Energy Performance Certificates (EPCs) are often misunderstood. Many property owners assume an EPC shows how efficient their home actually is — or how much energy it uses in real life.

In reality, an EPC is a standardised model, not a performance report. It measures certain technical features very precisely — and completely ignores other real-world factors.

Understanding what an EPC does and does not measure helps you interpret your rating correctly, avoid wrong assumptions, and make smarter upgrade decisions.

What an EPC Really Measures

An EPC is based on the SAP (Standard Assessment Procedure) for domestic buildings. It uses fixed assumptions so every property can be compared fairly.

1. The building fabric (how well heat is retained)

The EPC measures:

  • Wall type and insulation (solid, cavity, insulated or not)

  • Roof / loft insulation thickness

  • Floor construction

  • Window type (single, double, triple glazing)

This determines heat loss — the biggest factor in your EPC rating.

2. Heating and hot water systems

The EPC assesses:

  • Boiler or heating system type and efficiency

  • Age and fuel type (gas, oil, electric, heat pump, etc.)

  • Hot water cylinder insulation

  • Presence of smart or programmable controls

Modern, efficient systems score significantly higher.

3. Fixed lighting efficiency

The EPC checks:

  • Percentage of low-energy lighting (LEDs)

  • Lighting type in fixed fittings

This has a smaller impact but still contributes to the overall score.

4. Renewable and low-carbon technologies

The EPC includes:

  • Solar PV panels

  • Solar thermal hot water

  • Heat pumps

  • Biomass systems

These improve your rating even if you personally don’t use much energy.

5. Property size and layout

The EPC model uses:

  • Total floor area

  • Number of storeys

  • Room count

  • Construction age

This affects energy demand calculations and scoring thresholds.

What an EPC Completely Ignores

This is where most confusion comes from 👇

1. How much energy you personally use

Your EPC does not measure:

  • Your actual gas or electricity bills

  • Whether you heat only one room or the whole house

  • Whether you are energy-conscious or wasteful

Two identical homes with identical EPCs can have wildly different bills.

2. Number of occupants

A home with 1 person and a home with 6 people will get the same EPC if the buildings are identical — even though energy use will be very different.

3. Lifestyle and behaviour

The EPC ignores:

  • How often you use heating

  • Shower length or frequency

  • Appliance usage (tumble dryers, gaming PCs, etc.)

  • Working from home energy usage

It assumes an average, standardised household.

4. Energy tariffs or suppliers

Your EPC does not consider:

  • Whether you’re on a cheap or expensive tariff

  • Whether your electricity is green or fossil-based

  • Smart meters or time-of-use pricing

5. Temporary or portable improvements

The EPC ignores:

  • Portable heaters

  • Plug-in air conditioners

  • Draft excluders not permanently installed

  • Temporary insulation solutions

Only fixed, permanent features count.

Why This Matters

Many homeowners panic when:

  • Their EPC is low even though their bills are low

  • Their EPC is high even though their bills are high

This is not a contradiction — it’s because EPCs measure building potential efficiency, not real-world consumption.

When This Causes Problems

Misunderstanding EPCs can lead to:

  • Unnecessary upgrades

  • Wrong investment decisions

  • Disputes with buyers or tenants

  • Confusion about compliance

That’s why professional interpretation matters — not just the number on the certificate.

If you want help understanding your EPC properly or checking whether it reflects your property accurately, EPCrate’s accredited assessors can help:
👉 EPC Assessors London: https://epcrate.co.uk/services-epc-assessors-london/
👉 Book an Assessment: https://epcrate.co.uk/booking/

Final Thoughts

An EPC is a technical, standardised model of your property — not a report card on how you live.

It measures:

  • Fabric efficiency

  • Heating and hot water systems

  • Permanent energy features

It ignores:

  • Human behaviour

  • Energy bills

  • Lifestyle

  • Tariffs

Understanding this distinction protects you from making costly assumptions and helps you use your EPC as the tool it was designed to be — a building efficiency benchmark, not a personal energy judgement.

You can contact EPCrate to review or challenge your EPC if you suspect errors: Contact Us – EPC Services London.

📍 Address: 150–160 City Road, London, EC1V 2NX
📞 Phone: 020 3488 4142
📧 Email: info@epcrate.co.uk