A green certificate is a tradable commodity proving that certain electricity is generated using renewable energy sources. Typically one certificate represents the generation of one Megawatt hour of electricity. What is defined as “renewable” varies from certificate trading scheme to trading scheme. Green certificates represent the environmental value of renewable energy generated. The certificates can be traded separately from the energy produced. Several countries use green certificates as a mean to make the support of green electricity generation closer to a market economy instead of more bureaucratic investment support and feed-in tariffs. The UK’s Renewable Obligation Certificate (ROC) is a notable example.