Very often I hear of outrageous wattage claims on loudspeakers and I am left to a parable of my own creation:
Although a screwdriver stuck in a lamp socket will handle at least 1500 watts before the breaker trips, it won’t make much sound.
The term “wattage” in our field usually refers to speakers and amplifiers. In general higher numbers are a good thing. For an amplifier it is a combination measurement of how much voltage it can place across and how much current it can force through your loudspeakers. For a speaker it is an extrapolation of how much current it can pass before it literaly burns apart.
Music, particularly bass, is the power hog. Low frequencies mean longer duty cycles and simply higher electric bills. However, it is extremely important to have ample extra power (headroom) designed into systems even if they are solely designated for the spoken word. The human voice is full of momentary bursts and plosives, all of which consume logarithmically higher amounts of power for brief instants in time. The preservation of these transients is critical to articulate reproduction.
That being said we come to the bigger factor: efficiency. This is a measure of what a loudspeaker actually does with the power it receives. To sum up my earlier meditation, a speaker needs to be of quality manufacture, with lightweight yet rigid materials for it to be at all useful. A speaker that is rated only slightly (three decibels) more efficent than another will effectively reduce your electrical consumption by fifty percent.
Summing it up, a balance between power capacity and efficiency is key.