WordNet (r) 3.0 (2006):

powerhouse
    n 1: a highly energetic and indefatigable person [syn:
         powerhouse, human dynamo, ball of fire, fireball]
    2: a team considered to be the best of its class
    3: an electrical generating station [syn: power station,
       power plant, powerhouse]

Moby Thesaurus II by Grady Ward, 1.0:

54 Moby Thesaurus words for "powerhouse":
   Antaeus, Atlas, Briareus, Brobdingnagian, Charles Atlas, Cyclops,
   Goliath, Hercules, Polyphemus, Samson, Superman, Tarzan, Titan,
   activist, atomic power plant, ball of fire, beaver,
   big-time operator, bully, bullyboy, bustler, busy bee,
   central station, colossus, doer, eager beaver, enthusiast, giant,
   go-getter, gorilla, human dynamo, hustler, hydroelectric plant,
   live wire, man of action, man of deeds, militant, muscle man,
   new broom, operator, political activist, power plant,
   power station, stalwart, strong man, strong-arm man,
   take-charge guy, the mighty, the strong, tough, tough guy,
   tower of strength, wheeler-dealer, winner