Clifford D. Simak 
Empire 

Who controls power controls the Solar System, and Interplanetary Power, through its power accumulators controls power. Spencer Chambers, the president of Interplanetary Power, used that control to rule the Solar System with an iron thumb that allowed no dissent. When Russell Page and friend Harry Wilson develop an alternative source of power they find themselves drawn into a conflict that will decide the fate of the system, and whether man will live in freedom or as slaves.