, though it can affect a buyer’s willingness to pay full asking price, especially as energy costs rise. A low-rated property signals higher running costs and potentially expensive upgrades ahead.
For landlords, the situation is more pressing. A rating below E means you cannot legally let the property unless you’ve registered a valid exemption. Exemptions exist for cases where improvements would cost more than a set spending cap, where required measures would devalue the property, or where a tenant has refused consent for the work. These exemptions are temporary and must be renewed every five years.
Improving a rating from G or F to at least an E is often achievable through relatively affordable measures: topping up loft insulation, draught-proofing doors and windows, upgrading an old boiler, or adding thermostatic radiator valves. The recommendations section of the EPC itself serves as a starting point for planning these upgrades.