1. Understanding what drives EPC ratings
An EPC rates a building’s energy efficiency from A (most efficient) to G (least efficient). The rating is based on:
- Heating — How the building is heated, and how efficiently
- Hot water — How hot water is generated
- Lighting — Lighting efficiency and controls
- Building fabric — Insulation, glazing, airtightness
- Cooling — If air conditioning is present, its efficiency
- Renewable energy — Any on-site generation
The rating compares your building against a notional reference building. Improvements to any of these elements can raise your rating.
2. The most impactful improvements
Not all improvements are equal. Some deliver significant rating improvements; others make marginal difference. Here’s what typically delivers the biggest gains:
Heating system upgrades
Heating is usually the biggest energy consumer in commercial buildings. Upgrading delivers major impact:
Boiler replacement
- Old boilers (15+ years) are often 70-80% efficient
- Modern condensing boilers achieve 90%+ efficiency
- Rating impact: Often 5-15 points, potentially one or two rating bands
Heating controls
- Adding or upgrading zone controls, programmable thermostats, weather compensation
- Relatively low cost with meaningful impact
- Rating impact: 3-10 points depending on current setup
Heat pumps
- Air source or ground source heat pumps can dramatically improve ratings
- Higher capital cost but significant efficiency gains
- Rating impact: Can be substantial, especially replacing electric heating
Lighting upgrades
Lighting improvements are often the most cost-effective path to EPC improvement:
LED replacement
- Replace fluorescent and halogen with LED throughout
- Typically 50-70% reduction in lighting energy use
- Rating impact: 5-15 points depending on building type and lighting proportion
Lighting controls
- Occupancy sensors, daylight dimming, time controls
- Reduce lighting energy when spaces are unoccupied
- Rating impact: 3-8 points
Combined lighting upgrade
- LEDs plus controls together often deliver best value
- Quick installation with minimal disruption
- Rating impact: 10-20 points in lighting-heavy buildings
Building fabric improvements
More disruptive and expensive, but permanent improvements:
Roof insulation
- Often the most cost-effective fabric improvement
- Relatively easy to install (especially on flat roofs)
- Rating impact: 5-15 points depending on current insulation level
Wall insulation
- Cavity wall insulation (if applicable) — relatively straightforward
- External wall insulation — expensive but effective
- Internal wall insulation — loses floor space but may suit some buildings
- Rating impact: 5-20 points depending on wall type and current insulation
Glazing
- Upgrade to double or triple glazing
- Significant cost but improves comfort as well as rating
- Rating impact: 5-15 points depending on glazing area and current specification
Draught-proofing
- Seal gaps around windows, doors, service penetrations
- Low cost with noticeable impact
- Rating impact: 2-5 points
Renewable energy
Adding on-site generation can significantly boost ratings:
Solar PV
- Roof-mounted panels generate electricity
- Reduces imported energy
- Rating impact: Depends on system size and building consumption, but often 5-15+ points
Solar thermal
- Panels generate hot water
- Complements rather than replaces main heating
- Rating impact: 3-8 points
3. The improvement pathway
Moving from E to C (or C to B) typically requires combining multiple improvements:
Example: Office building rated E (45)
Target: C (55+)
| Improvement | Est. Rating Impact | Cost |
|---|---|---|
| LED lighting throughout | +8 | ££ |
| Lighting controls | +4 | £ |
| Boiler replacement | +10 | £££ |
| Heating controls upgrade | +5 | ££ |
| Roof insulation top-up | +6 | ££ |
| Total | +33 → Rating 78 (C) |
This is illustrative — actual impacts depend on building specifics. But it shows how combining measures achieves step-changes in rating.
4. Getting an improvement assessment
Don’t guess which improvements will work for your building. Get a professional assessment:
Energy assessment
An energy assessor models your building and identifies which improvements would deliver rating improvements. They can show:
- Current rating breakdown (what’s driving inefficiency)
- Improvement options with expected rating impact
- Cost estimates and payback periods
- The route to your target rating
Why this matters:
Every building is different. LED lighting delivers huge gains in a lighting-heavy retail unit; minimal impact in a warehouse. Heating improvements matter most where heating dominates. The assessment tells you where your specific building needs attention.
5. The 7-year payback test
Under MEES, you must carry out improvements that pay back within 7 years through energy savings. Understanding payback helps prioritise:
Quick payback (1-3 years):
- LED lighting
- Lighting controls
- Basic heating controls
- Draught-proofing
Medium payback (3-7 years):
- Boiler upgrades
- Roof insulation
- Solar PV (depending on electricity costs)
Longer payback (7+ years):
- Wall insulation
- Glazing replacement
- Major fabric works
MEES requires you to do everything with <7 year payback. Beyond that, exemptions may apply.
6. Practical considerations
Tenant cooperation
Many improvements require access to occupied space. Plan works around tenant operations, or coordinate with lease events.
Listed buildings
Heritage constraints may limit options. External insulation, replacement windows, and solar panels may require consent. Plan for longer timescales.
Building use
Improvements should suit how the building is used. High-efficiency heating controls are pointless if the building is unoccupied half the time anyway.
Maintenance access
New systems need maintaining. Ensure access for servicing and eventual replacement.
Combined works
If you’re planning refurbishment anyway, incorporate energy improvements. The marginal cost is lower than standalone projects.
7. Costs and funding
Energy improvements require capital investment. Consider:
Energy savings
Improvements reduce running costs. Factor savings into the investment case.
Enhanced Capital Allowances
Some energy-efficient equipment qualifies for tax relief. Check current eligible products.
Green finance
Some lenders offer preferential rates for energy improvements. Explore green loan options.
Incentives
Check for current government or utility incentives. These change over time but may support certain improvement types.
Increased value
Better EPC ratings support better rents and valuations. This offsets capital cost.
8. Proving the improvement
After works complete, you need a new EPC to demonstrate the improved rating:
- Commission a fresh EPC assessment
- Provide evidence of works completed
- The assessor verifies improvements and issues new certificate
Keep records of what was installed — specifications, completion certificates, commissioning records. These support the EPC assessment and demonstrate quality.
Key Takeaways
- Heating and lighting deliver the biggest gains for most buildings
- Combine multiple improvements to achieve step-changes in rating
- Get a professional assessment — every building is different
- Consider payback — quick-payback items are mandatory under MEES
- Plan around tenants — coordination matters for occupied buildings
- Get a new EPC after works complete to prove the improvement
Need Help?
If you need to improve your property’s EPC rating, we can help. Working with our energy assessment partners Carbon Profile, we provide assessment, specification, and managed delivery of improvement works.
Related Services:
- MEES Compliance & EPC Improvement Works — Full service from assessment to certification
- Contract Administration — Managing improvement works delivery
- Planned Maintenance Schedules — Integrating energy improvements into maintenance planning
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