A monthly exit fee that customers of alternative energy providers like Marin Clean Energy pay Pacific Gas and Electric Company to recoup money lost from historical contracts will double in the new year, following a 4-1 vote by the California Public Utilities Commission last Thursday. The price hike is projected to make it more expensive to purchase energy from M.C.E. than from PG&E for the first time in the alternative-energy program’s five-year history. Critics of…