Energy-intensive firms can receive up to an 80% discount if they join a Climate Change Agreement (CCA), which requires meeting energy efficiency or carbon-saving targets. Renewable electricity suppliers are exempt from the CCL. Receipts from the CCL amounted to £0.7 billion in 2009. The RO requires electricity end-suppliers to purchase a certain fraction of their annual electricity supply from producers using specific renewable technologies, and they receive tradable Renewables Obligation Certificates (ROCs) for doing so. The supplier can also ‘buy out’ the obligation by paying a set price per MWh. The buy-out revenue is recycled to participating suppliers in proportion to their ROCs.