An energy certificate is a transferable certificate, record or guarantee, in any form (including electronic) in relation to the amount of a specific type of energy or material goods consumed by an energy conversion device in the production of a quantity of energy or material goods and/or the attributes of the method and quality of its production.
Energy certificates for renewable energy are also referred to as:
- Tradable Renewable Energy Certificates (TRECs)
- Tradable Renewable Certificates (TRCs)
- Renewable Energy Certificates (RECs)
- Guarantee of origin (GO)
- Green tags
- Renewable Energy Credits.
Energy certificates issued under national legislation are normally used to provide evidence of compliance with an obligation on electricity producers, suppliers or consumers to use energy of a specific type or in order to qualify for financial support: qualifying plant are often high-quality cogenerators, or produce electricity from renewable sources. Examples of this within Europe are the Renewable Obligation Certificates (ROCs) issued under the Renewables Obligation, and Levy Exemption Certificates (LECs) issued under the Climate Change Levy - originally part of the Finance Act 2001 - within the UK; Certificati Verdi within Italy; Elcerts within Sweden; and also within the three regions (Brussels, Flanders and Wallonia) of Belgium. At the time of writing, almost all such support schemes are national in character only, the transfer of certificates to and from other countries not being the intention of the policymakers. A notable exception is the Climate Change Levy: LECs are issued by the UK regulator to electricity producers both in the UK and in a number of European countries and exported to the UK, where they are purchased as proof of production of renewable energy production.
The European Union has also created internationally-transferable "guarantees of origin" to provide proof to consumers of the source of their electricity, as required by Directive 2009/72/EC: these are used by electricity suppliers when calculating the proportions of energy sources (e.g. fossil, nuclear etc.) in their supplied energy; and by government in calculating the "residual mix" (i.e. the blend of different sources of electricity produced in a country, adjusted for imports and exports. Directive 2009/28/EC and Directive 2004/8/EC give life to (respectively) guarantees of origin for renewable energy and highly efficient cogeneration, for use within the European Union and those countries with which it is bound by treaty (currently the European Economic Area and Energy Community of South East Europe countries). The international transfer of guarantees of origin is facilitated by the Association of Issuing Bodies' European Energy Certificate System.
Support certificates are also used in the United States of America, Australia, Turkey and Japan. They are under consideration elsewhere, including Russia and South Africa.
 The Environmental Tracking Network of North America (ETNNA)
 RECS International (RECS)