Can installing a heat pump lower your EPC rating?

The same certificate carries a second figure. All EPCs also have an environmental rating, and this rating will always improve dramatically if you switch from gas to a heat pump, while the main EPC rating is likely to stay roughly the same and could end up slightly lower or higher². So the answer depends on which number is being read, and on which number the rule in front of you refers to.

For a household, this matters most where an EPC band is a legal threshold rather than a piece of information: the private rented minimum standard, grant eligibility, and the tariff a solar installation attracts. The sections below set out the mechanism, the scale, the landlord rules, the exemptions, and the reform that may change the calculation.

How EPC ratings work: the A to G scale and what the score measures

An EPC rates how energy efficient a building is, with ratings from band A (very efficient) to band G (inefficient)⁷. The same scale is described in Scottish guidance as ranging from "A" (very efficient) to "G" (very inefficient)⁸, and in local authority guidance as an A to G scale with G being the least energy efficient⁹. The band is a summary of a modelled score, not a measurement taken in the home.

What sits underneath that score is the crux of the heat pump question. EPC ratings are based on the costs of home heating, rather than its carbon footprint, which means that cheaper heating scores better¹. A fuel that costs less per unit of delivered heat will therefore flatter the rating, regardless of the emissions it produces. That is why the certificate can reward a gas boiler over an electrically driven heat pump even where the heat pump delivers more heat per unit of energy input.

The certificate is not only a band. Each EPC comes with a report setting out cost effective measures to improve energy efficiency and the energy rating, such as low energy bulbs or upgrading insulation¹⁰. The recommendations report provides more detailed information about improvement measures¹¹. Those recommendations are modelled from the same cost assumptions as the band itself, so a recommendation to switch heating fuel will be judged on running cost as well as on carbon.

Scotland has consulted on replacing the single headline figure. Its proposed domestic rating would use a Heat Retention Rating on an A to G scale, showing a current and potential rating, alongside a Heating System Rating and an Energy Cost Rating¹². That structure separates the fabric of the building from the heating equipment and from the running cost, which is precisely the separation the current single band does not make.

Why the cost-based calculation penalises heat pumps

The mechanism is straightforward once the cost basis is accepted. The price of electricity is inflated by environmental and social levies, with the result that a heat pump can be more expensive to run than a gas or oil boiler¹³. The Public Accounts Committee put the same point plainly: electricity prices mean that heat pumps can be more expensive to run¹⁴. Where the rating follows running cost, a more expensive fuel loses.

Independent analysis has been blunt about the consequence. EPCs continue to favour intensive gas heating over low carbon technologies such as air source heat pumps, owing to the focus on energy costs within the current Energy Efficiency rating¹⁵. The Energy Systems Catapult's finding is that the certificate is working against the direction of travel rather than with it.

The penalty is not automatic, and it is not the same in every home. Croydon Council's retrofit guidance notes that if a home is not well insulated, installing a heat pump may increase energy bills instead, because electricity is more expensive than gas¹⁶. In a poorly insulated home the coefficient of performance can drop to around 2 or even lower units of heat per unit of electricity¹⁷, which narrows or reverses the running cost advantage a well-installed system would have.

Cold weather compounds it. During winter, the air temperature can drop by 5°C or more overnight, which reduces the heat pump's efficiency because it is heating water to a high temperature¹⁸. Lowering the flow temperature reduces the reaction time of the heating system and has a big impact on running costs¹⁸, so the way the system is set up and run feeds directly back into the modelled cost and therefore into the band.

What this means for landlords and the minimum E rating

For landlords, the band is not advisory. Guidance for landlords of domestic, private rented property covers compliance with the 2018 "Minimum Level of Energy Efficiency" standard, EPC band E⁴. In England and Wales the minimum standard of energy efficiency of certain domestic rented property is a rating of E or above¹⁹. Since April 2020, landlords can no longer let or continue to let properties covered by the MEES Regulations if those properties fall below that threshold, unless a valid exemption applies²⁰.

The practical risk is a property sitting at band E on a gas boiler. If a heat pump installation moves the modelled running cost the wrong way, the band can slip to F, and a letting that was lawful becomes unlawful without any change to the fabric of the building. Properties let with an EPC rating of F or G must be improved to a minimum rating of E or an exemption registered where applicable⁴.

The direction of future regulation raises the stakes further. Under the Clean Flexibility Roadmap, landlords will be required to ensure their properties meet a minimum score of EPC C against the fabric performance metric and either the heating system or smart readiness metric, from 1 October 2030²⁰. That is a different test from the current single band, and it is built on the fabric and the heating system rather than on running cost alone.

When you need an EPC and how much one costs

An EPC is required at the point of sale, at the point of a new tenancy, and in various other circumstances set out in official guidance²¹. In Northern Ireland the certificate is administered under its own arrangements²², and Scotland publishes separate guidance for buildings for let²³. The trigger points differ by nation, so the requirement should be checked against the nation the property sits in.

The certificate cannot be produced remotely. An EPC can only be produced by an accredited energy assessor who will visit the property to carry out an assessment¹⁰. Qualified assessors can be found on the EPC register²¹. Online services may handle the booking or store the finished document, but the assessment itself is a visit.

On price, the cost of the EPC will vary from one company to another and you will have to shop around for the best price³. One published figure puts a new EPC at around £60 to £120, depending on the size and location of the home⁴. Size, location and age of the building all bear on what an assessor quotes³.

The band also reaches into other schemes. For solar PV installations wired to provide electricity to a building, the higher tariff rate requires an EPC with a rating of level D or higher at the time of the commissioning date, otherwise the lower rate applies²⁴. The Nest scheme in Wales requires a home to have an EPC rating of 54 (E) or less to qualify⁵. In both cases the band is a gate, and a heat pump that moves it can move eligibility with it.

Could EPC reform fix the heat pump problem?

The case for reform is now made by official bodies rather than by campaigners. The Climate Change Committee has stated that the current EPC rating metrics do not accurately incentivise the energy efficiency and heating solutions required to deliver Net Zero homes²⁵. It has repeated the finding in correspondence on the reform of domestic EPC rating metrics²⁶. The Scottish Government's own review found that EPC ratings do not always capture the true efficiency of a retrofit, noting that measures like PV panels or air source heat pumps may improve an EPC score but fail to address fundamental building issues such as poor insulation or moisture risks²⁷.

The proposed replacement separates the components. Scotland's consultation response sets out a Heat Retention Rating reflecting fabric energy efficiency, a Heating System Rating covering type, emissions and efficiency, and an Energy Cost Rating⁶. Under that structure a heat pump would be judged on the heating system metric for its emissions and efficiency, while the running cost consequence would sit in its own figure rather than dragging the headline band down.

The Committee's conditions for reform are specific. Reforms to EPC rating metrics should be applied alongside wider improvements to the EPC system to improve the quality of assessments and use of data²⁵. Separately, the Parliamentary Office of Science and Technology has noted that reducing the price of electricity relative to gas would make heat pumps more competitive²⁸, which addresses the running cost at source rather than through the metric.

None of this is yet in force for the headline band in England, Wales or Northern Ireland. Until it is, the cost basis stands, and a household or landlord weighing a heat pump against an EPC threshold is working with a rating that measures running cost rather than carbon. For the wider picture of how a heat pump changes a home's exposure to fuel markets and the grid, see heat pumps and household energy independence, and for the equipment itself, air source heat pumps.