Solar PV can improve a commercial EPC rating, but there is no universal uplift per panel or per kilowatt installed. The result depends on how the building and its on-site generation are represented in the approved assessment method. A PV proposal should be tested against a verified baseline before anyone promises an EPC band.
For owners weighing rooftop solar against a MEES improvement programme, the useful question is not simply whether panels help. It is how much they help this building, which evidence supports the calculation, and whether the investment also makes sense for the occupier.
Why on-site generation can affect the EPC
A non-domestic EPC is an asset rating based on calculated carbon emissions for standardised building use. The Government guide explains that the calculation considers heating, ventilation and lighting, with allowance for energy-generation technology installed in the building. It is not an assessment of the current tenant’s electricity bills.
Solar PV generates electricity on site. When eligible generation is correctly represented in an approved SBEM or Dynamic Simulation Modelling assessment, it can reduce calculated emissions and improve the EPC score. The assessor must use the relevant methodology and evidence: a supplier’s annual yield estimate is not itself an EPC calculation.
Start with the building, not a promised EPC band
Before sizing PV to reach a target, check the existing EPC model. Fabric, glazing, lighting, heating, cooling and controls all affect the baseline. Missing specifications can lead to default assumptions; new evidence may change the starting point in either direction.
Ask the assessor to compare a verified baseline, the proposed PV installation, and a combined option including appropriate demand-reduction measures. Keep the assumptions consistent so the effect of each intervention is visible. For complex buildings, an accredited assessor can determine whether Level 5 DSM modelling is needed; DSM is not a guaranteed route to a better band.
The evidence your EPC assessor needs
Provide the array layout and installed capacity, module and inverter specifications, orientation, inclination and shading information, and documents showing how the system connects to the assessed building. For an existing array, include commissioning records and as-built details where available.
For multi-let buildings or shared arrays, discuss the assessment boundary and allocation of generation early. Do not assume every unit can claim the full output of the same rooftop system. Ownership, wiring and the applicable calculation rules need checking. A PPA or off-site renewable tariff should not be treated as equivalent to a PV installation represented in the building’s EPC.
EPC improvement is not the same as bill savings
An operational business case considers when the building uses electricity, how much generation can be consumed on site, export arrangements, tariffs, installation costs and maintenance. Those factors can make solar valuable even where its effect on the EPC band is modest.
Conversely, an improved modelled rating does not guarantee the occupier will achieve the installer’s savings estimate. Compare the EPC option study with a separate yield and financial assessment using the site’s actual demand profile. Our solar PV consultancy and commercial EPC service can assess those two questions together.
Use PV within a MEES plan, not instead of one
For non-domestic rented property within the MEES regime in England and Wales, the current minimum remains EPC E, subject to applicable exclusions and registered exemptions. Proposed future standards should be treated separately from today’s letting requirements. See our MEES guidance for the wider portfolio context.
A favourable proposed-model result is not a lodged certificate. Complete the works, document what was installed and arrange an appropriate reassessment before relying on a new rating. PV also does not remove separate Part L requirements for fabric and building services where building regulations apply.
If you have a borderline EPC, send us the certificate and roof information. We can scope an evidence review and option assessment without promising an unsupported rating change. General guidance only; site-specific assessment is required.
Frequently asked questions
- How many EPC bands will solar panels add?
- There is no fixed number. The effect depends on the building, array and approved calculation method. Test the proposal in the building model before committing to a target.
- Can proposed panels be counted as already installed?
- A proposed scenario can be modelled for planning improvements, but it is not evidence that the existing building has that performance. The final assessment must reflect the installation and applicable assessment rules.
- Does an EPC show actual electricity savings?
- No. It is a modelled asset rating using standardised conditions. Actual savings need a separate assessment of demand, generation, tariffs and export.
- Can solar alone make a building MEES compliant?
- It may contribute enough in some cases, but only a site-specific assessment can establish the outcome. Check the final lodged rating and any other relevant legal requirements.
Source: GOV.UK — Guide to non-domestic Energy Performance Certificates