Not sure what separates a commercial EPC from a DEC? The two certificates are often confused, but they measure very different things.
In short, an Energy Performance Certificate (EPC) shows how efficient a building is designed to be, while a Display Energy Certificate (DEC) demonstrates how efficiently it is actually being used.
In this guide, we’ll explore the key differences between EPCs and DECs, so you know which applies to your building and why it matters.
Note: While EPCs also apply to domestic properties, DECs only apply to non-domestic properties. This article covers the differences between non-domestic EPCs and DECs.
Understanding the Energy Performance Certificate (EPC)
Non-domestic Energy Performance Certificates (EPCs) rate the energy efficiency of a commercial building on a scale from A+ (net zero carbon) to G (least efficient). The score is calculated using details of the building’s fabric and services – such as insulation, glazing, heating, ventilation, and lighting – combined with standardised assumptions about occupancy and usage. Importantly, it does not reflect how the building is operated in practice.
Only a suitably qualified and accredited energy assessor can carry out an EPC survey and issue the report and certificate.
Which buildings need a commercial EPC survey?
In England, Wales, and Northern Ireland, a non-domestic EPC is required to build, sell, or let a commercial property. There are three levels of non-domestic EPCs, based on the building’s complexity:
- Level 3: Simple commercial buildings with standard features and basic air-conditioning (e.g., small shops, cafes, and restaurants).
- Level 4: Larger or more complex buildings with advanced HVAC systems, as well as all new build commercial properties (e.g., large offices, supermarkets).
- Level 5: Highly complex buildings with specialist features and requiring detailed modelling software (e.g., shopping centres, airports, skyscrapers).
Currently, under the Minimum Energy Efficiency Standards (MEES), landlords in the private rented sector must hold an EPC rating of E or above before granting a new lease. However, the UK government has proposed raising this to a minimum of C by 2030 for all properties.
How long is a commercial EPC valid?
An EPC is valid for 10 years from the date of issue and must be lodged on the national register. Each certificate is accompanied by an EPC report, outlining practical upgrades to improve energy efficiency and cut carbon emissions. A new EPC is only required if the existing one is more than 10 years old.
Where should an EPC be displayed?
An EPC does not need to be physically displayed, but it must be made available to prospective buyers or tenants. In the UK, EPCs are typically provided via an online link, while in Scotland, they are usually issued as printed documents.
Why are non-domestic EPCs useful?
EPCs provide a clear picture of a building’s expected energy efficiency, helping owners, buyers, and tenants understand potential running costs and environmental impact. They highlight areas for improvement through a recommendations report, making them a valuable tool for reducing energy use, cutting carbon emissions, and planning cost-effective upgrades.
Commercial EPCs in Scotland
In Scotland, non-domestic EPCs are required when constructing, selling, or letting a commercial property and remain valid for 10 years. Unlike in the rest of the UK, there is currently no minimum energy efficiency standard for privately rented properties (though this is expected to change).
For buildings over 1000m², Section 63 of the Climate Change (Scotland) Act 2009 applies upon sale or lease. Alongside the EPC, a Section 63 Action Plan must be produced, setting out measures to improve the building’s energy and carbon performance. This plan must be shared with prospective buyers or tenants.
Understanding the Display Energy Certificate (DEC)
Display Energy Certificates (DECs) show a commercial building’s actual energy use over a 12 month period. Unlike an EPC, which is based on a building’s design and fixtures, a DEC is based on real operational data (such as electricity, gas, heating, and cooling). Rated from A to G, the DEC indicates how efficiently the building is being managed day-to-day.
Only a suitably qualified and accredited energy assessor can carry out a DEC survey and issue the report and certificate.
Which buildings need a DEC?
In England, Wales, and Northern Ireland, certain public buildings must obtain and display a Display Energy Certificate (DEC) if they:
- Are occupied by a public body or authority
- Are regularly accessed by the public
- Have a total usable floor space of more than 250m²
How long is a DEC certificate valid?
How long a DEC remains valid is determined by the size of the building’s usable floor space:
- Buildings over 1000m²: DEC certificate must be updated every year
- Buildings between 250–1000m²: DEC certificate remains valid for 10 years
An advisory report must also accompany the DEC, setting out tailored recommendations for saving energy based on the building’s usage patterns. This is valid for 7 years.
Where should a DEC be displayed?
The certificate must be placed somewhere highly visible – typically in the main entrance or reception – so visitors can see it. This helps improve transparency and encourages the person or organisation occupying the building to manage energy use more efficiently.
Why are DECs useful?
Because they are based on real-world performance rather than design specifications, DECs give facilities teams, estate managers, and public authorities an accurate measure of efficiency. They are an essential tool for tracking progress and identifying opportunities to cut energy waste.
DECs in Scotland
Currently, DECs are not used in Scotland. Instead, public buildings over 250m² are required to display an EPC and create an Action Plan detailing how they will lower carbon emissions. This approach supports Scotland’s performance-based approach to improving energy efficiency, but without requiring annual updates or public displays of operational data.
EPCs vs DECs: Key Differences at a Glance
| Aspect | EPC (Energy Performance Certificate) | DEC (Display Energy Certificate) |
| Purpose | Provides a theoretical rating of energy performance, based on the building’s construction and services | Provides an operational rating of energy performance, based on how the building is being run |
| When Required | Required for all non-domestic buildings when being constructed, sold, or let | Required for public buildings larger than 250m² (e.g., council offices, leisure centres, and colleges) |
| Assessor Type | Must be carried out by an accredited non-domestic energy assessor | Must be carried out by an accredited non-domestic energy assessor |
| Validity | 10 years from the date the certificate is produced | 10 years for buildings between 250–1000m²; 1 year for buildings over 1000m² |
| Rating System | A+ (net zero carbon) – G (least efficient) | A (most efficient) – G (least efficient) |
| How It's Measured | Fixed characteristics (e.g., insulation, glazing, heating, lighting, ventilation) | Real data from the past 12 months (e.g., gas, electricity, fuel bills) |
| Display Requirements | No requirement to display publicly (but must be available to prospective buyers/tenants) | The DEC certificate must be clearly displayed where the public can see it (e.g., reception or entrance) |
| Who's Responsible | The property seller or landlord is responsible for ensuring a valid EPC is in place | The person or organisation occupying the property is responsible for ensuring a valid DEC is in place |
| Who Benefits | Useful for prospective buyers, tenants, and landlords assessing a building’s efficiency | Useful for facilities teams, building managers, and the public to understand actual performance |
| Penalty for Non-Compliance | £500–£5,000 fine for failing to make an EPC available to any prospective buyer or tenant | £500 fine for failing to display a DEC at all times; £1000 fine for failing to have possession of a valid advisory report |
Why These Differences Matter to You
Understanding the differences between EPCs and DECs helps you stay compliant and make informed decisions:
- Boost property value – A strong EPC rating can increase market value, attract tenants, and speed up sales or rentals.
- Public accountability – DECs show how efficiently a public building is run, helping organisations demonstrate responsibility, enhance their reputation, and reduce environmental impact.
- Clarity on requirements – Knowing whether your building needs an EPC, a DEC, or both ensures you meet your legal obligations without confusion.
- Cost savings – Both EPCs and DECs highlight opportunities to cut energy use, which can reduce operating costs in the long term.
- Future-proofing – With regulations tightening, having the right certification prepares you for upcoming changes and avoids costly non-compliance.
- Sustainability credentials – Demonstrating energy efficiency can support ESG goals and appeal to investors, stakeholders, and eco-conscious tenants.
- Access to funding – Some grants, loans, or green finance options require proof of energy performance through an EPC or DEC.
How ACI Reports Can Help
ACI Reports has an experienced team of non-domestic Energy Performance Certificate (EPC) and Display Energy Certificate (DEC) assessors, providing detailed DEC / EPC surveys, clear recommendations reports, and expert advice to help you improve the energy efficiency of your commercial properties and stay compliant with regulations.
Not sure whether you need an EPC, a DEC, or both? Get in touch, and we’ll guide you through your obligations.