CAISO curtailed 3.4 million MWh of solar and wind in 2024 because the grid cannot move clean energy from where it is generated to where it is needed

In 2024, California's grid operator (CAISO) threw away 3.4 million MWh of utility-scale renewable energy -- a 29% increase over 2023 -- because transmission lines between Southern California (where solar farms are concentrated) and Northern California (where demand is higher) are congested. Solar accounted for 93% of all curtailed energy. Why it matters: 3.4 million MWh is enough electricity to power roughly 500,000 California homes for a year, so ratepayers are paying for solar capacity that produces energy no one can use. Wasted generation erodes the economics of solar projects, so developers and investors see lower returns and become more cautious about building new projects in constrained areas. Fewer new projects in constrained areas means California must rely more on natural gas peaker plants during evening hours, so grid emissions remain higher than they need to be. Higher emissions undermine the state's climate goals, so California risks missing its 2030 and 2045 clean energy mandates. Missing mandates triggers more aggressive and expensive regulatory interventions later, so ratepayers face even steeper costs in the future. The structural root cause is that California built solar generation capacity far faster than it built the north-south transmission capacity to deliver that energy. Building a solar farm takes 1-2 years; permitting and building a major transmission line takes 10-15 years. This timing mismatch means generation consistently outpaces delivery infrastructure.