The short answer
~1%
Green gas in the UK grid
Biomethane share of gas delivered through the national network, 2025-26
5.74p
Gas unit rate
Ofgem price cap, 1 April to 30 June 2026
29.09p
Standing charge
Daily fixed charge for gas under the April-June 2026 cap
£124.9m
Green Gas budget 2026/27
UK government funding for new biomethane plants (DESNZ)
Biomethane (refined biogas) is a genuine renewable fuel. It just exists in small volumes. To label a household gas tariff "100% green" today, a UK supplier almost always uses a small biomethane blend plus carbon offsets covering the rest. Only one UK supplier currently sells 100% biomethane retail gas.
The belief most UK customers hold (and why it costs them)
Most UK households on a "green gas" tariff assume the gas reaching their boiler is renewable. It feels reasonable. You pay extra for green, so green must be flowing through the meter.
In practice, that is almost never true. The UK gas grid runs about 99% natural gas, 1% biomethane. Your supplier cannot route biomethane to your house. Every home on the grid takes from the same mixed supply.
"Green gas" on a UK domestic tariff usually means one of three things:
Genuine biomethane
The supplier buys a volume of certified biomethane injected into the UK grid and matches it to your usage.
Small green blend
A small percentage (typically 5-15%) of biomethane in the supplier's overall mix. The rest is natural gas.
Carbon offsets
100% natural gas, with carbon credits bought from forestry or methane-capture projects elsewhere to "cancel out" the emissions.
Why most "green gas" articles get it wrong
Most consumer guides describe biomethane, congratulate the UK on its growth, and recommend "switching to a green gas tariff" without explaining that almost every retail tariff in that category is mostly natural gas plus offsets.
The article you want has to do three things at once:
- Explain how biomethane is made in plain language.
- Show the real volume of green gas in the grid, not the marketing share.
- Tell you which UK supplier actually delivers biomethane and which is selling you offsets in a leaf-shaped wrapper.
How green gas actually works
What green gas is
"Green gas" is the umbrella term for fuels made from biomass. The two that matter in the UK are:
Biogas
A mix of methane (50-65%) and carbon dioxide produced when bacteria break down organic waste in the absence of oxygen. Naturally occurs in landfill, marshes and compost. It can be burned on-site to make heat or electricity, but it is not pure enough to inject into the gas grid.
Biomethane
Biogas that has been cleaned and concentrated until it is 95%+ methane. It is chemically the same as natural gas. It can be injected straight into the existing gas network and burned in any household boiler without modification.
Biomethane is the one that ends up in homes. Biogas is used at industrial sites that have their own gas turbine.
Where UK biomethane comes from
In 2026 the UK has roughly 700+ anaerobic digestion (AD) plants. Of those, about 110 produce biomethane suitable for the gas grid. The rest produce biogas for local heat or electricity. Feedstocks include:
- Farm slurry and manure. About a third of UK biomethane comes from cattle and pig waste.
- Food waste. Council kerbside food waste collection feeds many of the larger plants.
- Energy crops. Maize, rye and grass grown specifically to feed an AD plant. Controversial because they compete with food crops.
- Sewage. Wastewater treatment works that turn their sludge into biomethane.
The Green Gas Support Scheme
The Green Gas Support Scheme (GGSS) is the government's tool for building more biomethane plants. It is funded by the Green Gas Levy, a small charge that gas suppliers have to pay and that turns up on every household gas bill. In 2026-27 the scheme has a budget cap of £124.9m and is open to applications until 31 March 2030.
In other words, every UK gas customer is already paying for green gas, whether they signed up to a green tariff or not. The cost is small (a few pounds a year on a typical bill) but it is universal.
Green gas truth checker
Drop in your gas use and your supplier's biomethane percentage. The calculator tells you what your annual cost looks like under the April-June 2026 price cap, how much of that is real biomethane, and how much is offsets.
How green is your gas bill really?
Live check against the April-June 2026 Ofgem price cap
Typical UK household uses about 11,500 kWh of gas a year (Ofgem benchmark).
Check the supplier's "fuel mix" page. Most UK "green" tariffs show 5-15%.
Your verdict
Genuine-green score
Based on Ofgem default tariff cap valid 1 April to 30 June 2026: 5.74p/kWh unit rate, 29.09p/day standing charge. Source: Ofgem.
Real-world impact on UK gas bills
On a typical 11,500 kWh annual gas tariff, the Ofgem cap puts the variable cost at about £660 a year, plus a standing charge of around £106. Total: about £766 a year for a typical household.
If your "green gas" tariff has a 10% biomethane share, that is £66 of genuinely renewable gas. The remaining £700 is natural gas. Any "100% green" or "carbon neutral" claim has to be doing offset work to cover that £700, and the quality of those offsets is rarely audited at the household level.
In short: pay a premium for "green" gas only if you have read the fuel mix and you are happy with what it really delivers.
Insider insight: the future of UK heating is not green gas
The hidden truth about green gas is that the UK government does not actually expect it to heat your home in 2050. The Climate Change Committee's pathway to net zero assumes most UK homes will move to heat pumps or hydrogen-ready systems, not biomethane.
Biomethane is being scaled up for sectors where electrification is hard: heavy industry, long-haul lorries, certain chemical processes. There is simply not enough cattle, food waste and sewage in the UK to heat 28 million homes through biomethane alone. The maths does not work.
That means a 2026 "green gas" tariff is really a transition product. It funds new biomethane plants that mostly serve industry. Useful, but not the long-term answer for your boiler. The long-term answer is electrification.
If you are deciding what to do with your heating budget in 2026, the order of impact is: insulation first, then heat pump, then green tariff. Paying a premium for green gas is fine, but it is the smallest lever you can pull.
How biomethane is actually made
Step 1
Feedstock collection
Farm slurry, food waste or energy crops are delivered to an anaerobic digestion plant. UK plants are typically located on farms or beside wastewater treatment works.
Step 2
Anaerobic digestion
Feedstock is sealed in oxygen-free tanks for 20-40 days at about 38°C. Bacteria break it down and release a mixed gas: about 60% methane, 40% CO2, plus traces of water and hydrogen sulphide.
Step 3
Upgrading
The biogas is scrubbed to remove CO2, water vapour and contaminants until the methane content is 95% or higher. The CO2 can be captured and sold to food and drink manufacturers (the same CO2 that puts bubbles in your soda).
Step 4
Grid injection
A small amount of propane is added so the calorific value matches natural gas. An odorant is added so leaks can be smelled. The biomethane is then injected into the local gas distribution network and flows straight to households like any other gas.
Step 5
Digestate
What is left in the digester is a nutrient-rich slurry called digestate, which farmers use as fertiliser. It replaces chemical fertiliser, which has its own carbon footprint, so the climate maths gets better.
Green gas, pros and cons
Advantages
- Biomethane is chemically identical to natural gas, so no boiler or pipe upgrade is needed.
- Captures methane that would have leaked from manure or landfill anyway.
- Produces a useful by-product (digestate) that replaces chemical fertiliser.
- Supports UK farmers and waste-handlers through the Green Gas Support Scheme.
Disadvantages
- Total UK supply is too small to heat all UK homes. Currently about 1% of grid gas.
- Most retail 'green gas' tariffs are mostly natural gas plus offsets.
- Energy crops compete with food crops if not managed.
- Burning biomethane still releases CO2 at the boiler, just from a renewable source.
What UK customers should actually do, in order
- 1 Insulate first. Loft insulation, cavity walls and draught-proofing cut your gas use directly. £200-£500 spend on a typical home pays back faster than any tariff change.
- 2 Look at heat pumps. The UK Boiler Upgrade Scheme covers up to £7,500 of the cost. A heat pump removes gas from your bill entirely. Best return for any homeowner planning a heating system upgrade.
- 3 Read the fuel mix before you switch to a green gas tariff. If the page does not give a biomethane percentage, assume zero. Genuine 100% biomethane is rare and worth knowing about.
- 4 Treat carbon offsets with care. Some are high-quality (verified UK methane capture). Others are paper. The label "carbon neutral" alone does not tell you which.
- 5 Compare against the price cap. Use the calculator above. If a "green gas" tariff is meaningfully above the cap, work out how much of the premium is genuine biomethane and how much is marketing.
Why this matters now
The UK gas grid will not decarbonise by adding more biomethane. The volume just is not there. What biomethane can do is plug genuinely hard-to-electrify sectors and support UK farms and waste-handlers. The Green Gas Support Scheme is the right tool for that, and the Green Gas Levy on your bill is already funding it whether or not you signed up for a green tariff.
Your single biggest household impact on gas emissions in 2026 is reducing the amount you burn (insulation), not changing the label on the molecule. The green tariff is a fine extra. It is not the lever.
Frequently asked questions
The Green Gas Levy is a small charge that licensed UK gas suppliers must pay to fund the Green Gas Support Scheme. The cost is passed on to customers as part of normal bills. It applies to all customers, not just those on green tariffs.
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