The feed-in tariff is a key support mechanism for renewable energy, guaranteeing plant operators a fixed payment for every kilowatt-hour fed into the public grid. In Germany, this is regulated by the Renewable Energy Sources Act (EEG), which secures the rate for 20 years plus the year of commissioning. The tariff decreases for newly installed systems through a degression mechanism, incentivising early adoption. Operators can choose between full feed-in, where all generated power is exported, or partial feed-in, where self-consumption is prioritised. Registration in the core energy market data register (Marktstammdatenregister) is mandatory. The system has driven widespread adoption of rooftop solar across residential and commercial sectors.