The article explores how hydrogen energy storage can help California shift to 100% renewable electricity. By using Power-to-Gas technology, excess renewable energy can be stored as hydrogen and later converted back to electricity when needed. The study shows that a combination of solar, wind, and hydrogen systems is needed for a successful transition. Massive increases in generation and storage installations are required, with a mix of technologies being more efficient than relying solely on wind or solar. This approach allows for flexible and long-term storage solutions to support a sustainable power grid.