An Energy Performance Certificate scores a building's modelled energy use — and that score increasingly determines what lenders will finance, what tenants will sign, and what buyers will pay.
An Energy Performance Certificate (EPC) is a government-mandated assessment of how energy-efficient a building is. For commercial properties in England and Wales, the certificate is produced by an accredited assessor using standardised software, resulting in a rating from A (most efficient) to G (least). The rating affects compliance — commercial landlords cannot legally let a property below EPC E — but it also affects valuation, refinancing, and tenant attraction in ways that the statutory minimum alone does not capture.
The score is a modelled figure: it represents how much energy the building would consume if occupied and operated to a standard pattern, not what any particular tenant actually uses. On-site renewable generation reduces that modelled demand from the grid, directly improving the rating.
Commercial EPC assessments are produced using the Simplified Building Energy Model (SBEM) for most non-domestic buildings, or Dynamic Simulation Modelling (DSM) for complex properties such as large mixed-use developments, buildings with unusual HVAC configurations, or where SBEM cannot adequately capture the building's behaviour.
The assessor inputs the building's physical characteristics:
The model calculates an asset rating: a number expressed in kWh/m²/year of primary energy, which is then converted to a letter grade. The rating bands are set nationally and apply uniformly across England and Wales.
The certificate is valid for ten years, but must be renewed whenever a property is let or sold if the existing certificate is more than ten years old. A new certificate must reflect the building as currently configured — changes since the last assessment, including new energy systems, must be assessed.
The distinction between an asset rating and an operational rating matters for understanding what an EPC tells you and what it does not.
An asset rating measures the building's inherent energy performance characteristics — the fabric, the systems, the envelope. It is independent of how any particular occupant uses the building. A warehouse used intensively by a refrigerated logistics company and the same warehouse standing empty would carry the same asset rating.
An operational rating measures what a building actually consumed over a given period, based on metered data. This is the basis for the Display Energy Certificate (DEC) used in public buildings, not the commercial EPC.
The practical implication of the asset rating approach: improvements to the building's inherent energy performance — insulation, system upgrades, on-site generation — improve the EPC rating. Changes in tenant behaviour or operational intensity do not change the certificate.
For landlords, this means the EPC rating is within their control to improve — it is not dependent on tenant cooperation once the infrastructure is in place.
When solar PV or wind generation is installed at a commercial property, the generation is modelled as an offset to the building's grid demand. The SBEM calculation credits the on-site generation against the building's modelled energy consumption, reducing the primary energy figure and improving the rating band.
Battery storage compounds this effect: a battery paired with on-site generation shifts self-consumption from periods of low generation (when grid electricity would otherwise be drawn) to periods when the generation is available. The SBEM methodology accounts for battery storage when calculating the self-consumption contribution to the rating.
The practical result is that a property sitting at EPC C — close to EPC B but unable to reach it through fabric improvements alone — can reach EPC B through on-site generation and battery storage without structural changes. For older commercial buildings where envelope improvements are costly or constrained by planning or heritage requirements, this is often the most cost-effective route.
The on-site generation that improves the EPC rating also produces a continuous energy income: from self-consumption savings, from battery dispatch to grid-services markets, and from the contracted energy rebate paid to the property owner by HNordic. The EPC improvement and the income generation come from the same infrastructure.
Compliance: A commercial property below EPC E cannot legally be let in England and Wales. From 2031, larger non-domestic buildings over 1,000 m² must reach EPC B where improvements are cost-effective. Properties that fall short face enforcement action, civil penalties, and registration of non-compliance on the public EPC register.
Tenant letting: Corporate tenants with sustainability reporting obligations under the Corporate Sustainability Reporting Directive (CSRD) or the UK's Streamlined Energy and Carbon Reporting (SECR) framework require low-Scope-2 premises. A building with a weak EPC rating creates an energy consumption liability in the tenant's own disclosures. Larger commercial tenants are increasingly asking for EPC evidence at heads of terms stage and in some cases requiring minimum EPC standards as a lease condition.
Refinancing: UK commercial property lenders are incorporating EPC ratings into underwriting — requiring minimum ratings at origination and in some cases setting EPC improvement milestones as conditions of drawdown. A property below EPC C faces increasing friction in the refinancing market. A property with a credible EPC B trajectory and documented energy infrastructure investment is treated differently.
Valuation at exit: Commercial properties are valued by capitalising net income at a yield. A building whose EPC position creates compliance risk, tenant friction, or lender pricing premium carries a discount to a comparable building without those exposures. The discount is not a theoretical adjustment — it is realised in transaction pricing and refinancing terms.
An EPC assessor produces the formal certificate. A site assessment by HNordic covers a different question: given this building's current EPC position, what energy infrastructure investment bridges the gap to EPC B, and what does that investment generate in contracted income?
The site assessment maps the property's current asset rating and models the rating improvement available from battery storage, solar generation, and where applicable, wind generation — the same infrastructure that produces the energy income stream. The output is a specification and a business case: the EPC improvement, the contracted rebate to the property owner, and the infrastructure cost, together.
See also: What is MEES and what does the EPC B announcement mean? · Battery storage: backup power versus revenue asset · Full FAQ