A Guarantee of Origin (GO) is a certificate that proves one megawatt-hour of renewable electricity was generated somewhere in Europe. It exists for two reasons: it gives auditors and regulators a way to verify renewable claims that would otherwise be impossible to track on a shared grid, and it gives the wind farm or solar park that produced the electricity a second source of income alongside the wholesale price they receive for the power itself. The mechanism is sound. What varies, and varies enormously, is what any given GO actually pays for.
The same certificate scheme can fund a new offshore wind project or simply move paper between accounts of existing hydro plants that were built in 1960. Both transactions are legal. Both let a supplier label a tariff as "100% renewable". But only one of them changes what gets built next. Understanding the difference is the easiest way to tell a serious green tariff from a cosmetic one, and it is the reason informed buyers look past the headline label.
What GOs actually do
A Guarantee of Origin is an electronic certificate issued under the European Energy Certificate System (EECS), which covers EU members along with Norway, Switzerland, and Iceland. For every megawatt-hour of renewable electricity that enters the European grid, the generator receives one GO that records the source, the country, the technology, and the production month. Suppliers buy these certificates and retire them against the consumption they want to label as green. When you see "100% renewable electricity" on a bill in Europe, that claim is backed by retired GOs, not by a physical wire from a specific wind farm to your house.
The system has real value. It tracks renewable generation in a standardised way across borders. It lets corporate buyers make verifiable claims that auditors can check, which matters for Scope 2 reporting and for regulators. A renewable generator earns from two things at once: the electricity itself, sold into the wholesale market at the same price any generator gets, and the GO certificate, sold separately. Building renewables and running the certification process both cost money, and the GO revenue is the part of the income that pays specifically for the clean attribute of the power.
Market analysis from CE Delft confirms that GOs do add real revenue to qualifying renewable projects, on top of what those projects earn from selling the electricity itself. The mechanism works. What varies enormously, project by project, is how large that extra revenue is, and that depends entirely on the kind of GO being bought.
Where the variation comes from
GO prices in the European market range from under one euro per MWh to five euros or more, depending on the source, the issue year, and whether the certificate comes bundled with anything else. A 2023 unbundled GO from an old Norwegian hydro plant might trade for less than a euro. A recent-issue GO from a new German solar park, sold inside a structured contract, might trade for several times that. Both are valid certificates. Neither violates any rule.
The reason this matters is what researchers call additionality. The Ökoinstitut and others have spent years showing that cheap unbundled GOs from long-amortised plants send a very weak demand signal: those plants would generate anyway, and the GO revenue is a small bonus on top of decades-old economics. Premium GOs from new projects, or GOs bundled with a Power Purchase Agreement, send a strong signal because the buyer's commitment becomes part of the case for building the plant in the first place. The label "100% renewable" hides this difference. The price and the structure reveal it.
How PPAs strengthen the signal
A Power Purchase Agreement is a long-term contract, often ten to fifteen years, between a corporate buyer and a specific renewable project. It is frequently signed before the project is built, and the buyer's commitment to take the power at an agreed price is a key part of the financing case. Banks lend more readily, and at better rates, when revenue is locked in. Without a long-term contract committing a buyer to take the power at a known price, many new wind and solar projects would never get built, because banks are unwilling to lend against years of speculative wholesale price risk.
PPAs almost always come with the GOs from the same project, so the buyer receives the electricity and the certificates together as a coherent package. Reporting from BDEW in Germany has documented how this segment of the market has grown alongside corporate net-zero commitments, and energy disclosure rules at ADEME in France and Ofgem in the UK now require suppliers to spell out how much of their renewable claim is backed by PPAs versus unbundled certificates. The structure matters enough that regulators want it in the open.
The spectrum
The physical electricity is identical in every case, because it all comes from the same shared grid. What differs is what your purchase actually funds, and what you pay for it. The table below shows both.
The physical electricity in your socket is the same in every row. It is the national grid mix, which you can see in real time on dashboards like RTE eCO2mix in France or on disclosure pages run by VREG in Flanders and E-Control in Austria. The right-hand column is where the tariff actually does its work, and the price you pay is roughly proportional to how much of it lands on new capacity. Kiran's footprint estimates use this real grid mix data, not the green-label claim on your bill, because the physical electrons are what determine the actual carbon intensity of running your devices.
How to find a tariff that funds real new renewables
You do not need to be an energy analyst to ask better questions. Most national regulators publish supplier disclosures: Ofgem in the UK, BDEW members in Germany, VREG in Flanders, E-Control in Austria, and ADEME-aligned reporting in France. In the US, the EPA eGRID database and state-level REC tracking systems play a similar role, and AEMO publishes the underlying generation mix in Australia. Cross-country renewable shares from Ember Climate are a useful sanity check on whatever a supplier claims for their own portfolio.
When you talk to a provider, four questions are worth asking:
- Does the tariff include direct PPAs with named projects, and what share of your consumption do those PPAs cover?
- What is the issue year and country of origin of the GOs used for the remainder?
- Are any of the GOs from new-build projects, or are they all from existing plants?
- Does the provider publish a generation-source breakdown that can be checked against the national disclosure register?
A supplier that funds real new capacity will answer all four cleanly. A supplier whose green label rests on cheap unbundled certificates will tend to get vague around the second and third. If you want to see the difference your tariff makes in practice, Kiran's Insights page in the desktop app shows your device's footprint based on actual grid intensity for your country, with explanations of how the calculation works.
A note from our side
If you want the background on how the certificate system works in the first place, our companion piece on how green energy providers impact the grid covers the mechanics in more detail. When estimating the carbon footprint of your devices, Kiran's Agent feature uses real grid mix data, not certificate claims, so the numbers reflect the electricity that physically powered the work. GOs are still worth buying. They just deserve to be bought with intent.