How is the EPC rating calculated?

The EPC rating is based on a Standard Assessment Procedure (SAP) calculation that evaluates energy efficiency based on construction, insulation, heating system, hot water, lighting and ventilation. The result is a score from 1–100 mapped to bands A (most efficient) to G (least efficient). The rating reflects the building fabric and systems, not occupant behaviour.

What EPC rating do I need for renting?

Since April 2020, rented properties in England and Wales must have a minimum EPC rating of E. The government has proposed raising this to C for new tenancies (originally from 2025, now delayed). Landlords should aim for at least band C to future-proof their properties.

What are the cheapest ways to improve an EPC rating?

The most cost-effective measures are typically: hot water cylinder insulation (£20–50, +3 points), LED lighting (£100–300, +4 points), draught proofing (£100–300, +3 points), loft insulation (£300–600, +8 points). Cavity wall insulation offers excellent value at £500–1,500 for up to 12 points improvement.

How many points does each measure improve the EPC?

Improvement varies by property but typical gains are: loft insulation 5–10 points, cavity wall insulation 8–15 points, condensing boiler 8–12 points, solar PV 10–18 points, heat pump 12–18 points. The actual gain depends on your property size, existing insulation and heating system.

How accurate are these EPC improvement estimates?

These are indicative estimates based on typical UK housing stock. Actual SAP point gains depend on the specific property, its construction, size and existing features. A full SAP calculation by a qualified energy assessor will give precise figures. Use these estimates for planning and prioritisation.

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EPC Improvement Calculator — Energy Rating Upgrades

Rank energy efficiency measures by cost-effectiveness to improve your EPC rating. See predicted rating improvement per measure with UK-specific costs.

Current EPC band

Current SAP score

Target EPC band

How We Calculate This

This calculator ranks energy efficiency measures by cost per SAP point gained, helping you prioritise investments.

Method

Each measure has a typical SAP point gain and cost range. Measures are ranked by cost per point (lowest first). The calculator selects measures in order until the target rating is reached.

Limitations

Points gains are based on typical properties. Actual results vary — a SAP assessment from a qualified assessor will give accurate predictions for your specific property.

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.