EPC rating C explained

C-rated properties have good energy efficiency, with SAP scores between 69 and 80 points.

What is a C rating?

A C rating on an Energy Performance Certificate indicates that a property has good energy efficiency. Properties with SAP (Standard Assessment Procedure) scores between 69 and 80 points receive a C rating. This places them in the upper third of the A-G scale, above the UK average of D but below the highly efficient B and A ratings.¹

The SAP calculation considers the property's physical features (insulation, glazing, construction) and its heating system efficiency. A C-rated home typically has modern insulation standards, efficient heating, and minimal heat loss through walls, roof, windows, and floors.

How common are C ratings?

According to the 2024 English Housing Survey, approximately 20% of homes in England have an EPC rating of C. This proportion has increased from around 9% in 2015, driven by new building regulations requiring higher standards for new-builds and government schemes encouraging retrofits.²

C ratings are most common in:

• New-build homes from the mid-2010s onwards, when Part L building regulations were tightened
• Retrofitted properties where owners have invested in comprehensive insulation and heating upgrades
• Well-maintained modern homes built after 2000 with original double glazing and cavity wall insulation still intact

By comparison, around 40% of UK homes have a D rating (the current average), 20% have E, and only 5% have reached B or higher.

Energy costs for C-rated homes

Typical annual energy costs for a C-rated property range from £900 to £1,200, depending on property size, location, occupancy patterns, and energy prices. This represents approximately 30-40% lower costs compared to a D-rated home of similar size.³

A three-bedroom semi-detached house with a C rating might cost around £1,050 per year to heat and power, while the same house with a D rating could cost £1,450 or more. Over a 10-year period, that difference amounts to £4,000 in savings.

These figures assume average UK energy prices (as of early 2026) and typical usage. Actual costs vary based on heating behaviour, thermostat settings, and whether occupants are home during the day.

Typical features of a C-rated property

Most C-rated properties share several energy-efficient features:¹

Walls

Cavity wall insulation throughout, or solid wall insulation (internal or external) if built before 1920. No significant cold bridges or uninsulated areas.

Roof

At least 250mm of loft insulation (if pitched roof), or well-insulated flat roof construction. Hatch draught-proofed.

Windows and doors

Full double glazing throughout the property. Modern uPVC or timber frames with low-E glass. External doors insulated and draught-proofed.

Heating

Modern condensing gas boiler (85%+ efficiency) installed within the last 10-15 years, or heat pump. Full heating controls including programmer, room thermostat, and thermostatic radiator valves (TRVs).

Hot water

Well-insulated hot water cylinder with at least 80mm foam jacket, or combi boiler providing instant hot water. Cylinder thermostat and timer controls.

Floors

Insulated suspended floors or solid floors with insulation added during renovation. Less critical than walls and roof but contributes to overall score.

Properties may also benefit from low-energy LED lighting throughout, which adds a few SAP points. Solar panels can push a property from a low C into a high C or even up to B, depending on system size.

Landlord requirements for 2030

The government announced in 2024 that it intends to raise the minimum energy efficiency standard for rental properties from the current E rating to C by 2030. This target applies to all private rented properties in England and Wales, both new and existing tenancies.⁴

Key points about the proposed C rating requirement:

• Timeline: Expected to come into force in 2030 for new tenancies, 2032 for existing tenancies (subject to final regulations)
• Spending cap: Landlords will not be required to spend more than £10,000 to reach C (increased from the current £3,500 cap for E)
• Exemptions: Properties where improvements are not technically feasible or would reduce value by more than 5% may be exempt
• Enforcement: Fines for non-compliance expected to remain at up to £30,000 per property

The regulations have not yet been finalised, and some details may change before they come into force. Landlords with D or E-rated properties should plan ahead, as demand for energy assessors and installers is expected to increase sharply as the deadline approaches.

How to get from D to C

Moving from a D rating (55-68 SAP points) to a C rating (69-80 points) typically requires gaining 5-15 SAP points. The most cost-effective improvements depend on what's already in place, but common upgrades include:⁵

Top up loft insulation

Cost: £300-£500 (DIY) or £500-£900 (professional). Gain: 3-5 SAP points if upgrading from 100mm to 270mm. Quick payback of 2-4 years.

Cavity wall insulation

Cost: £700-£1,200 for a typical house. Gain: 8-12 SAP points if walls are currently uninsulated. One of the highest-impact upgrades available.

Upgrade heating system

Cost: £2,000-£3,500 for a new condensing boiler, or £7,000-£14,000 for a heat pump (with £7,500 Boiler Upgrade Scheme grant). Gain: 5-10 SAP points if replacing a boiler over 15 years old.

Replace single glazing

Cost: £4,000-£8,000 for a whole house. Gain: 6-10 SAP points. Worth doing if windows need replacing anyway, but expensive for SAP points alone.

Add heating controls

Cost: £200-£400 for TRVs and room thermostat. Gain: 2-4 SAP points. Low cost, easy retrofit.

Many D-rated properties can reach C by combining two or three of these measures. For example, adding cavity wall insulation and topping up loft insulation could move a 65-point D-rated house to a 75-point C-rated house for under £2,000.

Your EPC certificate includes a recommendations section that estimates the SAP gain for each suggested improvement. However, these are generic estimates. For a precise assessment, consider commissioning a retrofit assessment from a PAS 2035 Retrofit Coordinator before committing to major works.