Phaser power
Phaser power was the source from which phaser energy was derived, inasmuch as it could be delivered at variable levels. 

The rerouting of "all but emergency maintenance power to the shields" on the original  starship, would reduce the ship's phaser power by fifty percent. ()

Later, in the redesigned Constitution-class refit, phaser power was increased" by channeling it through the main engines," so when if the ship experienced an antimatter imbalance, its phasers were automatically cut off. ()

Phaser power aboard the  was "almost doubled" by "running the plasma conduit through the primary phaser coupling". The process, which normally would affect a starship's warp drive efficiency, actually increased the Defiants by thirty percent. ()

See also 
 Disruptor power
Physics