Greenwashing in Energy Contracts: Guaranteeing REGO-Backed Tariffs 

A REGO-backed tariff is legitimate, but it doesn't mean renewable power physically reaches your premises or that your money pays for new wind or solar farms. To guarantee what you're paying for, write the REGO backing into your contract, get written evidence that certificates were redeemed against your supply, and describe the tariff accurately in anything you publish.

Scrutiny of green tariffs is growing. Cornwall Insight's Green Certificates Survey found that REGO prices fell by 70% in three months in 2025, and its lead research analyst, Dr Matthew Chadwick, said the market was seeing "confidence in the REGO system itself start to crack". At the same time, more businesses want to show progress: Ofgem's 2025 research found 41% of UK businesses say nothing is stopping them from decarbonising.

This guide explains what a REGO does and doesn't prove, why REGO-backed tariffs are accused of greenwashing, how to compare different kinds of green tariff, how to make sure your tariff is genuinely REGO-backed, and what your business can safely claim.

Key points

• One REGO is issued for every megawatt hour (MWh) of eligible renewable electricity. Suppliers use them to prove the renewable share of the electricity they supply.
• REGOs are matched to your usage over a year, not hour by hour, and they can be bought separately from the electricity itself.
• Cornwall Insight found average REGO prices fell from £2.56 in January 2025 to £0.77 in April 2025, after peaking at over £15 in 2023.
• A REGO-backed tariff is a legitimate renewable claim, but it is not proof that your supply is funding new renewable generation.
• Put the REGO backing in your contract, check the evidence after each disclosure period, and avoid claims that suggest renewable power is delivered directly to your site.

What is greenwashing in energy contracts?

Greenwashing is making a product, service or business sound more environmentally friendly than it really is. In energy contracts it usually happens in one of three ways: a tariff name or label that suggests more than the evidence shows, supplier marketing that implies renewable power comes straight from a wind farm, or a business repeating its tariff's claims to its own customers without checking what sits behind them.

That last point matters. The CMA's Green Claims Code explains how consumer law applies to environmental claims, and the CMA has published guidance on how responsibility for green claims runs through the supply chain. If your business says it runs on renewable electricity, you need to be able to back that up, not just your supplier.

How REGO-backed tariffs work

Ofgem's REGO scheme issues one certificate for every MWh of eligible renewable electricity produced by accredited generators in Great Britain and Northern Ireland. The main use of REGOs is Fuel Mix Disclosure, which requires licensed electricity suppliers to tell customers the mix of fuels used to generate the electricity they supply.

The process runs on a yearly cycle. For each disclosure period, which runs from 1 April to 31 March, Ofgem's Fuel Mix Disclosure guidance says suppliers must hold the REGOs they use as evidence by midday on 1 July, and must publish their fuel mix by 1 October. In other words, a "100% renewable" tariff is checked after the event, over a whole year.

REGOs can reach a supplier in two ways. They can be bundled, bought together with the electricity from a renewable generator, often under a power purchase agreement (PPA). Or they can be unbundled, bought separately from the electricity, which the supplier may buy on the wholesale market from any source. Both are legitimate ways to back a tariff. They differ in how directly your money supports renewable generators. If you want to understand where the rest of the supplier's power comes from, our guide to how the wholesale energy market works explains the basics.

What a REGO does and doesn't prove

Why REGO-backed tariffs are accused of greenwashing

The certificate can be separated from the power

With unbundled REGOs, a supplier can buy electricity from any source and buy enough certificates to match it. The tariff is then disclosed as renewable. That is allowed under the rules, but critics argue it pays for a label rather than for more renewable generation.

The certificates are cheap

According to Cornwall Insight's Green Certificates Survey, average REGO prices for the 2024–25 Fuel Mix Disclosure period fell from £2.56 in January 2025 to £0.77 in April 2025. That was a 70% drop in three months and the sixth consecutive quarterly fall. Cornwall Insight said prices had reached average highs of over £15 per certificate in 2023, and linked the fall to a surge in renewable supply and corporate buyers moving towards alternatives such as PPAs.

When a certificate costs less than £1 per MWh, buying enough to cover a business's usage adds very little cost for a supplier, and sends a weak signal to anyone thinking of building new renewable generation.

Matching is yearly, not hourly

Because REGOs are matched over a year, renewable output from a windy night can be counted against electricity used on a still winter afternoon. The government's 2021 call for evidence on carbon content in energy products asked whether this kind of annual, retrospective matching gets in the way of transparency.

Green claims move renewables around on paper

When suppliers redeem REGOs for green tariffs, those renewable units are removed from the pool of unclaimed electricity. The government's fuel mix disclosure data table for 2025 to 2026 shows the UK fuel mix was 48.0% renewable, but the residual fuel mix, the electricity left after green claims had been made, was just 10.8% renewable and 65.3% natural gas. Green tariffs don't change how much renewable electricity the grid produces. They change who can claim it.

Confidence in the system is falling

Cornwall Insight reported in June 2025 that the government held a call for evidence on REGOs in 2021 and published a summary of responses in 2023, but had yet to set out a clear path for reform. It also noted that a new workstream on greenwashing and consumer transparency was expected as part of the Review of Electricity Market Arrangements, and that at least one major supplier had stopped buying REGOs altogether.

Green tariff types compared

Not every green tariff is backed in the same way. This table shows the main options, from the least to the most direct link to renewable generation.

How to guarantee your tariff is genuinely REGO-backed

Step 1: Before you sign, ask for the tariff's own fuel mix

Suppliers publish a fuel mix for their whole business, but a green tariff should have its own. Ask for the fuel mix of the specific tariff you are buying, the percentage backed by REGOs, and how much of that comes from bundled supply or the supplier's own stations. Ask which technologies the REGOs come from, as some buyers prefer wind, solar and hydro to biomass or landfill gas.

Step 2: Write the REGO backing into your contract

A green label on a quote or website isn't a contractual promise. Ask for a clause that states the percentage of your electricity that will be matched with REGOs in each disclosure period, confirms the REGOs will be redeemed against your supply, and says when you'll receive evidence. For example:

The Supplier will hold and redeem Renewable Energy Guarantees of Origin equal to 100% of the electricity supplied to the Customer's MPANs in each Fuel Mix Disclosure period (1 April to 31 March). Within 30 days of publishing its fuel mix disclosure for each period, the Supplier will give the Customer written confirmation, including the technologies and generating stations the REGOs relate to.

Treat this as a starting point and agree the final wording with your supplier, and with your legal or sustainability adviser if the claim matters to your business.

Step 3: Check the evidence after each disclosure period

Suppliers publish their fuel mix by 1 October each year for the previous April to March. After that date, ask for written confirmation that REGOs covering your usage were redeemed, and check it against what your contract promised. Keep it with your sustainability records. Our guide to the evidence your supplier should give you covers the documents to keep for audits, tenders and supply chain questionnaires.

Step 4: Check the green element of your price

Ask how much of your unit rate covers the green element of the tariff. At current certificate prices, REGOs alone add very little, as the cost table below shows. If a green tariff costs noticeably more than a standard one, ask what the extra pays for, such as bundled supply from named generators.

Step 5: Review it at renewal

REGO prices, supplier sourcing and reporting rules all change. Repeat these checks each time you renew, so your next contract still supports the claims your business needs to make.

Questions to ask your supplier or broker

What your business can safely claim

If you tell customers about your green tariff, the wording matters. The ASA's advice on renewable energy claims says claims such as "100% renewable electricity" can be acceptable without further qualification, provided they can be substantiated and don't imply energy is supplied directly from renewable sources. The CAP Code also requires absolute environmental claims to be backed by a high level of evidence.

How much REGOs cost, and why it matters for your bill

REGO prices move, so this table uses three prices reported by Cornwall Insight to show what the certificates behind a 100% REGO-backed tariff would cost at different levels of annual usage.

What's changing for REGOs and green claims

The rules for green tariffs and carbon reporting are under review, so it's worth knowing what's settled and what isn't.

• The REGO scheme still operates as normal. Ofgem's 2026 guidance to suppliers sets out the same Fuel Mix Disclosure process, with REGOs held by 1 July 2026 for the April 2025 to March 2026 period.
• Carbon reporting standards may tighten. The GHG Protocol's October 2026 update says the 2015 Scope 2 Guidance still applies. It is now developing two market-based methods: one with hourly matching, deliverability and new-build requirements, and one that keeps today's rules until a date not yet set. A consolidated public consultation is planned for Q2 2027, with a joint GHG Protocol and ISO standard due in Q4 2028.
• UK reform is still pending. The government has consulted on transparency in green tariffs, but Cornwall Insight reported in June 2025 that no clear path for REGO reform had been set out.
• Enforcement of green claims is stronger. The CMA's direct enforcement powers have applied since 6 April 2025.

When you compare renewable business energy tariffs with us, you can see options from several suppliers in one place. Use the questions in this guide to check what sits behind each tariff before you choose. You can also see which renewable energy suppliers are on our panel.