The cheapest route to EPC C: typical costs and SAP gains
Short answer. The cheapest route to EPC C usually starts with low-cost measures that add the most SAP points per pound: loft insulation, cavity wall insulation, heating controls, a hot water cylinder jacket and LED lighting. For many cavity-walled homes rated D, these together cost a few thousand pounds. Expensive measures such as solid wall insulation (about £12,000 to £15,000), air source heat pumps (around £12,000) and solar PV (around £7,600) come later, if at all. Band C needs a score of 69 on today's EPC scale. Typical SAP gains vary widely by building, so the recommendations on the property's own EPC are the best guide. Ranges here are conservative and sourced.
Most landlords do not need to do everything. They need to do the right few things in the right order. The aim is to reach a score of 69, the bottom of band C on today's EPC scale, for the least money, or to reach the £10,000 cap.
The figures below are typical ranges from the Energy Saving Trust, government sources and EPC industry guides. They are not quotes. SAP gains depend on the building and its starting point. Your property's own EPC recommendations are the best guide. PlutoHome is an introducer to assessors and installers, not an installer.
Where you are starting from
| Band | SAP score |
|---|---|
| A | 92 and above |
| B | 81 to 91 |
| C | 69 to 80 |
| D | 55 to 68 |
| E | 39 to 54 |
| F | 21 to 38 |
| G | 1 to 20 |
Your gap to C is 69 minus your current score. A score of 64 needs 5 points. A score of 45 needs 24 points, which usually means several measures.
Typical costs and gains by measure
| Measure | Typical cost | Typical SAP gain | Best for |
|---|---|---|---|
| Hot water cylinder jacket | £20 to £60 | 1 to 3 | Uninsulated or thinly insulated cylinders |
| LED lighting throughout | £50 to £300 | 0 to 2 | Any home without full low-energy lighting |
| Heating controls | £300 to £700 | 1 to 5 | Wet heating without programmer, thermostat and TRVs |
| Loft insulation to 270mm | £400 to £1,200 | 1 to 8 | Bare lofts or under 100mm |
| Cavity wall insulation | £1,000 to £3,000 | 4 to 12 | Unfilled cavities |
| Suspended floor insulation | £1,400 to £2,500 | 1 to 4 | Suspended timber ground floors |
| Condensing boiler upgrade | £2,500 to £4,000 | 4 to 12 | Old non-condensing gas boilers |
| Double glazing replacing single | £4,000 to £8,000 | 2 to 6 | Mostly single-glazed homes |
| Solar PV, about 4.5kWp | £6,000 to £9,000 | 4 to 12 | Unshaded south, east or west roofs |
| Air source heat pump | £10,000 to £14,000 | 0 to 15 | Electric, oil or LPG heated homes |
| Solid wall insulation | £7,000 to £15,000 | 6 to 15 | Pre-1920 solid walls |
Costs: Energy Saving Trust (February 2026), the government insulation campaign page and older government cost data. Where a source gives a single average, the range is a band around it. SAP gains: EPC industry guides, trimmed to be conservative. See sources below.
A sensible order
- Read your EPC recommendations. They list measures in a suggested order with an indicative rating after each.
- Do the cheap wins. Cylinder jacket, LEDs and heating controls cost little and cause little disruption.
- Insulate the loft and cavity walls if they are not already done. These are often enough to move a D to a C.
- Look at heating. If the boiler is old and inefficient, an upgrade can add many points. Read the warning below first.
- Floor insulation where floors are suspended timber and access is easy.
- Bigger measures such as solar PV, heat pumps, glazing and solid wall insulation only once the cheaper ones are done, and only within the cap.
- Get a new EPC after the work so the improvement is on the register.
A warning about boilers and the new EPC
On today's EPC, a new gas boiler can add useful points. Reformed EPCs, due in the second half of 2027, will add fabric, heating system and smart readiness metrics. A government consultation on the Home Energy Model proposed that it should not be possible to reach EPC C with fossil fuel heating on the relevant metric. That is a proposal, not a decision. The 2030 standard puts fabric first, then lets landlords choose the heating system or smart readiness metric. If you are replacing a boiler anyway, a new boiler is still often sensible. But do not assume it alone secures 2030. Check gov.uk and see our EPC reform guide.
Heat pumps on today's EPC
Today's EPC rating is driven by modelled running costs. Replacing a mains gas boiler with a heat pump can give little or no gain on that scale, and in some cases very little at all. Gains are usually much larger where the existing heating is electric storage heaters, direct electric, oil or LPG. A Boiler Upgrade Scheme grant of up to £7,500 may be available, but it does not count towards the £10,000 cap. Check eligibility on gov.uk.
Typical routes by property type
1930s to 1970s cavity-walled semi, band D
Cavity wall insulation, loft top-up, heating controls and LEDs. Typically about £2,000 to £5,000. Often reaches C.
Victorian solid-walled terrace, band E
Loft insulation, heating controls, cylinder jacket, floor insulation and possibly a boiler upgrade. Solid wall insulation is expensive and may be declined under the new exemption. Many will reach D and then rely on the cost cap exemption, or add solar PV where the roof suits.
Electrically heated flat
Options are often limited by the building. Modern high heat retention storage heaters, a cylinder jacket and LEDs are common first steps. A heat pump may be possible but needs freeholder consent. If consent is refused, the third-party consent exemption may apply.
Mistakes that waste money
- Fitting new windows first. Usually poor value per point.
- Topping up a loft that already has around 120mm or more. The gain is small.
- Paying for measures already recorded on your EPC.
- Not getting a new EPC after works, so the register still shows the old rating.
- Losing invoices. Spend since 1 October 2025 only counts if you can prove it.
Questions
What is the cheapest way to get from D to C?
For most cavity-walled homes: loft and cavity wall insulation, heating controls, a cylinder jacket and LEDs. Typically a few thousand pounds. Your EPC recommendations will show what applies to your building.
How many SAP points do I need for C?
A score of 69 or more on today's EPC scale.
How many points does loft insulation add?
Typically 1 to 8 points. The most where the loft is bare or has under 100mm. A top-up from around 120mm adds very little.
Will a new boiler get me to C?
It can add points on today's EPC. A consultation proposed that EPC C should not be reachable with fossil fuel heating on the relevant new metric. Do not rely on a boiler alone for 2030.
Is a heat pump worth it for EPC purposes?
It depends on the current heating. Gains are usually large for electric, oil or LPG homes and can be small for homes on mains gas under today's EPC.
Are these figures quotes?
No. They are typical ranges from published sources. Get quotes from accredited installers and a fresh EPC assessment.
Sources
- Energy Saving Trust: retrofit explained, average costs (February 2026)
- Government insulation campaign: costs and savings
- Energy Saving Trust: solid wall insulation
- Energy Saving Trust: floor insulation
- Energy Saving Trust: air source heat pumps
- Energy Saving Trust: solar panels
- BEIS domestic cost assumptions (2017)
- EPC Advisor: EPC improvement costs 2026 (SAP gains, commentary)
- Standard Assessment Procedure (gov.uk)