Guidance

Calculating the level of the Renewables Obligation for 2025 to 2026

Published 30 September 2024

The Renewables Obligation scheme places an annual obligation on UK electricity suppliers to present to Ofgem (the scheme’s administrator) a specified number of Renewables Obligation Certificates (ROCs) per megawatt hour of electricity supplied to their customers during each obligation period (which runs from 1 April to 31 March).

The Renewables Obligation Order 2015 (ROO 2015) requires the Secretary of State to publish the level of the obligation (in ROCs per megawatt hour) 6 months before the start of each obligation period, that is by 1 October.

This note sets out the level of the obligation for the 2025 to 2026 period and explains the underpinning methodology.

The total obligation

Setting the size of the total obligation requires 2 calculations:

• for calculation A (fixed target) we are required to estimate the total amount of electricity (MWh) expected to be supplied to customers during the 2025 to 2026 obligation period, for both Great Britain and Northern Ireland. The overall obligation (in ROCs) is then obtained by multiplying these figures by the fixed targets specified in the ROO 2015. These are 0.154 ROCs per MWh for Great Britain and 0.063 ROCs per MWh for Northern Ireland
• for calculation B (headroom), the expected number of ROCs to be issued in 2025 to 2026 is estimated and then uplifted by 10%

The total obligation, which is then used to determine the level of the obligation, is set as one of these calculations, determined as:

• fixed target: if the fixed target (Calculation A) is equal to or greater than headroom (Calculation B); or
• headroom: if headroom (Calculation B) is greater than the fixed target (Calculation A)

Calculation A sets the total UK obligation at 39.9 million ROCs by applying DESNZ’s projected trend in sales from the Energy and Emissions Projections to Ofgem’s outturn sales data for 2023 to 2024^{[footnote 1]}.

Calculation B sets it at 111.5 million ROCs, excluding headroom, and taking account of the cap on biomass conversion stations^{[footnote 2]}. Including 10% headroom gives a total of 122.6 million ROCs in the United Kingdom.

Calculation B is the higher of the two and must therefore be used.

The level of the obligation

The level of the obligation sets the number of ROCs that electricity suppliers are required to present to Ofgem per megawatt hour (MWh) of electricity that they supply during an obligation year.

Taking account of the current 100% exemption for Energy Intensive Industries in Great Britain from the indirect costs of the RO (see below), the number of ROCs that electricity suppliers are required to produce during the 2025 to 2026 obligation period will be:

• 0.493 ROCs per MWh in Great Britain (England, Wales and Scotland)
• 0.193 ROCs per MWh in Northern Ireland

Support for Energy Intensive Industries

Support for EIIs in Great Britain

An exemption for Energy Intensive Industries (EIIs) in Great Britain from up to 85% of the indirect costs of the Renewables Obligation was introduced for the 2018 to 2019 obligation year, and continued up to and including the 2023 to 2024 obligation year. The exemption was increased to up to 100% for the 2024 to 2025 obligation year onwards. The methodology set out in legislation for calculating the level of the obligation applies the ROCs/MWh rate to:

• 100% of electricity supplied to non-EIIs; and
• 0% of the electricity supplied to EIIs

The Department for Business and Trade (DBT)’s latest outturn figures for 85% exempt electricity supplied to eligible EIIs in 2023 to 2024 is 8.84TWh. The forecast for 2025 to 2026 (with 100% exempt electricity) is 10.69TWh.

Support for EIIs in Northern Ireland

An exemption from the indirect costs has not been introduced for EIIs in Northern Ireland. Instead, support is provided via direct compensation. As a result, the level of the obligation for Northern Ireland does not make any adjustments for electricity supplied to EIIs.

Caps on the ROCs received by certain biomass conversion stations

In 2018, annual caps were introduced on the number of ROCs that certain RO eligible biomass co-firing and conversion stations and units not protected by grandfathering^{[footnote 3]} can receive. There are 2 types of generating stations to which the cap mechanisms apply:

• capped generating stations, which comprise only non-grandfathered ‘capped’ units; and
• mixed generating stations, which comprise non-grandfathered ‘capped’ units and grandfathered ‘exempt’ units

At capped generating stations, there is a cap on the number of ROCs the station can be issued in each Obligation year. This is equal to 125,000 ROCs for each unit at the station. Stations can optimise generation across units, up to the level of their station cap.

For mixed generating stations, an overall station cap is calculated by first estimating the number of ROCs likely to be issued for generation at the exempt units during the Obligation year (the ‘exempt combustion unit estimate’). An allowance of 125,000 ROCs is then added for each of the station’s capped units. If generators choose to exceed their capped unit allowance, further ROCs will only be issued for generation at any of the station’s RO eligible units up to the level of the flexible station cap. If generators choose to stay within their allowance at their capped units, there will be no cap on the number of ROCs issued to their exempt units.

The following RO accredited generating station meets the definition of mixed generating station, based on Ofgem’s records:

• Drax Power Station, Selby, YO8 8PH

The station comprises 2 RO eligible exempt units (Unit #2 and Unit #3) and 1 RO eligible capped unit (Unit #4).

Overall station cap for Drax

The 2025 to 2026 exempt combustion unit estimate for Drax Unit #2 and Unit #3 will be set as follows, together with the capped unit allowance for Unit #4.

Type of unit	Unit number	No. of ROCs for 2025/26 obligation year
Drax RO eligible exempt (grandfathered) units	Unit #2	Estimate of number of ROCs likely to be issued in respect of relevant electricity generated during the 2025/26 obligation year	5,145,000
	Unit #3	Estimate of number of ROCs likely to be issued in respect of relevant electricity generated during the 2025/26 obligation year	5,145,000
Drax RO eligible capped (non-grandfathered) unit	Unit #4	Capped unit allowance for 2025/26 obligation year	125,000
Overall station cap			10,415,000

Further information on the calculation

Detailed information on calculation A and B is provided in the Annex to this notice.

Annex

Calculation A

Calculation A requires an estimate of the total amount of electricity (MWh) expected to be supplied to customers during the 2025 to 2026 obligation period, for both Great Britain and Northern Ireland.

To obtain the forecast of estimated electricity sales for the 2025 to 2026 RO calculation, we have applied DESNZ’s projected trend in sales from provisional Energy and Emissions Projections^{[footnote 4]} to Ofgem’s outturn sales data for 2023 to 2024, derived from their publication ‘Renewables Obligation: Total obligation for 2023 to 2024^{[footnote 5]}.

DESNZ’s provisional projections are made on the same basis as table 5.5 of the Digest of UK Energy Statistics (DUKES, published in July 2024)^{[footnote 6]}. Ofgem use their sales outturn data when they calculate the actual number of Renewables Obligation Certificates (ROCs) that each supplier must present to fulfil their obligation.

Ofgem’s published data on the total obligation for 2023 to 2024 sets figures of:

• 102,910,347 ROCs in England and Wales, and 10,268,199 ROCs in Scotland. That gives a total of 113,178,546 ROCs in Great Britain (GB)
• 1,329,926 ROCs in Northern Ireland (NI)

Dividing these total obligations by the relevant level of the obligation set by DESNZ for 2023 to 2024 (that is the number of ROCs that electricity suppliers are required to present to Ofgem per MWh of electricity that they supplied during an obligation year)^{[footnote 7]} gives the following outturns for sales in 2023 to 2024:

• 113,178,546 ROCs in GB ÷ 0.469 ROCs per MWh = 241.32TWh in GB in 2023 to 2024
• 1,329,926 ROCs in NI ÷ 0.184 ROCs per MWh = 7.23TWh in NI in 2023 to 2024

The Ofgem figure excluded exempt electricity supplied to eligible energy intensive industries in GB (there is no EII exemption in NI). The DBT outturn figure of 8.84 TWh for 85% exempt electricity in 2023 to 2024 is added to the GB and NI total of 248.55TWh to give a total electricity sales figure for GB & NI of 257.39TWh in 2023 to 2024.

EEP projections are produced in calendar years (CY) which are converted into financial years by taking three-quarters of the first CY plus one-quarter of the next CY. Applying the EEP trend to the 2023 to 2024 GB & NI sales figure increases the figure in 2025 to 2026 by 2.4%. That gives a forecast of 263.66TWh for GB & NI in 2025 to 2026 (here and below, the small differences in the totals compared to working it out from the figures given is because the percentage figures are shown rounded).

Based on the actual split of UK electricity sales across Great Britain and Northern Ireland^{[footnote 8]}, 97.2% of sales were in Great Britain, and 2.8% in Northern Ireland. Applying these to the 263.66TWh for the UK gives a figure of 256.37TWh for Great Britain and 7.30TWh for Northern Ireland in 2025 to 2026.

The overall obligation (in ROCs) for Calculation A is obtained by multiplying these electricity sales forecasts by the fixed targets specified in the Renewables Obligation Order 2015 to give the following:

• 256.37TWh x 0.154 ROCs per MWh for GB = 39.5 million ROCs
• 7.30TWh x 0.063 ROCs per MWh for NI =  0.5 million ROCs

This gives a UK total of 39.9 million ROCs for Calculation A.

Calculation B

Calculation B estimates the number of ROCs to be issued to stations expected to be operational during 2025 to 2026, for both existing and forthcoming stations.

For each installation, generation is estimated by multiplying the capacity by the number of hours in the year, and the expected load factor. The expected ROCs are then calculated by applying the banding level for that technology to the generation.

The list of existing sites was taken from Ofgem’s RO accredited stations database^{[footnote 9]}. Only those expected to generate in 2025 to 2026 have been included.

As the RO is now closed to all new applications, the only new additions will be stations that have already applied for accreditation but have not yet been processed by Ofgem. A list of these new stations was sourced from internal information from Ofgem. Only those predicted to generate in 2025 to 2026 have been included.

The details of the assumptions used in Calculation B are set out below^{[footnote 10]}.

DESNZ’s calculations give a total of 111.5 million ROCs before headroom. With 10% headroom added, the total is 122.6 million ROCs.

The calculation used for 2025 to 2026 (A or B)

Calculation B is higher than Calculation A. In accordance with the Renewables Obligation Order 2015, Calculation B must be used to set the level of the Obligation in 2025 to 2026.

Why Calculation B is much higher than calculation A

When the RO scheme was set up, there was little renewable electricity generation (at the end of 1999, it accounted for only 2.8% of total electricity generated in the UK). The aim of the scheme was to bring forward the additional generation needed to meet the UK’s then targets. So the scheme set out what were, at the time, ambitious targets for an annual increase in the percentage contribution of renewable electricity to total UK supply. It started as 3% in 2002 to 2003, rising to 15.4% in 2015 to 2016. It has not been upgraded since then, so calculation A is still based on that 15.4% target. 

Calculation B is based on expected generation under the RO, expressed in terms of ROCs to be issued, uplifted by 10% headroom. Current RO generation far exceeds the 15.4% target under calculation A - in 2022 to 2023, it accounted for nearly 32% of the UK’s total electricity supply.

Assumptions used for calculation B

Capacity of UK stations by technology

The following table sets out the breakdown of capacity (in GW) by technology for new and existing UK stations in 2025 to 2026 (the small difference in the total compared to adding up the figures is due to rounding).

Technology	Capacity (GW)
Biomass and waste technologies	3.6
Hydro, Tidal and Wave	0.7
Landfill gas and Sewage gas	0.9
Offshore wind	6.6
Onshore wind	12.5
Photovoltaics (Solar PV)	7.2
Total	31.7

Biomass and waste technologies include advanced conversion technologies, anaerobic digestion, dedicated biomass, biomass CHP, biomass conversions, co-firing of biomass, and energy from waste with CHP.

Load factors

Load factors are used to calculate generation from the capacity for each technology. The load factors presented below are net of availability, expressed on a total installed capacity (TIC) basis.

Load factor methodology

We have used monthly generation and capacity data (on an unchanged configuration basis) based on ROCs issued, as published by Ofgem^{[footnote 11]}.

Unchanged configuration load factors express average hourly quantity of electricity generated by stations operational the entire year (in the same configuration), as a percentage of capacity operational the entire year (from the same stations). As such, it removes bias from changes in capacity during the year (for example, because of sites beginning operation at the beginning or end of the year).

For biomass conversions and co-firers, given the small numbers of stations involved, we have used station-specific load factors based on actual generation data and discussions with industry experts.

Load factors for each technology

The two tables below set out the load factors for each technology and explain the data used to calculate the figures.

Onshore wind

The load factors for onshore wind are divided into territorial categories:

Category	Load factor	Source
England	26.1%	Based on a capacity weighted average of actual generation data from 1 April 2017 to 31 March 2024, on an unchanged configuration basis.
Wales	27.9%	Based on a capacity weighted average of actual generation data from 1 April 2017 to 31 March 2024, on an unchanged configuration basis.
Scotland	25.4%	Based on a capacity weighted average of actual generation data from 1 April 2017 to 31 March 2024, on an unchanged configuration basis.
Northern Ireland	25.2%	Based on a capacity weighted average of actual generation data from 1 April 2017 to 31 March 2024, on an unchanged configuration basis.

Other technologies

For all other technologies, the same load factor applies across the UK:

Technology	Load factor	Source
Advanced Conversion Technologies	41.1%	Based on a capacity weighted average of actual generation data from 1 April 2020 to 31 March 2024, on an unchanged configuration basis, pre-applying 50% Renewable Qualifying Multiplier.
Anaerobic Digestion	41.5%	Based on a capacity weighted average of actual generation data from 1 April 2019 to 31 March 2024, on an unchanged configuration basis.
Biomass CHP	67.1%	Based on a capacity weighted average of actual generation data from 1 April 2016 to 31 March 2024, on an unchanged configuration basis.
Dedicated Biomass	56.7%	Based on a capacity weighted average of actual generation data from 1 April 2019 to 31 March 2024, on an unchanged configuration basis.
Energy from Waste with CHP	34.8%	Based on a capacity weighted average of actual generation data from 1 April 2018 to 31 March 2024, on an unchanged configuration basis, pre-applying 50% Renewable Qualifying Multiplier.
Hydro	38.9%	Based on a capacity weighted average of actual generation data from 1 April 2013 to 31 March 2024, on an unchanged configuration basis.
Landfill Gas	31.6%	Based on the declining trend of generation from 1 April 2010 to 31 March 2024.
Offshore wind	41.4%	Based on actual generation with a wind speed factor correction.
Photovoltaics (Solar PV)	10.8%	Based on a capacity weighted average of actual generation data from 1 April 2017 to 31 March 2024, on an unchanged configuration basis.
Sewage Gas	46.5%	Based on a capacity weighted average of actual generation data from 1 April 2017 to 31 March 2024, on an unchanged configuration basis.
Tidal	13.2%	Based on a capacity weighted average of actual generation data from 1 April 2017 to 31 March 2024, on an unchanged configuration basis.
Wave	2.9%	Based on internal discussions on the stations in the RO, the historic assumption seemed reasonable.

Estimated number of UK Renewables Obligation Certificates (ROCs) to be issued by technology

The table below sets out the breakdown of the estimated number (in millions) of UK ROCs to be issued in 2025 to 2026 by technology. The total is the number of ROCs before the 10% headroom is added.

Technology	Total (millions of ROCs)
Biomass and waste technologies	22.6
Hydro, Tidal and Wave	2.6
Landfill gas and Sewage gas	2.7
Offshore wind	45.4
Onshore wind	28.1
Photovoltaics (Solar PV)	10.1
Total	111.5

1. See the Annex for an explanation of the sales data. ↩

2. See the section on Caps on the ROCs received by certain biomass conversion stations for an explanation of the cap. ↩

3. Grandfathering is a policy commitment that stations will receive no less support under the RO than they have received historically. Stations or units which generated at the biomass conversion band on or before 12 December 2014 are grandfathered. Stations or units which generated at the biomass conversion band after this date are not grandfathered. ↩

4. At the time the level setting calculation needed to be completed, the final Energy and Emissions Projections (EEP) for 2023 onwards were not available. So provisional figures have been used. The final EEP will be published in due course on DESNZ’s website at: ‘Energy and emissions projections’. These may differ slightly from the provisional figures used above, but the level of the obligation will not be altered. ↩

5. See Ofgem’s ‘Renewables Obligation: Total obligation for 2023 to 2024’. ↩

6. See the ‘Digest of UK Energy Statistics (DUKES)’. ↩

7. The level of the Obligation for 2023 to 2024 is available at: ‘Renewables obligation level calculations: 2023 to 2024’. ↩

8. Based on the average split since 2019, taken from Ofgem’s outturn sales, with EII outturn data from the Department for Business and Trade added for GB. ↩

9. Ofgem’s accredited stations database is available on the Ofgem Renewables and CHP Register. ↩

10. See the section Assumptions used for Calculation B. ↩

11. Ofgem’s certificate database is available on the Ofgem Renewables and CHP Register. ↩