EPC 101: What Impacts a Non-Domestic EPC
Welcome back to our EPC 101 video series, designed to make sense of Energy Performance Certificates for commercial property.
In this episode, we look at what really influences a non-domestic EPC rating. Although EPCs may seem straightforward on the surface, the score you receive depends on far more than a quick walkaround or a tick-box survey. The quality of your building’s fabric, the efficiency of its systems, and the level of detail captured by your assessor all directly affect the outcome.
Watch Episode 3: What Impacts a Non-Domestic EPC
What an EPC Measures
A non-domestic EPC assesses regulated energy use only. That means the calculation includes:
Heating
Cooling
Lighting
Hot water
Pumps and fans
It does not account for unregulated energy such as appliances, small power or industrial processes. As a result, your building’s construction and services have the biggest impact on its rating.
Key elements that influence your score include:
Walls, roofs, floors and insulation
Window and glazing performance
Lighting type and efficiency
Heating, ventilation and cooling systems
Hot water generation
Controls, pumps and fans
The more accurate and detailed the data behind these items, the more accurate your EPC will be.
Understanding Operational Energy: DECs and Energy Surveys
EPCs focus on design intent rather than real-world performance, so they do not reflect how a building is actually used day to day.
If you want insight into a building’s actual energy consumption, Display Energy Certificates (DECs) and energy surveys provide that operational picture.
DECs use metered energy data to show how a building performs in practice over the course of a year
Energy surveys go further by analysing how and where energy is being used, identifying inefficiencies and opportunities for savings
Together they complement the EPC by giving a more complete view of performance, cost, and improvement potential.
Why Assessment Level Matters
Not all buildings are assessed in the same way. The correct EPC level depends on the complexity of the building and its systems.
Level 3: For simple buildings with straightforward services
Level 4: For buildings with more complex HVAC, including full air conditioning
Level 5 (Dynamic Simulation Modelling/DSM*): For buildings with atria, advanced glazing, shading, or features that require hourly simulation modelling
SBEM (used for Levels 3 and 4) checks performance 12 times a year
DSM (used at Level 5) runs 8,760 hourly assessments
DSM does not always produce a higher rating, but it does produce a more accurate one. For many buildings, running both SBEM and DSM gives the clearest overview of performance and compliance risk.
Read more about Dynamic Simulation Modelling here
Why Detail Matters for Asset Value and Compliance
A lower-than-necessary EPC can have real consequences. It can affect lettings, slow acquisitions, reduce asset value and create financing challenges. A strong, accurate rating can support investment decisions, drive portfolio strategy and reduce MEES risk.
That accuracy relies on proper data collection. Manufacturer information, system performance, lighting specifications and fabric details all contribute to the final result. If your assessor is not capturing that level of detail, your EPC may not reflect the true performance of your building.
If you would like tailored advice or want to ensure your EPC accurately reflects your building, our nationwide in-house team of Level 5 DSM assessors can help.
Not sure where your portfolio stands? Book a free 30-minute strategy session with Andy here.