Resource
26 May 2026
Understanding which energy certificate commercial buildings need can be confusing, especially when acronyms such as EPC and DEC are used across compliance, property, facilities and sustainability conversations.
Both Energy Performance Certificates and Display Energy Certificates help organisations understand building energy performance. However, they measure different things, apply in different circumstances, and support different decisions.
An Energy Performance Certificate, or EPC, assesses the intrinsic energy performance potential of a building. A Display Energy Certificate, or DEC, shows how a building performs in practice, based on actual energy consumption. In simple terms, an EPC looks at the building’s potential efficiency, while a DEC reflects how efficiently it is being operated.
At Zenergi, we help organisations understand their compliance responsibilities, improve building performance and identify practical steps to reduce energy consumption, costs and carbon emissions.
An Energy Performance Certificate is a document that assesses the energy efficiency of a building. It gives the building a rating from A to G, where A is the most efficient and G is the least efficient.
For commercial buildings, EPCs are required when a building is constructed, sold or let. An EPC is required by law on construction, let or sale of a commercial building over 50m². Each EPC should be logged on the Government Central Register.
A commercial Energy Performance Certificate helps building owners, landlords, developers, managing agents and tenants understand the energy performance of a property and identify improvement opportunities.
Here is the Energy Performance Certificate explained in practical terms: an EPC measures how energy efficient a building is expected to be, based on its fabric, systems and services.
It considers factors such as heating, lighting, insulation, building services and energy sources. Commercial EPCs use a letter scale from A to G, with numeric scores helping businesses understand where a property sits within each band.
A better EPC rating can support compliance, reduce exposure to inefficient buildings, improve marketability and highlight where upgrades may deliver value. EPC recommendations can help identify changes that support long-term energy efficiency and sustainability.
A Display Energy Certificate provides an energy efficiency rating for public buildings based on actual energy consumption data.
Unlike an EPC, which looks at the building’s potential performance, a DEC reflects operational performance. It shows how much energy the building uses in practice, which makes it especially useful for building operators, estates teams and facilities managers.
DECs offer a standardised way to measure and display energy performance, helping public buildings benchmark improvements, support compliance and make better operational decisions.
A Display Energy Certificate can also support wider energy management by making performance visible and helping teams identify whether changes to controls, equipment, behaviour or building use are improving efficiency.
The main difference between a DEC and an EPC is what they measure. An EPC and a DEC both assess building energy performance, but they serve different purposes. An EPC measures the intrinsic or potential energy performance of a building, based on factors such as building fabric, systems, services and modelled performance.
It is typically relevant when a commercial property is constructed, sold or let, and provides an A-G energy rating alongside recommendations for improvement. EPCs are mainly used by landlords, building owners, developers, managing agents, buyers and tenants, helping to support compliance, property value, leasing readiness and improvement planning.
A DEC, by contrast, measures actual operational energy use based on real energy consumption data. It is most relevant to public building operation and energy management, providing an operational energy rating for display and benchmarking. DECs are mainly used by public sector estates teams, facilities managers and building operators, helping to support compliance, operational visibility, benchmarking and ongoing performance improvement.
For organisations managing property portfolios, EPCs and DECs can work together. EPCs help identify the building’s theoretical performance potential, while DECs help show whether day-to-day operation is achieving efficient outcomes.
The right energy certificate commercial buildings require depends on the building type, use and transaction status.
You are likely to need an EPC if a commercial building is being built, sold or let. EPCs are also useful when planning improvements, assessing asset performance or reviewing the long-term value of a property.
You may need a DEC if you operate a qualifying public building where energy performance must be displayed and managed using actual consumption data. DECs are especially relevant where energy use, public accountability and operational efficiency are priorities.
If your organisation manages a mixed estate, you may need both. For example, an EPC may be required for a leased commercial property, while a DEC may apply to a public building where operational performance is displayed.
A commercial Energy Performance Certificate is more than a compliance document. It can help organisations understand where a building is inefficient, where improvements may be needed, and how energy performance could affect value, tenant risk and future regulation.
EPCs can affect rental and saleable value, and can also help reduce tenants’ risk and exposure to rising energy costs. There are also a number of commercial benefits including regulatory compliance, lower operating costs and stronger sustainability credentials.
A clear resource can help stakeholders move from “Do we need one?” to “What can we do with the results?”
A DEC helps organisations understand actual building energy use. That makes it valuable for facilities and estates teams who need to reduce waste, manage operating costs and demonstrate progress.
Zenergi’s BMS and DEC guide explains that Building Management Systems can support better DEC ratings by monitoring, managing and optimising energy usage. It also notes that BMS technology can provide real-time data, support automated controls and help reduce energy consumption during non-operational hours.
This makes the display energy certificate particularly useful as part of an active energy management strategy, rather than a one-off compliance task.
How can you improve EPC and DEC performance?
Improving performance starts with understanding whether the issue is the building’s potential efficiency, its operational use, or both.
For EPC improvements, Zenergi’s resources identify measures such as lighting upgrades, insulation improvements, HVAC upgrades, heat pumps, renewable energy systems and commercial energy audits.
For DEC improvements, operational control is often key. Zenergi’s DEC/BMS resource highlights the role of BMS technology, real-time monitoring, customised control settings, scheduling and data-led optimisation.
The best results often come from combining compliance expertise with practical energy management, so recommendations are not only identified but also prioritised and implemented.
Energy certificate costs can vary depending on the type of certificate, building size, complexity, location, data availability and whether additional modelling, surveys or consultancy are required.
For example, a straightforward EPC for a smaller commercial property may involve a different level of work from a complex portfolio, new-build assessment, optimisation EPC or DEC improvement programme.
Because energy certificate costs depends on the building and the level of support required, the most reliable route is to request advice based on your property, compliance need and improvement objectives.
Zenergi supports organisations with energy compliance, building performance and long-term sustainability.
For EPCs, Zenergi can help certify real estate quickly and efficiently, with follow-on consultation on improving property energy performance.
An EPC assesses a building’s potential energy performance based on its fabric, systems and services, while a DEC shows actual operational energy use based on consumption data.
EPCs are typically needed when commercial buildings are constructed, sold or let, whereas DECs are mainly used for public buildings to support compliance, benchmarking and ongoing performance improvement.
