Utilities are obliged to purchase renewable energy electricity from different sources according to pre-defined ratios in order to foster more cost-efficient renewable energy technologies. Experience in Poland and Sweden shows that the legislator needs to set a sufficiently high penalty payment to enforce compliance with the quota obligation. The penalty should exceed the marginal generation costs for renewable electricity. Quota-based mechanisms sometimes operate without certificate trading and can also be combined with tender mechanisms or feed-in tariffs (FiT).