Effective and economical expansion of renewable energy is one of the most urgent and important challenges of addressing climate change. However, many countries are facing a problem because the existing network was not originally built to accommodate renewables, which creates a mismatch between demand centers and renewable supply. Improving market integration enables renewable expansion in static and dynamic ways. Statically, market integration improves allocative efficiency by gains from trade. Dynamically, it incentivizes new entry of renewables. We show that an event study might capture static effects accurately, but it will tend to underestimate the benefits from transmission expansion if solar investments do not perfectly coincide with the event. We build a structural model of power plant entry and show how to correct for such bias. We apply our framework to a recent change of market integration in the Chilean electricity market—-two fully separated markets were integrated into one market in 2017. We find that market integration resulted in price convergence across regions, increases in renewable generation, and decreases in overall generation cost due to gains from trade. Furthermore, the dynamic impact quantified via the structural model indicates that a substantial amount of renewable entry would not have occurred in the absence of market integration. We show that ignoring this dynamic effect would significantly understate the benefits of the transmission line, including its impacts on allocative efficiency and renewable expansion.