What is an EPC? A Guide to Energy Performance Certificates

If you’ve ever bought, sold, or rented a property in the UK, you’ve likely come across the term EPC — but what exactly is it?

An Energy Performance Certificate (EPC) is a document that shows how energy-efficient a building is. It gives the property a rating from A (most efficient) to G (least efficient) and provides suggestions for improving energy use. EPCs are legally required when constructing, selling, or leasing a property, whether it’s a home or a business premise.

In this blog, we’ll break down what an EPC is, why it's important, and how SAP calculations and non domestic EPC assessments fit into the bigger picture.

Understanding the Basics of an EPC

An EPC gives detailed insights into a building's energy use, CO₂ emissions, and potential for savings. It’s a bit like a nutrition label for your property, helping both owners and potential occupants understand energy performance at a glance.

An EPC includes:

The building’s current and potential energy efficiency rating
Estimated energy costs
Recommendations for improving energy performance
Details about insulation, heating systems, and lighting

When Do You Need an EPC?

You’ll need a valid EPC if you:

Are selling or renting out a property
Construct a new building
Own a commercial building being leased or sold

EPCs are valid for 10 years, and you can’t complete a transaction without one. Failing to provide an EPC can result in fines of up to £5,000.

The Role of SAP Calculations in EPCs

For new residential properties, the EPC rating is largely derived from SAP calculations.

SAP (Standard Assessment Procedure) is the government-approved methodology for measuring the energy performance of dwellings. These calculations assess how much energy a property will use and how much CO₂ it will emit, based on factors such as:

Construction materials
Heating and hot water systems
Ventilation
Renewable technologies (like solar panels)

SAP calculations are essential not just for the EPC itself, but also for ensuring that a new building meets Building Regulations Part L in the UK. Developers, architects, and builders rely on SAP assessments to confirm compliance before construction begins.

What is a Non Domestic EPC?

While SAP calculations apply to homes, a non domestic EPC is designed for commercial buildings — such as shops, offices, warehouses, restaurants, and factories.

Unlike residential EPCs, non domestic EPCs are based on SBEM (Simplified Building Energy Model) calculations. These assessments account for the specific use of a commercial property, such as lighting demands in retail stores or HVAC usage in office blocks.

The process involves:

A site visit from an accredited EPC assessor
Collection of building data (floor area, heating systems, occupancy, etc.)
Software modelling to determine energy efficiency
Issuance of the EPC with recommendations for improvements

Non domestic EPCs also use the A–G rating scale but are categorized into different complexity levels (Level 3 to Level 5) based on the size and systems of the building.

Why EPCs Matter

Whether it’s for residential or commercial purposes, EPCs serve several critical roles:

Legal Compliance: You cannot sell, lease, or construct a building without one.
Energy Efficiency: EPCs highlight how to reduce energy use and cut down on utility bills.
Environmental Responsibility: Lower CO₂ emissions contribute to climate change mitigation.
Property Value: Energy-efficient buildings often attract more buyers or tenants and can achieve better resale values.

Conclusion

An Energy Performance Certificate is more than just a piece of paper — it’s a crucial tool for property owners, investors, developers, and tenants. Whether it’s a new home requiring SAP calculations or a commercial space that needs a non domestic EPC, understanding energy performance is vital in today’s property market.

Need help with SAP assessments or EPCs for your business premises? Consult a qualified energy assessor today to ensure compliance and boost your building’s energy profile. https://cpcert.co.uk