It offers a more nuanced view of FITs than is often offered. In turn, it extracts four key lessons lawmakers should keep in mind when designing FITs: (1) the laws tend to be effective, but (2) internal modification of the laws’ design is unavoidable, (3) feed-in tariffs often impact the legal and physical systems around them in unforeseen ways, and (4) FITs’ unpredictability must be carefully managed.