CREATE TABLE table_23840623_4 (epa_rated_combined_fuel_economy VARCHAR(255), operating_mode VARCHAR(255), dirty_electric_grid_rocky_mountains__denver_ VARCHAR(255))
What is the epa rated combined fuel economy for the all-electric vehicle with dirty electric grid rocky mountains (denver) of 330 g/mi (205 g/km)?
    
SQL: SELECT epa_rated_combined_fuel_economy FROM table_23840623_4 WHERE operating_mode = "All-electric" AND dirty_electric_grid_rocky_mountains__denver_ = "330 g/mi (205 g/km)"