Table schema:
CREATE TABLE table_23840623_4 (dirty_electric_grid_rocky_mountains__denver_ VARCHAR, epa_rated_combined_fuel_economy VARCHAR)

Question: How many dirty electric grid rocky mountains (denver) vehicles have an  epa rated combined fuel economy of 102 mpg-e (33kw-hrs/100mi)?
SQL: SELECT COUNT(dirty_electric_grid_rocky_mountains__denver_) FROM table_23840623_4 WHERE epa_rated_combined_fuel_economy = "102 mpg-e (33kW-hrs/100mi)"