UK GGSS extension: more time to deliver biomethane projects, a shorter tariff life for late starters
The Green Gas Support Scheme’s commissioning extension gives eligible biomethane projects until 31 March 2030 to complete construction, begin grid injection and submit their registration applications. The change took effect on 16 October 2026, with final Ofgem guidance published that day. It applies across England, Scotland and Wales.[1]
GGSS supports eligible biomethane produced through anaerobic digestion and injected into the gas grid. The extension separates the deadline for entering the application process from the deadline for completing a project.
The additional two years therefore provide a delivery window for qualifying applications, while retaining the existing entry cutoff and final payment boundary.[1]
DESNZ explicitly links the 2043 limit to avoiding an extension of costs beyond the existing lifetime of the Green Gas Levy, which funds GGSS. The policy accommodates slower project delivery while containing the duration of levy-funded commitments.[2]
The amendment does not move every existing project’s deadline. Different application cohorts retain different statutory limits.
Outer commissioning and registration deadline, by the date the stage-one tariff-guarantee application was properly made.
The amendment permits Ofgem to reissue tariff-guarantee notices for applications made on or after 10 December 2025, substituting a later date and, where necessary, changing or adding conditions.[3]
For applicants from before that eligibility date, DESNZ identifies withdrawal and reapplication as a possible route if the original commissioning date becomes unachievable. Re-entry remains subject to the prevailing eligibility conditions and available budget.[4]
The three-stage application structure remains important:[5]
The effective project deadline
The injection deadline stated in a tariff-guarantee notice already incorporates the available grace period. Applicants should not add another 182 days to it, and no grace period extends beyond the applicable final cutoff.[6]
For example, a project with an expected commissioning date in early 2027 could still lose its tariff guarantee during 2027 if it misses its individual deadline and has not secured an eligible revision. The national March 2030 date does not itself protect that project.
Existing applicants must request and substantiate a revised date
The authorised signatory must email GGSS.app@ofgem.gov.uk, providing the application reference and proposed new expected injection date. Ofgem checks the revised timetable against the application evidence, may request updated documents and, where a guarantee has already been granted, reissues the notice if it accepts the change.
Eligible applications in the budget queue can also request a revised date without losing their original application date or queue position. Once injection has begun, however, the expected commissioning date cannot be moved beyond the actual first-injection date.[7]
Choosing the latest possible date can postpone revenue
Ofgem’s guidance states that payments cannot begin before the approved expected commissioning date, including an amended date. Consequently, requesting March 2030 merely to maximise schedule protection could leave earlier production without GGSS payments if the plant finishes sooner.[6]
The statutory tariff start date is linked to registration: the date on which the stage-three application is considered properly made. First injection alone does not establish that date. An incomplete registration submission can therefore have a direct revenue consequence.[8]
Assumes commissioning, properly made registration and the approved expected commissioning date coincide.
These durations follow from the unchanged maximum term and fixed 2043 cutoff.[2]