Competition in the electricity market allows customers to choose between suppliers. As a consequence, customers may demand electricity from specified sources of energy. In Sweden, the Swedish Society for Nature Conservation (SSNC), operates a system of environmental labelling of electricity delivery contracts since 1996. Labelling is available for suppliers offering electricity from renewable sources of energy with some additional criteria. Companies may acquire a licence to use the label by showing ability to deliver such electricity and by agreeing to be audited. The system is private independent. It is operating on the bases of credibility earned by the SSNC during 90 years as an environmental organisation and 10 years as operator of environmental labelling of consumer products. The system is market oriented, compatible with WTO and EU market principles, and independent of governmental environmental restrictions, subsidy or quota systems. It is relying on voluntary agreements. The results are desirable if only a few by electricity under labelled contracts as well as if every customer do so. The market is growing. A majority of the suppliers have a license and may offer labelled contracts. In the year 2000, 7% of all electricity sold to final consumers was sold under labelled contracts.