If you’re selling or renting a property, you’ll need a valid Energy Performance Certificate (EPC). Most homeowners assume the assessment is complex or disruptive. In reality, it’s straightforward — and there are a few simple things you can do beforehand to ensure the rating accurately reflects your property.

This guide explains what happens during an EPC assessment, easy ways to improve your rating, and what doesn’t affect your EPC (despite common myths).

Key Takeaways

• An EPC assessment usually takes 30–60 minutes.
• Evidence of insulation is crucial — assumptions lower ratings.
• Proof of building changes, heating controls, and insulation levels are important.
• Decoration, appliances, servicing and electrical systems do not affect your score.
• Preparation is about documentation, not cosmetic changes.

What Happens During a Domestic EPC Assessment?

An EPC assessor collects data about the property’s size and layout, construction type, insulation levels, heating and hot water systems, and fixed lighting.

The assessment is non-invasive. No drilling, no lifting floors — only visible evidence and accessible areas such as loft hatches are inspected.

Easy Ways to Improve Your EPC Rating

Provide Proof of Insulation

If insulation is hidden, the software may assume “unknown,” or base levels which lowers the rating. Gather loft insulation invoices, cavity wall certificates, building control sign-off, or dated/GPS stamped photographs taken during installation.

Upgrade to LED Lighting

EPC software rewards properties with a high percentage of fixed low-energy lighting. Replacing CFL, halogen or incandescent bulbs in fixed fittings with LEDs is inexpensive and can improve your score.

Ensure Loft Insulation Is Adequate

Where accessible, around 270-300mm of loft insulation is typically considered optimal within EPC modelling. Topping up low levels can improve performance at relatively low cost. Removing items that are squashing insulation down helps.

Install Heating Controls

Programmers, thermostats, and thermostatic radiator valves (TRVs) improve system efficiency within the EPC model.

Upgrade an Old Boiler

Older non-condensing boilers reduce EPC ratings significantly. Modern condensing systems perform better within the assessment model. You can also consider installing a heat pump.

What Does NOT Matter in an EPC Assessment

• Kitchen quality or appliances
• Portable heaters
• Outdoor lighting or electrical outlets
• Smart meters
• Servicing certificates for heating systems.

An EPC rating is based on building fabric and fixed systems — not the upkeep of these systems.

Local Considerations in Bristol & the BS Postcode Area

Many properties in Bristol are solid wall Victorian terraces, loft-converted homes, or extended properties. These characteristics can significantly affect EPC modelling outcomes.

Providing documentation and ensuring clear access (for example, to loft hatches) helps ensure accurate data capture. If you have added insulation to walls and this is not accessible at the time of the assessment, the assessor may not be able to include this in the assessment.

Frequently Asked Questions

Can I use invoices from building merchants for materials as evidence?

No. DIY insulation projects must be evidenced with a date, and GPS-stamped photos clearly showing the type and thickness (measured with a ruler) of the insulation installed. If the insulation was added by a builder, an invoice showing the builder’s company name, the type and thickness of insulation, the installation date, and the property address is required.

Can you include upgrades that are planned in the future?

No. Assessors are audited based on what can be evidenced at the time of the assessment.

Can I fail an EPC?

No. An EPC is a rating, not a pass/fail certificate — unless you are a landlord subject to minimum efficiency standards and currently fall below an E without a valid exemption.