Question: Name the number for service dates for hoosier energy for petersburg
Schema: create table table_23958917_1 (in_service_dates varchar, owner_s___2009_ varchar, location varchar, PRIMARY KEY (in_service_dates))
SQL: select count(in_service_dates) from table_23958917_1 where owner_s___2009_ = "hoosier energy" and location = "petersburg"