If your property has been rated D, E, F, or G — you are not alone. Millions of homes across the UK sit in those bands, and many landlords and sellers are under pressure to move up. The good news is that improving your EPC rating does not always mean a full retrofit or a five-figure spend. Many of the highest-impact changes cost very little and can be done in an afternoon.

This guide covers every practical, affordable step you can take to improve your EPC score — from replacing a lightbulb to understanding when a bigger investment pays off. We have written this based on the assessments our team at EPC Rate carries out across London every day.

What actually affects your EPC score

Before spending a penny, it helps to understand what the assessor is actually measuring. An Energy Performance Certificate is calculated using the Standard Assessment Procedure (SAP) — a government methodology that rates your home on energy efficiency and CO₂ emissions on a scale of 1 to 100. The score is then converted into a letter band from A (most efficient) to G (least efficient).

The SAP calculation weighs up five main factors: your heating system, insulation levels, hot water system, lighting, and any renewable energy generation. Glazing, draught-proofing, and heating controls also contribute. Crucially, improvements in any of these areas are reflected in a new assessment — so changes you make before your next assessment will be counted.

“Most London properties I assess are D or E. In almost every case, there are at least three cheap changes the owner could make before I come back for a reassessment.” — EPC Rate assessor, South London

Quick wins under £50

Let’s start with the changes that cost almost nothing but are still recorded by an assessor.

• Switch all remaining halogen or incandescent bulbs to LED
• Fit a hot water cylinder jacket (if you have an older uninsulated tank)
• Install a programmable or smart thermostat
• Seal gaps around doors, windows, and letterboxes
• Add thermostatic radiator valves (TRVs) to individual rooms
• Lag exposed hot water pipes in the loft or under the floor

Lighting upgrades

Lighting accounts for around 15–20% of a typical home’s energy use, and it is one of the easiest wins on an EPC. The SAP methodology specifically records whether your property has low-energy lighting in 100% of fixed outlets. If even one halogen fitting remains, it is counted as inefficient.

Replacing all fixed light fittings with LED equivalents is cheap — a pack of six LED bulbs costs around £8–£12 at most hardware shops — and it can add 1–3 SAP points. That may not sound like much, but for a property sitting just below a band boundary, it can make a real difference.

What counts as low-energy lighting?

LED bulbs, compact fluorescent lamps (CFLs), and fluorescent tube fittings all count. Halogen spotlights — even low-voltage ones — do not. Make sure you replace the fittings, not just the bulbs, where halogens are built in.

Draught-proofing

Draught-proofing is one of the most cost-effective improvements you can make, and yet it is consistently underestimated. A draughty older Victorian terrace — common across London — can lose a significant proportion of its heat through gaps around window frames, under doors, through unused fireplaces, and around pipework where it enters from outside.

• Self-adhesive foam tape around window and door frames (from £3 a roll)
• Brush or rubber strips along the bottom of external doors (from £8)
• Chimney balloon or draught excluder for unused fireplaces (from £20)
• Expanding foam or silicone sealant around pipes and cables entering the property

Draught-proofing will not directly add a large number of SAP points by itself, but it reduces air permeability — a metric that feeds into the calculation and also reduces your heating demand, lowering your energy bills in the process.

Heating controls

Heating system controls are weighted heavily in the SAP methodology. A property with no thermostat, no programmer, and no thermostatic radiator valves will score significantly lower than the same property with all three — even if the boiler itself is identical.

Programmable room thermostat

A basic programmable thermostat allows you to set different temperatures at different times of day. This is assessed differently from a simple on/off thermostat. Adding one can contribute up to 3 SAP points depending on your current setup.

Smart thermostats

Devices like a Hive or Nest thermostat are counted as time-and-temperature zone controls in the SAP methodology, which is the highest category. They cost £100–£250 installed, but the SAP improvement can push a D-rated property into C territory when combined with other changes.

Thermostatic radiator valves (TRVs)

If you have radiators without TRVs, fitting them costs roughly £8–£20 per valve. An assessor will record whether your property has no controls, basic controls, or full zone controls. Moving up a category here can add several SAP points.

Low-cost insulation

Insulation has the largest single effect on your EPC score. For many London properties, particularly Victorian and Edwardian terraces, the biggest gains come from:

Loft insulation

If your loft is accessible and not yet insulated to 270mm depth, this is the single most impactful improvement available. Costs range from free (via the ECO4 government scheme, for eligible households) to around £300–£600 for a typical terraced house if you pay privately. The SAP improvement can be 5–10+ points, often enough to jump a full band.

Floor insulation

Suspended timber floors — common in pre-1930s London homes — lose a significant amount of heat. Insulating beneath the floorboards using mineral wool or rigid boards can add several SAP points. If you are already having other work done and the floor is being lifted, this is a cost-effective addition.

Cavity wall insulation

Properties built after the 1930s often have cavity walls that may be uninsulated. A cavity wall survey costs around £100–£200, and the insulation itself typically runs £400–£1,000 — though again, ECO4 grants may be available. The SAP impact is significant: often 5–8 points and sometimes a full band improvement.

Hot water cylinder jackets

If your property has a hot water storage cylinder that is not already factory-insulated (i.e., a bare copper cylinder), fitting an insulating jacket is one of the cheapest improvements you can make — and it is directly assessed. A cylinder jacket costs around £15–£30 and can add 1–2 SAP points. It also saves money year-round by reducing heat loss from the water tank.

The SAP methodology distinguishes between: no jacket, a thin jacket, a 25mm jacket, and a 50mm+ jacket. If you already have one, make sure it is in good condition — torn or poorly fitted jackets are recorded as partially effective.

Bigger improvements worth considering

Some improvements cost more but deliver the largest jumps in EPC band, and they are often necessary for properties rated E, F, or G. Here is a quick overview:

None of these are “cheap” in the conventional sense, but some — like a new boiler replacing a system that is 15+ years old — deliver both the EPC improvement and meaningful ongoing energy savings. Check the government’s ECO4 and Great British Insulation Scheme to see whether you qualify for subsidised work.

Does solar PV improve your EPC rating?

Yes — solar photovoltaic panels improve your EPC rating, sometimes significantly. The SAP calculation assigns credit for renewable energy generation, and a 3–4kW solar array on a south-facing roof can add 5–12 SAP points depending on your starting score and the property’s energy demand profile.

The improvement is greater for smaller properties with lower overall energy demand, and it is less impactful if the property already has major insulation deficiencies (because the solar generation does not offset poor fabric performance). In most cases, fixing insulation before adding solar gives you the best overall result.

When to book a reassessment

Once you have made improvements — even cheap ones — the only way for them to count is to have a new EPC assessment carried out. Your old certificate will not update automatically. If you have replaced your lighting, fitted TRVs, added a programmable thermostat, and draught-proofed your doors and windows, those changes need to be recorded by a fresh assessment before they benefit your rating.

At EPC Rate, we carry out reassessments across all London boroughs, typically within 24 hours and with the certificate issued on the same day. Our pricing starts from £59 for a one-bedroom property.

We would recommend booking a reassessment once you have completed at least three of the improvements listed in this guide, particularly if your current rating is close to a band boundary. Our assessors can also advise on the spot about which remaining improvements would have the most impact before your next assessment.