You’ve just looked at your EPC certificate and felt reassured—your property has a decent rating. But then the energy bills arrive… and they tell a different story.
If you’ve ever wondered why your actual energy usage seems much higher than what your EPC rating predicts, you’re not alone.
The EPC graph is just the beginning. When you know how to read between the lines, your report becomes more than a score—it becomes a blueprint for saving energy, reducing emissions, and increasing property value.
🔍 1. What Your EPC Is (and Isn’t) Measuring
Your Energy Performance Certificate (EPC) is based on a Standard Assessment Procedure (SAP), a theoretical model. It doesn’t track your actual consumption — it estimates energy use under standardised conditions.
What EPC measures:
Property size and insulation
Heating system type and controls
Glazing and ventilation
Construction materials
What it doesn’t measure:
How you use heating/cooling
Number of occupants
Appliance usage
Day-to-day behaviour
🧊 Example: Two identical houses with the same EPC score could have wildly different energy bills if one is home all day with the heat on, while the other is empty 9–5.
⚙️ 2. Standardised Assumptions vs Real-Life Behaviour
The SAP model assumes an average usage pattern. But no two households are the same.
You might:
Work from home (using more heating/electricity)
Prefer warmer indoor temperatures
Have more energy-hungry appliances
These behavioural differences aren’t captured in your EPC.
📊 EPC says: £900/year heating cost
📄 Your bill says: £1,400/year
💡 Reason: The model assumes 19°C rooms and 9-hour heating cycles. You keep it at 22°C all day.
🛠️ 3. Flaws in the Assessment Process
EPC assessments are often visual and assumption-based, not forensic investigations.
Some issues include:
Inaccessible insulation areas (assumed “uninsulated” by default)
Outdated property records
Oversights in listing newer appliances or heating upgrades
Even well-trained assessors are limited by the scope and time of a typical EPC inspection (usually under 2 hours).
🧱 A missed cavity wall insulation upgrade could drop your EPC rating a full band.
💷 4. Fuel Costs and Tariff Volatility
EPCs use national average fuel costs, which might not match your actual tariff.
Let’s say:
Your EPC estimates heating costs based on gas at 10p/kWh
But your actual provider charges 13p/kWh
Multiply that over a year, and the difference can be hundreds of pounds—despite the EPC being technically “correct” for when it was issued.
🔄 5. Aging Certificates = Outdated Data
EPCs are valid for 10 years, but a lot can change in that time:
Your boiler ages or becomes less efficient
Insulation degrades or settles
Your energy usage patterns shift (e.g. family grows)
Unless you get a new assessment, the rating won’t reflect these changes.
🧾 Tip: If your EPC is over 5 years old, it may be time to reassess — especially if you plan to sell or rent.
✅ 6. What You Can Do About It
✔ Understand the EPC’s limits. It’s a guideline, not a guarantee.
✔ Get a second opinion. A private Home Energy Audit can provide real-time usage insights.
✔ Upgrade with bills in mind. Focus on real-world savings, not just EPC score jumps.
✔ Use smart meters. They track your actual consumption, revealing what your EPC can’t.
✔ Consider a fresh EPC. Especially after major renovations or energy upgrades.
📌 Conclusion: EPC = Estimate, Not Exact
Your EPC rating isn’t lying—it’s just not the whole truth.
The disconnect between the EPC graph and your utility bills highlights the gap between standardised models and lived reality.
Understanding these limits helps you make better energy choices and avoid costly assumptions.
Ready to unlock the full story of your EPC?
📅 Book your expert EPC assessment today at EPCrate.co.uk.
The EPC graph might look clear and scientific, but the reality is often much messier.
Let’s dive into why EPC ratings and real-world energy bills don’t always align, and what you can do about it.
