According to the statutory instrument laid before Parliament on 8 September 2026, DESNZ has rewritten the Warm Home Discount reconciliation rules for scheme years 16 to 20. The central change is structural rather than distributive: the back-end settlement between suppliers moves away from customer-number proxies and towards energy volumes, so the mechanism follows how suppliers actually recover Warm Home Discount costs in bills. This is the reconciliation counterpart to the wider 2026 Warm Home Discount redesign. DESNZ confirmed earlier this year that suppliers should recover scheme costs through gas and electricity unit rates from 1 April 2026, and the government has extended the scheme for a further five years to 31 March 2031. (gov.uk)
In practical terms, Ofgem will no longer use simple Great Britain domestic customer counts as the main basis for market share in reconciliation. Under the amendment regulations, suppliers must provide total volumes of electricity and gas supplied to GB domestic customers for reporting periods set by the Secretary of State, and the Authority must translate those data into a volumetric market share. That market share is not a raw units test. The formula is cost-weighted, using Warm Home Discount gas and electricity unit rates from Ofgem's Policy Cost Allowance Methodology and seasonal apportionment from the Wholesale Cost Allowance Methodology. DESNZ's stated aim is to match recovery more closely to actual consumption and the price-cap framework. (ofgem.gov.uk)
The drafting also gives ministers and the regulator more operating room. New regulation 4 lets the Secretary of State specify one or more reporting periods and reporting dates for each of scheme years 16 to 20, for interim reconciliation, final reconciliation or both. Ofgem must then issue the corresponding notice to relevant electricity and gas suppliers. If a supplier fails to report, the Authority is required to determine the figures as best it can from the information available. A new regulation 5A is equally important for compliance teams. It gives Ofgem a standalone power to request information or evidence for the reconciliation mechanism, outside the formal notice cycle from the Secretary of State. For suppliers, that means volumetric reporting, audit trails and group-structure records will need to be kept in order throughout the year, not only at year end.
The interim reconciliation formula has been rewritten so that projected liability now combines two elements: the value of standard rebate notices issued to a supplier, calculated at £150 per notice, and the supplier's original non-core spending obligation. That total is then compared with the supplier's latest volumetric market share of aggregate supplier commitments, producing either a payment from the Authority or a payment due to the Authority. That approach matters because interim reconciliation is now being used explicitly as a cash-flow management tool within the new unit-rate model. In its 2026 response, DESNZ said the earlier interim reconciliation used in 2025/26 had been helpful for suppliers with larger eligible customer bases and confirmed that an earlier interim stage would continue alongside annual volume-based settlement. (gov.uk)
For final reconciliation, the regulations move to an actual-liability model. Ofgem must total the real cost of rebates delivered in the scheme year and the supplier's original non-core spending obligation, compare that against the latest volumetric market share, and then net off any interim payments already made or received. The former estimate of undelivered rebates is removed altogether, which simplifies the year-end calculation and narrows the number of proxy inputs. The instrument also does the quieter but necessary housekeeping that often determines whether an SI works in practice. References are updated to the Warm Home Discount (England and Wales) Regulations 2026 and the Warm Home Discount (Scotland) Regulations 2026, Scotland's reconciliation continues through the same Part 2 architecture with modified cross-references, and scheme year 15 remains under the pre-existing 2022 reconciliation rules. Ofgem's current guidance already separates scheme year 15 from scheme years 16 to 20 and says dedicated reconciliation guidance for the new period will follow separately. (ofgem.gov.uk)
The operational effect for suppliers is more demanding than the explanatory note may suggest. Because electricity and gas volumes must be apportioned across quarters using Ofgem's published seasonal weightings, reconciliation will depend on the quality of consumption data, the accuracy of group-company mapping as at 31 December before the scheme year, and the treatment of connected electricity and gas suppliers within a corporate group. The rule change therefore sits as much with tariff, settlement and finance teams as with regulatory affairs. That is also where the risk sits. Suppliers told government that unit-rate recovery could create seasonal working-capital pressure, especially when rebate delivery is concentrated in autumn and winter but recovery through usage is lower in spring and summer. DESNZ accepted those concerns, but concluded that annual volume-based settlement plus an industry feedback loop and earlier interim reconciliation offered the best balance between accuracy, simplicity and deliverability. (ofgem.gov.uk)
For households, this instrument does not change the headline entitlement. The Warm Home Discount remains a £150 rebate, and the government's January 2026 response said the continued schemes across Great Britain were intended to support around 6 million low-income and vulnerable households in winter 2026/27. The policy change here is chiefly about how suppliers are rebalanced behind the scenes once those rebates and related obligations have been delivered. (gov.uk) Two drafting points deserve follow-up. First, the instrument states that no separate impact assessment has been produced, with analysis instead published alongside the 2026 scheme regulations. Secondly, the source text contains a date inconsistency: the cover information says the regulations come into force on 29 September 2026, while regulation 1(2) refers to 28 September 2026. That is the kind of detail suppliers and advisers will want to monitor for any correction slip or departmental clarification before the first reporting notices are issued.