Question: When bmw activee is the vehicle type how many clean electric grid california (san francisco) measurements are there?
Schema: create table table_24620684_2 (clean_electric_grid_california__san_francisco_ varchar, vehicle varchar, PRIMARY KEY (clean_electric_grid_california__san_francisco_))
SQL: select count(clean_electric_grid_california__san_francisco_) from table_24620684_2 where vehicle = "bmw activee"