Because electricity produced from renewable energy sources is physically indistinguishable from electricity produced from conventional sources, the method of proof is crucial in ensuring that the public authority is getting value (including environmental value) for money.
Kuna taastuvatest energiaallikatest toodetud elektrienergia on tavalistest energiaallikatest toodetud elektrienergiast füüsiliselt eristamatu, on tõestusviis oluline kindlakstegemisel, et ametiasutus saab kulutustele vastava tulu (kaasa arvatud keskkonnatulu).