GGSS budget caps, production factors, and inflation forecasts for 2025-2026
Updated 20 December 2024
Applies to England, Scotland and Wales
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This page covers the Green Gas Support Scheme (GGSS) budget caps and their supporting information effective for the 2025-2026 financial year (1 April 2025 to 31 March 2026).
The Department for Energy Security and Net Zero (DESNZ) is required to publish this information under the Green Gas Support Scheme Regulations (reg. 4(13)).
The GGSS has 2 budget caps, which are shown in Table 1: the Application Budget (AB), which limits estimated spend by acting as a cap against which all applications to the scheme are checked, and the Overall Scheme Expenditure Budget (OSEB), which sits above the AB, and is used to set the Green Gas Levy rate.
This page also contains the production factors (Table 2) and inflation forecast (Table 3) used to set the budget caps for the 2025-2026 financial year, which are used in the assessment of applicants’ estimated annual payments against available budget when they apply for a tariff guarantee.
Further information on GGSS budget caps and the production factors and inflation forecasts used to set them is published on the GGSS Budget Management Guidance page.
Budget caps
Table 1: GGSS budget caps (set 20 December 2024, effective from 1 April 2025)
| Year | 2025/26 | 2026/27 | 2027/28 | 2028/29 | 2029/30 |
|---|---|---|---|---|---|
| AB (£M) | 80.3 | 124.9 | 174.2 | 203.8 | 214.3 |
| OSEB (£M) | 86.3 | 143.6 | 200.3 | 203.8 | 214.3 |
Production factors
Production factors are used to estimate the proportion of a plant’s total registered capacity that we expect to be used to produce eligible biomethane in any given quarter of a plant’s time on the scheme.
Table 2: Production factors used to estimate AB commitments from 1 April 2025
| Quarter following registration | Production factor |
|---|---|
| Q1 | 47% |
| Q2 | 60% |
| Q3 | 63% |
| Q4 | 68% |
| Q5 | 69% |
| Q6 | 71% |
| Q7 | 71% |
| Q8 | 74% |
| Q9 | 74% |
| Q10 | 76% |
| Q11 | 78% |
| Q12 | 79% |
| Q13 | 79% |
| Q14 | 78% |
| Q15 | 79% |
| Q16 | 80% |
| Q17 | 83% |
| Q18 | 83% |
| Q19 | 84% |
| Q20+ | 85% |
Inflation forecast
Ofgem is responsible for uprating GGSS tariffs annually on 1 April, using the actual CPI rate from the previous December. This covers inflation for that calendar year and is published by ONS each January. Forecasts from the Office for Budget Responsibility’s (OBR) Consumer Price Index (CPI) forecast are used to set budget caps. The OBR forecasts are used as they are available at the time of budget setting, and are the forecasts closest to the figure that Ofgem will use – the forecast rate for Q4 for each calendar year is the closest to the December rate.
Table 3: Inflation forecast used to estimate AB commitments from 1 April 2025
| Financial year | 2025/26 | 2026/27 | 2027/28 | 2028/29 | 2029/30 |
|---|---|---|---|---|---|
| Estimate of CPI inflation | 2.4% | 2.5% | 2.1% | 2.1% | 2.1% |