<p>This study investigates the impact of renewable energy forecast inaccuracies on system marginal price dynamics in Türkiye’s electricity market using daily time-series data. As the penetration of variable renewable energy increases, deviations between forecasted and realized generation introduce uncertainty into system operation and price formation. The analysis examines how market clearing prices, demand conditions, renewable energy forecast deviations, and system imbalance dynamics jointly affect system marginal prices. Methodologically, the study employs a semi-logarithmic time-series regression framework in which the system marginal price is expressed in natural logarithms, allowing estimated coefficients to be interpreted as percentage changes. Explanatory variables are defined as relative deviations between realized and forecasted values, providing an economically meaningful representation of forecast inaccuracies. To ensure reliable statistical inference given the time-series nature of daily data, the baseline specifications are estimated using heteroskedasticity and autocorrelation-consistent standard errors following the Newey–West procedure. The empirical results indicate that market clearing prices, demand deviations, and renewable energy forecast inaccuracies have statistically significant effects on system marginal prices, while system imbalance dynamics play a complementary role. Overall, the findings underscore the importance of improving renewable energy forecasting accuracy and enhancing system flexibility to mitigate price volatility and strengthen market efficiency in electricity markets with high shares of variable renewable energy.</p>