EPC Rating Estimator — Estimate Your Energy Performance Certificate Band

This EPC calculator gives a quick, indicative estimate of your property's Energy Performance Certificate band using a simplified version of the same principles that drive an official assessment. A real Energy Performance Certificate is produced under the UK government's SAP (Standard Assessment Procedure), applied to existing homes as RdSAP (Reduced data Standard Assessment Procedure). It weighs the building fabric, heating and hot water systems, lighting and any renewables, and returns a single energy-efficiency score from 1 to 100+ that maps to a band from A (most efficient) to G (least efficient).

What this calculator looks at

The tool uses the same headline inputs an assessor records, because these are the factors that move the score the most:

• Property type and age — exposed external surface area and the construction era that signals the likely wall type and built-in insulation
• Floor area — total heated area across all floors
• Wall insulation — cavity fill, internal or external insulation versus uninsulated walls
• Loft insulation — depth of insulation, with 270mm of mineral wool the Energy Saving Trust's recommended depth to meet the Approved Document L (2021 edition incorporating 2023 amendments) roof U-value target of 0.16 W/m²K
• Glazing — single, older double, post-2002 low-E double, or triple glazing
• Heating and hot water — from direct electric (lowest scoring) up to modern condensing boilers and heat pumps (highest scoring)

How the score becomes a band

Each characteristic adjusts a baseline score up or down, and the total is mapped to an EPC band using the standard SAP banding thresholds:

• Band A: 92-100 (very energy efficient)
• Band B: 81-91
• Band C: 69-80 (the confirmed minimum for private rentals from 1 October 2030 under the Warm Homes Plan)
• Band D: 55-68 (around the UK average)
• Band E: 39-54 (the current legal minimum to let)
• Band F: 21-38
• Band G: 1-20 (very energy inefficient)

The estimator also flags the upgrades likely to gain the most points for your inputs, so you can compare options before paying for a survey.

Important disclaimer

This is a rough estimate only and should not be relied upon for legal compliance, property transactions or planning decisions. An official EPC requires a physical inspection by an accredited Domestic Energy Assessor using approved RdSAP software, and is valid for 10 years. Your actual rating may differ from this estimate.