The system is administered by the official regulator Ofgem, and uses money from a levy on all electricity sales, collected and distributed by the licensed electricity suppliers as described here. Therefore if you install a renewable energy system you get a treble benefit:

• Your income from the Feed-in Tariff
• An extra income for every kWh you export
• Because you are producing some of your own power, you will buy less electricity and therefore pay less for it (and so less levy)