How ECO4 Measures Are Scored and What a Project Must Achieve

ECO4, the fourth Energy Company Obligation, is a scheme worth £4 billion that pays for insulation, heating and renewable measures in homes across Great Britain, and it runs until 31 December 2026 following a nine-month extension¹. What decides whether a particular house gets a package of work is not the house itself but the score that package earns: suppliers are obliged to deliver a set quantity of score, and they choose the homes and measures that generate it most efficiently.

That score is calculated under a methodology fixed in the scheme's legislation. Scores are based on SAP 2012, the standard assessment procedure used for energy ratings, and each measure carries a deemed score drawn from floor area and the home's energy band³. A project must also reach a minimum requirement before it counts in full. Understanding that arithmetic explains a great deal about why some homes are offered a full retrofit and others are declined, and it is set out in full below.

The quick verdict: prioritise the score, then the improvements

The scoring methodology works backwards from what a supplier needs. Each supplier carries an obligation measured in score, and every home it improves delivers a full project score. Full project scores are based on the starting and finishing intermediate SAP bands of the property: the further a package moves a home up the energy rating scale, the more score it generates³.

Individual measures within that package each carry a partial project score. These are pre-calculated, deemed figures based on the floor area of the home and the intermediate SAP band it sits in, so a supplier can work out in advance what any combination of measures will earn³. The scheme's rules require that a partial project score represents a measure's average annual energy bill savings, which is why the score is expressed in pounds per year³.

A worked example from the scoring consultation shows the shape of it. A home with a starting SAP rating of 25 and a total floor area of 80 square metres, brought up through a package of measures that meets the minimum requirement, receives a full project score of 1079.8⁵. The obligation period itself runs from the commencement of the ECO4 Order on 27 July 2022 to 31 December 2026⁶, with suppliers able to deliver early under ECO4 rules and be awarded ECO4 deemed scores from 1 April 2022⁷.

The practical consequence for a householder is that the question is never simply "what does this home need?" but "what package of measures in this home earns enough score?". A home whose starting rating, floor area or fuel type produces a low score may be passed over, even if the need is real. The ECO4 scheme page explains the scheme as a whole, and ECO4 eligibility covers who qualifies in the first place.

Deflator and whole versus partial project scores explained

Three numbers sit at the heart of the methodology: the partial project score for each measure, the full project score for the completed package, and the deflator applied in between.

A partial project score is a deemed figure, fixed in advance, that represents the average annual energy bill saving a measure delivers in a given floor area segment and SAP band³. When a measure treats only part of a property, the partial project score must be multiplied by the percentage of property treated, so a measure applied to half the home earns roughly half the score³.

The full project score is the figure that actually counts towards a supplier's obligation. Scheme rules require that full project scores are based on the difference in average annual bill expenditure between the starting and finishing SAP ratings of the property³. In the consultation example, an internal wall insulation measure with an undeflated partial score of 318.3 pounds per year carries a deflated figure of 191.1 pounds per year, and the completed project meeting the minimum requirement receives a full project score of 1079.8⁵.

The deflator is the mechanism that keeps suppliers honest. All partial project scores are subject to a deflator, applied to maintain the incentive on industry to complete confirmed projects and reach the minimum requirement⁵. A supplier cannot bank the full value of a half-finished job. The final set of partial project scores also includes a correction factor of 10%, a figure that emerged when the methodology was tested against ten example measures developed during consultation, where a correction factor of 6.8% was first suggested³.

Why larger homes earn more: the four floor area bands

Floor area is one of the two variables that set a measure's score, and the methodology segregates scores into four floor area segments³. The reason is arithmetic rather than policy: a measure that saves energy in a large home saves more energy in absolute terms than the same measure in a small one, and the deemed scores reflect that.

The effect is pronounced at the top of the range. Scores for the largest floor area segment, covering homes over 200 square metres, are significantly larger than those for the smaller segments³. A supplier weighing two otherwise identical jobs will earn materially more score from the larger property, and the scoring methodology does nothing to disguise that.

For the example home in the scoring consultation, an 80 square metre property with a starting SAP rating of 25, the segment and band together fix the deemed value of every measure in the package⁵. This is why two neighbours with the same heating system can be offered different outcomes: a modest difference in floor area can move a home into a different segment, and a different starting band changes the score of every measure installed.

The size of these deemed scores matters beyond individual homes. When the methodology was being designed, Ofgem noted that the scores for the largest floor area segment were significantly larger than those for smaller segments, and that the £1 billion spending envelope for the scheme could be breached if the balance of delivery shifted towards larger homes³. The segment structure is therefore both a reflection of physics and a control on the scheme's cost.

What determines the package offered to a household

Several features of the methodology shape which combinations of measures a supplier will put in front of a household.

• Percentage of property treated. A partial project score must be multiplied by the percentage of property treated, so measures that cover the whole home score better than partial ones³.
• Heating system type. SAP differentiates only between combined heat and power and non-CHP district heating systems, and partial project scores were provided for these two scenarios³.
• Heat pump configurations. A specific partial project score exists for shared loop ground source heat pumps in the final scoring matrix³.
• The deflator. Because all partial scores are deflated until the project is completed and reaches the minimum requirement, suppliers have a structural incentive to finish what they start rather than abandon half-installed packages⁵.
• Innovation support. ECO4 includes mechanisms designed to support the delivery of innovative measures where benefits and improvements may not otherwise be captured through the current partial project and full project scores⁸.

Eligibility routes feed into this too. Under ECO4 Flex, an applicant proposing a new targeting methodology under Route 4 must demonstrate, underpinned by evidence, that the methodology is more effective at identifying low income households than the criteria offered under Routes 1 and 2⁹. The ECO4 Flex page covers the routes in detail.

Smart technologies and flexible heating systems are eligible to apply for a new ECO4 measure type and score, but all smart technologies must provide evidence of space heating cost savings⁴. That evidential requirement is itself a driver: a product that cannot demonstrate savings in the approved way will not enter the scoring matrix, however popular it is with households.

Rural off-gas homes, new measures and innovation uplifts

Where the standard scores fail to capture a measure's value, the scheme provides uplifts.

The innovation uplift is the clearest example. A measure approved as an innovation measure can be awarded either a 25% or a 45% uplift, and the uplift is calculated by using the partial project score for the innovation measure⁴. This exists precisely because the deemed scores, built for common measures, understate what genuinely novel products can do.

New measures enter the scheme by two routes: a standard alternative methodology route and a new "data light" route³. The difference in evidential burden between the two routes determines how quickly a product can begin earning score for suppliers, and the methodology for scoring smart thermostats has effect from 14 November 2024¹⁰.

The rural uplift works differently. In the scoring formula, the factor R is 0.2 where the qualifying action is a low-income qualifying action installed at off-gas premises in a rural area in Scotland or Wales, and 0 otherwise¹⁰. In plain terms, a modest score uplift is attached to low-income work in off-gas rural homes in those two nations, recognising that such homes often face the highest costs and the fewest alternatives.

How each UK nation differs

ECO4 is an energy efficiency scheme for Great Britain¹², delivering energy efficiency and heating measures to homes in England, Scotland and Wales¹³. Northern Ireland sits outside it entirely and relies on its own programmes, a point worth checking because households there sometimes search for ECO4 by name.

Within Great Britain, delivery has historically been uneven. Under ECO3, the scheme's predecessor, Scotland received 10.1% of measures and Wales 4.5%¹⁴. Those shares reflect where eligible homes and supplier activity coincided, and the scoring methodology's structure, particularly the floor area segments and the rural uplift, influences where the score is easiest to earn.

The rural uplift itself is nation-specific: it applies only to low-income qualifying actions at off-gas premises in rural areas of Scotland or Wales, not England¹⁰. Off-gas homes in rural England earn no such factor, even where their circumstances are otherwise identical.

There is also a cross-scheme dimension. ECO4 partial project scores are used in the Great British Insulation Scheme to calculate the bill savings a measure achieves¹⁵. The scoring methodology built for ECO4 therefore reaches beyond the scheme itself, and a household weighing GBIS against ECO4 is, in part, weighing two schemes built on the same score.

The regulations that govern the calculations

The methodology is not guidance a supplier can negotiate. ECO4 is enacted by the Electricity and Gas (Energy Company Obligation) Order 2022, as amended¹⁶, and the scoring rules are fixed in legislation. Ofgem stated during the scheme's design that the legislation would require the scoring methodology to be based on SAP 2012, that scores remain based on SAP 2012 unless the legislation is changed, and that the deflator would be part of the scheme legislation in which the administrator has no discretion³.

The technical versions are specified: the methodology uses RdSAP 2012 version 9.94 for reduced-data assessments, and SAP 2012 version 9.92 and SAP 10 for full SAP assessments¹⁷. Band thresholds are expressed to one decimal place³.

The operational documents have evolved alongside the scheme:

The dates matter to households because the rules have moved. The scheme commenced on 1 April 2022²¹, and guidance published in December 2025 required suppliers to complete delivery in full no later than 31 March 2026¹⁶. The original end date was indeed 31 March 2026²², but the scheme was subsequently extended and now runs until 31 December 2026, a nine-month extension¹. A household reading older material about ECO4 deadlines should check the date on it.

ECO4 scoring and its effect on household autonomy

ECO4 funding pays for energy efficiency measures such as heating improvements and insulation to be installed²⁴, with the measures table covering insulation, boilers and central heating, and solar and renewable energy technologies²⁵. For a low-income household, a package that lifts the home several energy bands reduces the energy needed to stay warm, which is the foundation of any household's independence from prices and suppliers.

The scoring methodology, however, tells the household where the limits sit. Solar PV batteries will not contribute to any ECO scoring²⁶, so a supplier has no score-based reason to include storage that would let a home hold its own generation rather than export it. The scheme's focus is on low-income, vulnerable and fuel poor households²⁷, and ECO4's flexible eligibility allows local authorities to identify the most vulnerable households who could benefit from energy efficiency improvements²⁸, but the score still decides what is offered.

The dependence that remains is real. The measures are chosen and funded by an obligated supplier, not the household, and the supplier's choices are driven by what earns score against its obligation. The scheme itself ends on 31 December 2026¹, after which this route to funded work closes. Households weighing ECO4 against other routes can compare it with the Boiler Upgrade Scheme, or read the wider picture in the home energy grants guide, including what grants and energy independence can and cannot deliver.