Measuring sustainability requires clear, reliable data. But once renewable energy enters the electricity or gas grid, it cannot always be physically distinguished from energy generated from other sources. This is why a system is needed to certify where it comes from.
Because of the way the electricity grid works, power from a specific source—such as a solar farm in Almería—cannot be sent directly to a particular outlet. As the Association of Renewable Energy Companies (APPA) explains in its industry reports, the grid functions as “one large, shared flow.” Once electricity from a solar or wind farm enters this vast energy highway, it becomes indistinguishable from power generated at other facilities, including those that use fossil fuels.
To solve this problem, the European Union developed the Guarantee of Origin (GO) system. A GO is essentially an electronic certificate that acts as an official passport for energy. It gives consumers reliable proof that the energy they use comes from renewable sources, mainly wind and solar power, as well as other technologies.
The next challenge is to match energy consumption with renewable generation hour by hour, using blockchain and other technologies already used in digital banking. Blockchain acts as a tamper-proof ledger, automating processes while making them faster and more secure.
The RED Directive
The current legal framework for this system is set out in Directive (EU) 2018/2001 of the European Parliament and of the Council, known as RED II, which was later amended by RED III. This EU legislation defines GOs as electronic documents that show consumers that a specific share of energy comes from renewable sources.
The European Union has defined these certificates as standardized instruments, each representing 1 MWh of energy and valid for 12 months from the date of issue. This helps maintain a steady flow of renewable generation to meet market demand.
For electricity, cross-border trade in renewable energy is supported by the Association of Issuing Bodies (AIB), the international organization that manages the European Energy Certificate System (EECS). This standard aligns the criteria for issuing GOs across more than 30 countries.
The Spanish context
In Spain, the system is closely overseen by the government. The National Commission on Markets and Competition (CNMC) is responsible for managing the Guarantee of Origin System, originally regulated by Ministry of Industry Order ITC/1522/2007 of May 24.
How does the system work across mainland Spain and its islands? Each year, the CNMC carries out an electricity “labeling” process, matching the guarantees issued to power plants with those submitted by energy suppliers on behalf of their customers. Although the GO system has expanded in recent years beyond electricity to include renewable gases, the CNMC, as the public regulator, focuses on recording and labeling the electricity supplied. This ensures that the same MWh (megawatt-hour) of renewable energy cannot be claimed by two different consumers.
Ultimately, the GO system is more than just a passive auditing tool. It also helps drive the energy transition. As explained in the Energy Union governance framework and by the CNMC, revenue from the sale of GOs goes back to renewable energy producers. Although it represents only a small fraction of the price per MWh, it provides an additional source of income alongside the revenue earned from the electricity generated.
This gives private investment in decarbonization an additional boost by helping make new solar and wind projects more financially viable and supporting the shift toward a more sustainable economy. Renewable Energy Guarantees of Origin have therefore become an essential tool for making the source of energy visible and traceable, bringing greater transparency to the market and making it easier to verify the use of energy from renewable sources.
