Why Actual System Efficiencies and Lighting Specs Matter in Your EPC
How accurate data collection can make or break a building’s energy performance rating
When it comes to non-domestic Energy Performance Certificates (EPCs), every detail counts. It may be that property owners don’t realise just how much the use of default figures in energy assessments, especially for HVAC systems and lighting, can drag down a building’s rating.
That’s why choosing the right energy assessor matters. At MEES Solutions, we take the time to carry out detailed site surveys, identify key system data, and gather the evidence needed to reflect your building’s true energy performance.
In this blog, we explore the key differences between default figures and actual data in the software, how it affects an EPC, and what steps can be taken to ensure a property’s energy performance is fairly and accurately represented.
SBEM Defaults: What They Are and Why They’re a Problem
When actual performance data for systems like boilers, chillers, air handling units, and lighting isn’t provided, the EPC software defaults to generic efficiency values, typically low to reflect worst-case scenarios.
This means:
● A highly efficient HVAC system may be treated as average /outdated.
● Modern LED lighting systems could be undervalued in terms of their energy efficiency.
● A building’s real-world upgrades might not be reflected at all in the EPC rating.
In short: if an assessor can’t access the evidence, the EPC rating might not be as good as it could be.
Real-World Example: The Default Penalty
Take a typical non-domestic property, an office or retail unit fitted with split air conditioning systems and a modern boiler.
In reality, the AC system might have a seasonal efficiency (SEER) of 4.5, and the boiler may achieve a seasonal efficiency of 90–92%, or even higher. But unless the exact make and model can be identified and supported by documentation, the energy assessor must input default values into the SBEM software of “??” which could drop your EPC rating by one band or more and lead to unnecessary CapEx.
In these cases, even a highly efficient VAV unit could be recorded in SBEM with default seasonal efficiency (SEER) values as low as 2, a huge drop from the real value.
Multiply that across multiple units in a large property, and the result is clear: a building could be rated as far less efficient than it is, simply due to missing or unverified data.
Here's the catch:
Despite doing all they can during the site survey, checking plant rooms, rooftop units, and internal cassettes, assessors are often unable to verify system details.
Why?
● Manufacturer labels are often weathered or worn away, especially on older rooftop units.
● Plant areas may be difficult to access safely.
● Lack of servicing or record-keeping means no datasheets or installation documents are available on site.
Lighting Specifications: The Undervalued Upgrade
Lighting is one of the easiest upgrades to implement, but only if it’s documented correctly. Dfault luminous efficacy values have to be used unless detailed specifications (such as lumens per circuit watt, control types, and zoning) are provided or evidenced. In short, get a Lighting Design and save money.
When LED lighting is selected without detailed manufacturer data, a default luminous efficacy of 50 lumens per circuit watt is assumed. While this may seem adequate, many modern commercial LED systems can be 120–150 lumens per watt. Without providing specific product datasheets or layout information, the system’s actual efficiency is diminished drastically, meaning the EPC misses out on recognising one of the most straightforward and impactful energy upgrades available. This could resultin a need to spend money elsewhere to achieve the rating gains that the new lightingsystem already achieves.
Supplying detailed lighting specifications can significantly reduce calculated energy demand and contribute to a stronger EPC rating.
The Business Cost of Default Values
Using defaults doesn’t just lower arating, it can:
● Undermine the value of recent capital investments in building systems
● Create unnecessary MEES compliance risks
● Affect lease negotiations or asset disposals
● Reduce confidence in abuilding's ESG credentials
Default values don’t just lower the EPC rating, they can cost real money. A lower rating may trigger expensive improvement requirements under MEES regulations, delay lettings or sales, or even lead to legal non-compliance for landlords. For portfolio managers, this can translate into missed ESG targets, reduced asset value, and limited appeal to sustainability-conscious tenants or investors. Inaccurate assessments caused by missing data effectively penalise buildings that are already performing well, simply because they lack detailed information….Which will normally be available somewhere.
What You Can Do: Ensuring Actual Performance Is Reflected
To avoid being penalised by default values, landlords, vendors, and property managers should take proactive steps to ensure their building’s true energy performance is captured accurately in EPC assessments.
1. Maintain a Digital Asset Record
Keep all relevant information, such as system datasheets, commissioning certificates, lighting layouts, and performance specs, in a single, easily accessible digital location. This not only streamlines EPC assessments but also future-proofs thebuildings documentation and property ownership.
2. Carry Out Regular Maintenance on HVAC and Plant Systems
Routine maintenance not only improves operational efficiency but also helps preserve crucial data. Cleaning dirt or debris from data plates ensures that the make, model, and performance information remains visible and usable for assessors during site visits.
3. Work with Your FM or M&E Teams
Facilities Management and Mechanical & Electrical contractors often hold valuable records or have access to systems data. Engage with them early to retrieve technical documentation, maintenance logs, and equipment specifications.
4. Engage a MEES Solutions Energy Assessor Early
Don’t wait until the EPC is due. Involve a MEES Solutions Non-Domestic Energy Assessor as early as possible, particularly during refurbishments, acquisitions, or tenancy changes. We can proactively help identify missing data and guide you on what information to gather in advance.
A Smarter EPC Strategy
An EPC is more than a compliance certificate; it’s a reflection of your building’s ? value and sustainability. Using actual performance data instead of defaults can unlock:
● Better EPC ratings
● Enhance asset value
● Smooth transactions
● Reduce the risk under MEES
● Clear ROI on energy upgrades
At MEES Solutions, we help clients make the right decisions. Our in-depth assessments and guidance provide Common Sense Compliance, ensuring you’re not penalised for a paperwork gap.
Need help improving your EPC rating or preparing your documentation?
Get in touch with our team today to ensure your building gets the rating it truly deserves.