Home Energy Assessments: The Types and What Each One Tells You

A home energy assessment is any structured look at how your house uses energy and what could be done about it, and the term covers four quite different things. A free online energy check, of the kind offered by government-backed services, helps you understand how energy efficient your home is and what changes could reduce energy use, and it takes minutes because you answer the questions yourself¹. An Energy Performance Certificate (EPC) survey is a visit by an assessor that produces a standardised rating of your home's energy efficiency². A PAS 2035 retrofit assessment, introduced in 2019 as a framework for best practice in the energy retrofit of domestic properties, looks at the whole building and has to be managed by a qualified Retrofit Coordinator³. A heat loss survey is the most detailed of the four and is used when a new heating system, such as a heat pump, is being designed⁴.

Which one you need depends on the question you are asking. If you want a rough idea of where to start, the online check answers that at no cost. If you want a document that compares your home to a national standard, that is the EPC. If you want a plan for real work on the building, that is the retrofit assessment. And if you are about to replace your heating system, the heat loss survey comes into its own. This page sets out what each route covers, who carries it out, and what it does and does not tell you.

Comparing the four options

The four assessment routes differ in cost, depth and purpose, and it helps to see them together before going into each one.

The routes are not rivals; they sit at different depths. A householder quoted in one council's account of its grant scheme described the sequence plainly: an online application, then a survey of the home to check its energy rating, then a talk through the options and the benefits⁹. That is the typical ladder: check, survey, plan.

No-cost online tools to begin with

The cheapest assessment is the one you carry out yourself. The Northern Ireland Housing Executive's home energy saving tool is typical of the type: it helps you understand how energy efficient your home is and what changes could help reduce energy use¹. Cornwall Council's Homewise tool does the same job, giving energy saving advice to help save money on energy bills and boost the energy rating of the home¹⁰. These tools cost nothing and take minutes, because they work from what you already know about your house: its age, size, heating system and glazing.

What you get is an indication, not a measurement. The tool has not seen your house, so it works from your answers. That makes it useful for ranking ideas, working out which improvements might matter most, and deciding whether a paid assessment is worth commissioning, but it is not a document anyone else will rely on. It cannot see the state of the loft insulation or the draughts around a back door.

Free does not stop at the online tool. In some areas, council-backed schemes go further: Tameside's Local Energy Advice Programme provides a free home visit from a qualified Home Energy Advisor¹¹. South Cambridgeshire's Action on Energy provides communities with advice and support for improving home energy efficiency¹². And the UK Government is consolidating this landscape: a new Home Energy Advice service is planned as a single entry point on GOV.UK, helping homeowners, landlords and tenants find tailored, impartial and trusted advice on how to heat their homes and make them more energy efficient¹³. Qualitative research published in March 2026 explored which sources of advice are trusted, what advice is perceived as most important, and the gaps in provision, which is the evidence behind that consolidation¹⁴.

What the EPC rating covers

An EPC provides an assessment of your home's energy efficiency². It is the assessment most households encounter first, because a certificate is required when a property is built, sold or let, and it is the one most often quoted in estate agent particulars and grant rules.

What the rating measures is narrower than many people assume. The calculation is based on standard assumptions of occupancy and use, and does not take into consideration variations in occupant behaviour or the state of repair⁷. It is a rating of the building as an asset, under standardised conditions, not a forecast of your bills. Both the domestic and non-domestic EPC display estimated annual primary energy use for the property, in units of kilowatt-hours per square metre¹⁵. The domestic certificate also provides a primary energy indicator, which is the amount of energy used to produce one kilowatt of power for the household⁷.

Alongside the rating comes the recommendations report: information on measures which could be made to improve the energy efficiency, with an indication of cost and typical savings for each improvement over 3 years⁷. That report is what turns the certificate from a score into a starting point. Northern Ireland's official advice puts it simply: looking at your EPC is a good starting point to help improve the energy efficiency of your property¹⁶.

The EPC's reach is not total. Around a third of domestic properties in England and Wales do not have an EPC rating⁶, so a home that has not been sold or let in many years may have no certificate at all. If you are planning work, see using your EPC to plan work.

PAS 2035 and whole building assessments

Where the EPC rates the building against a standard, a PAS 2035 retrofit assessment examines it as an individual case. PAS 2035 was introduced in 2019 as a clear framework for best practice in the energy retrofit of domestic properties, and it has to be managed by a qualified Retrofit Coordinator, so the householder does not have to manage the process personally³.

The distinction matters because retrofit work done measure by measure, without a view of the whole building, is where things go wrong: insulation in the wrong order, or a heat pump fitted to a house that was never assessed for it. A whole building assessment goes further still. The Scottish Government's tenement working group proposed that such an assessment should provide information and recommendations to owners on both the energy efficiency measures and zero direct emissions heat systems appropriate for the building as a whole and individual dwellings, and noted it could potentially be used as a basis for regulation⁸. That is the direction of travel: assessment as the foundation on which both insulation and heating decisions are made together.

For householders, the practical difference is depth and cost. The retrofit assessment gathers information about the actual building: its construction, condition, ventilation and occupancy, rather than standard assumptions. It is the assessment that sits behind a whole house plan, and the people who carry it out are described in retrofit assessors and retrofit coordinators. Research into able-to-pay households in Bristol found that potential triggers for installing energy efficiency improvements were other building work (14%) or the heating system reaching the end of its life¹⁷, which is exactly when a whole-building assessment earns its keep: at the moment decisions are already being made.

What happens during an assessment

On the day, the four routes feel very different. The online check involves nobody but you. The EPC survey is a single visit: the assessor walks the property, records its construction, heating, insulation and glazing, and the rating is then calculated using the approved methodology rather than measured directly.

The free home visit from a Home Energy Advisor, where a scheme offers one, sits between the two: it is a conversation in your home with someone qualified, covering how you use it as well as what it is made of¹¹. The retrofit assessment is the most involved visit, because it feeds a whole-building plan rather than a single score. The heat loss survey is the most technical: it gathers the room-by-room data that feeds the heat pump methodology, a calculation methodology designed to assess the energy performance of homes⁴.

What none of these visits involves is disruption. There is no lifting of floorboards or drilling: the assessments are observational and documentary. What the householder supplies matters as much as what the assessor records. Documentation from previous work, warranties and certificates all feed the assessment, which is one reason the site keeps a guide on the paperwork to keep from every energy improvement.

Understanding the assessment data

The national picture gives context for your own rating. Homes in England had a median EPC score of 69, Band C, in March 2025⁵. Around two-thirds of Council or Housing Association houses have the highest EPC ratings A-C, compared to around 40% of houses in other tenure types⁶, so the stock is unevenly improved, and where you start depends partly on what kind of home you live in.

The official statistics that describe this landscape carry their own health warnings. The June 2026 household energy efficiency headline release states that these statistics are provisional and are subject to future revisions¹⁸, a caveat repeated in earlier releases back to 2015¹⁹. The Energy Efficiency of Housing statistics for England and Wales have been discontinued following a review of outputs⁵, so the ONS article of March 2025 is the last of its series. Northern Ireland's energy rating statistics are Official Statistics in Development²⁰, a designation that signals they are still being established. The English Housing Survey energy chapter is accredited official statistics²¹.

The grant schemes that assessments feed into are tracked too. The Green Homes Grant Local Authority Delivery and Home Upgrade Grant statistical releases include analysis on measures installed, homes upgraded, installation rates, installations by region, local authority and parliamentary constituency, carbon, bill and energy savings, and changes in Energy Performance Certificate ratings²². That last item is the one that matters most to a householder: the recorded EPC change is how the system knows an assessment-led plan actually worked, which is the subject of measuring results after the work.

Rules across the UK nations

The assessment types are broadly the same across the four nations, but the advice services that offer them, and the ratings they produce, differ.

In England, the median EPC score of 69 (Band C) in March 2025⁵ sets the benchmark, and around a third of domestic properties in England and Wales do not have an EPC rating at all⁶. Scotland is reforming its certificates: the Scottish Government's EPC reform response establishes a new technical infrastructure to replace the current Standard Assessment Procedure with a new UK-wide methodology²³, and a new Energy Cost Rating will be based on the cost of energy to run the home to standardised conditions, in line with the current Energy Efficiency Rating or SAP Rating²³. Scotland's non-domestic Energy Efficiency Rating will follow the same rating scale as the Asset Rating used in England, Wales and Northern Ireland²⁴, and consultation views on aligning with the rating system used in other parts of the UK were positive²⁴.

Wales and Northern Ireland have their own advice infrastructure. The Consumer Council NI and Northern Ireland Energy Advice give free, independent and impartial energy advice to all domestic householders in Northern Ireland¹⁶. Delivery rates also differ: under the Energy Company Obligation, Scotland saw an average of 118 measures per 1000 households, compared to 81 in Wales and 77 in England, as of December 2020²⁵. The calculation itself is UK-wide: domestic EPCs use a UK-wide calculation methodology managed by the UK Government with input from the devolved administrations⁷. For nation-specific starting points, see free home energy advice in England, Scotland, Wales and Northern Ireland.

How the rating is calculated

The EPC rating is not an opinion. It is the output of a government-approved calculation methodology, and the legal basis is specific: the approved methodologies are set out under regulations 24 and 25 of the Building Regulations 2010 for the calculation of the energy performance of new buildings²⁶.

For dwellings, the methodology is the Standard Assessment Procedure for Energy Rating of Dwellings, SAP²⁷, currently version 10.3 for the energy performance of new dwellings in England²⁶. For buildings other than dwellings, it is the Simplified Building Energy Model, SBEM, used to assess non-domestic buildings²⁷, with the National Calculation Methodology for buildings other than dwellings in England, 2026 version, approved as of 24 March 2026²⁶. The legislation behind the Energy Companies Obligation shows how these versions layer up over time: it defines "Standard Assessment Procedure" as the 2009 Edition, as amended in October 2010, and "Standard Assessment Procedure 2012" as the 2012 Edition, version 9.92²⁸.

What this means for a householder is that the rating on your certificate is reproducible: two assessors recording the same features should reach the same score, because the calculation is fixed. It also means the rating moves when the rules move, not when your house does. A home can score differently under a new methodology with no physical change, which is worth remembering when comparing an old certificate with a new one.

Replacing SAP with the Home Energy Model

The methodology behind domestic EPCs is in transition. The Home Energy Model (HEM) is a calculation methodology designed to assess the energy performance of homes⁴, and the Scottish Government's reform response confirms it is establishing a new technical infrastructure to replace the current Standard Assessment Procedure with the new UK-wide methodology²³.

The changeover will not be abrupt. During the transition, both HEM and a version of SAP will be available for a limited period²⁹, so certificates produced in that window may rest on either methodology. HEM also brings dedicated technical procedures, including a heat pump methodology⁴, which is the calculation that a heat loss survey feeds.

Scotland's reforms also change what the certificate shows. The Energy Cost Rating will be based on the cost of energy to run the dwelling to standardised conditions²⁴, and a proposed Energy Use Rating would inform dwelling owners about the energy use of their property, complementing running costs and carbon emissions, and display how measures and heating systems can reduce energy use⁷. The direction is towards certificates that separate cost, energy and carbon, rather than compressing all three into one letter.

Assessment limits for self-sufficiency

An assessment is the map, not the journey. What it does for a household's energy independence is establish where the home stands, in figures a funder, installer or regulator will accept, and what order work should follow. Without it, improvements are guesses; with it, they are a sequence. The EPC recommendations report, with its indication of cost and typical savings for each improvement over 3 years⁷, is the first version of that sequence, and a PAS 2035 assessment is the full one.

What it does not do is reduce a single unit of energy use by itself. The assessment changes nothing in the fabric of the house. It also does not remove the dependencies that follow: the measures it recommends still come from manufacturers and installers, the heating system still depends on fuel supply or the grid unless the plan goes further, and the certificate itself depends on a government methodology that can change. The EPC's standard assumptions⁷ mean it cannot even tell you how much energy you personally use; for that, see working out how much energy your home uses before you spend.

The honest position is that an assessment is the cheapest step with the longest reach. It costs little or nothing in its online form, it costs a survey fee in EPC form, and it costs professional fees in retrofit form, and every later decision, from grants to payback periods, rests on it. A household that skips it does not avoid the cost of assessment; it spreads the cost of guessing across every improvement it makes.