TL;DR:

  • The UK’s EPC system is being reformed with a new multi-metric format replacing the single A-G band, designed to better reflect actual energy costs, carbon emissions, and fabric efficiency separately
  • The old single-band system systematically underrated heat pumps and overrated gas boilers — the new format corrects this
  • Landlords face a minimum EPC C requirement for new tenancies from 2028, with significant financial implications for properties rated D or below

The Energy Performance Certificate has been the UK’s main tool for rating home energy efficiency since 2008. It’s also been widely criticised as misleading — a rating that told you more about the cheapest way to heat a house than how efficient or low-carbon it actually was. A gas boiler in a draughty Victorian terrace could score a C. A well-insulated home with an air source heat pump often scraped a D.

The reform currently working through consultation and implementation is the most significant overhaul since EPCs were introduced. Here’s what’s changing and what you need to know.

What’s Wrong with the Current System

The current A-G rating is calculated using SAP (Standard Assessment Procedure), which weights running costs heavily. When energy prices favoured gas, this made gas boilers look efficient on paper even in poorly insulated buildings. As gas prices rose and heat pump technology improved, the metric increasingly gave misleading signals.

The specific problems:

Heat pumps are penalised. A heat pump using electricity to deliver 3-4 units of heat per unit of energy consumed can score worse than a gas boiler on the current EPC metric, because electricity is priced at a higher rate per unit than gas. The heat pump is demonstrably more energy-efficient, but the cost-based calculation doesn’t capture this.

Fabric quality is hidden. Two houses with very different levels of insulation, window quality, and airtightness can get the same EPC band if they happen to use the same heating system. This doesn’t help buyers understand structural retrofit costs.

Carbon isn’t properly weighted. Gas has a lower cost per kWh than electricity in the current metrics, but a significantly higher carbon intensity. The grid is decarbonising rapidly. A static SAP calculation based on fixed fuel cost factors can’t capture a house’s actual carbon trajectory.

What the New System Looks Like

The reformed EPC introduces a multi-metric format with three separate scores replacing (or supplementing) the single A-G band:

1. Fabric Energy Efficiency (FEE) — measures how well the building itself retains heat, independent of the heating system. Based on insulation levels, window U-values, airtightness, and thermal bridging. This is the metric that tells you how much retrofit the building needs, regardless of what currently heats it.

2. Heating System and Fuel Score — measures how efficiently the installed heating system converts energy to useful heat, and how carbon-intensive the fuel is. Heat pumps score well here. Gas boilers do not, particularly as grid electricity decarbonises.

3. Estimated Energy Cost — a running cost estimate, updated to use current and projected future fuel prices rather than fixed historical rates. This is the metric closest to what the old EPC captured.

The overall headline rating will be derived from a combination of these metrics, with fabric quality given more weight than before. A well-insulated house with a heat pump should score substantially higher under the new system than under the current one.

When This Takes Effect

The timeline has shifted through the reform process, but the current trajectory:

  • 2026: New EPC format finalised following consultation. New EPCs issued from late 2026 will use the updated SAP 11 calculation methodology for the cost and carbon metrics, with full multi-metric reporting phased in.
  • 2027: All new EPCs issued in the reformed format. Properties with EPCs issued before the changeover retain their existing certificate until renewal.
  • 2028: Minimum EPC C for new and renewed tenancies in the private rented sector. This is the deadline that has the most immediate financial implications for landlords.

EPCs are valid for 10 years, so many properties currently have certificates that won’t need renewal until well after the transition. If you’re buying, selling, or letting, check the issue date on your EPC.

What This Means for Landlords

The 2028 minimum C requirement for the private rented sector applies to new tenancies and renewals from April 2028. Properties rated D or below will need to be brought up to EPC C before a new tenancy can start.

Under the current rating system, roughly 55% of privately rented properties in England and Wales are rated D or below. Under the reformed system, some of those will score higher (particularly homes with heat pumps that are currently penalised), but many will still need work.

The government’s permitted cost cap — the maximum a landlord is required to spend before they can claim an exemption — remains a point of debate in the consultation. The expectation is that it will be set at £10,000–£15,000 per property, with exemption available if achieving EPC C would cost more.

Practical implications for landlords rated D and below:

  • Get a current EPC if yours is older than 2–3 years, particularly if you’ve installed solar panels or upgraded heating since the last assessment
  • Understand your property’s fabric issues first: loft insulation, cavity or external wall insulation, and glazing upgrades often deliver the most points per pound
  • If you’re replacing a gas boiler, the timing vis-à-vis the new EPC format matters — a heat pump installed now may score better under the reformed rating than the old one shows

What This Means for Buyers and Homeowners

For buyers, the reformed EPC will give meaningfully more information than the current one. The fabric efficiency score will tell you what the building itself will cost to retrofit, separately from what the current heating system happens to be. Two houses at the same current EPC band but with different fabric scores have very different five-year improvement costs.

For homeowners not facing a regulatory deadline, the reformed EPC changes how improvement decisions should be sequenced. The new system reinforces what retrofit specialists have always recommended: fabric first. Insulating and air-sealing before upgrading the heating system reduces the heating system’s required output and makes any heat pump more efficient. A house with a low fabric score benefits more from wall insulation than from a more efficient boiler.

The Heat Pump Upside

The reform will materially help homeowners who have already installed heat pumps but are sitting on a C or D EPC that doesn’t reflect the upgrade. Under the current system, many heat pump installations — correctly installed, running at COP 3.5+ — still rate lower than a new gas boiler because the electricity price factor dominates the calculation.

The reformed system’s heating system metric will correct this. If you installed a heat pump in the last few years and your EPC doesn’t reflect an improvement, it’s worth getting a new assessment done once the SAP 11 methodology is live — not just for the certificate itself, but for the practical implications if you’re planning to sell or refinance.

Getting Ready Now

Whether you’re a landlord preparing for the 2028 deadline or a homeowner planning improvements, the reform doesn’t change the fundamentals of what makes a home more energy efficient. The improvements that score well under the new system are the same ones that genuinely reduce bills and carbon: insulation, airtightness, glazing upgrades, and low-carbon heating.

What does change is the measurement. A system that better rewards fabric quality and low-carbon heating should send clearer signals to the market about which homes are genuinely efficient — and which are just cheap to run on today’s fuel prices.