This chapter analyzes patent trends in renewable energy technology from the 2000s to the 2020s across IP5 patent offices, with particular focus on wind and solar power. Global patent applications surged through the early 2010s, driven by coordinated policy interventions such as the U.S. American Recovery and Reinvestment Act, European feed-in tariff schemes, and China’s Five-Year Plan targets, before declining in most developed economies after 2012 due to policy reversals, falling fossil fuel prices, and solar technology maturation. Applying LMDI decomposition analysis, the chapter reveals starkly divergent national trajectories. In China, the SCALE effect was dominant in the 2000s–2010s, but the 2010s–2020s saw a strategic shift toward wind power, as evidenced by a strongly positive PRIORITY effect aligned with the country’s “dual carbon targets.” In the United States and Europe, the primary driver of decline was a strongly negative RENEWABLE effect—indicating diminished priority of renewable energy within environmental technologies—rather than overall patent contraction. Japan’s uniquely persistent negative SCALE effect, reflecting prolonged economic stagnation, was partially offset by post-Fukushima policy-induced solar growth before reversing sharply in the 2010s–2020s. South Korea maintained positive SCALE effects throughout, but mirrored Japan’s negative RENEWABLE trends. Collectively, the findings demonstrate that patent composition, not merely volume, reveals how each country’s innovation system responds to policy signals, market dynamics, and technological maturity.