Quota systems favor large, vertically integrated generators and multinational electric utilities, if only because certificates are generally denominated in units of one megawatt-hour. They are also more difficult to design and implement than a Feed-in tariff.Lauber, V. (2004). "REFIT and RPS: Options for a harmonized Community framework", ''Energy Policy'', Vol. 32, Issue 12, pp. 1405–1414.Lauber, V. (2008). "Certificate Trading – Part of the Solution or Part of the Problem?"