Engadget's new buying guide argues that wattage is one of the most visible Bluetooth speaker specs, but it is not a reliable way to predict loudness or quality. A 20-watt speaker is not twice as loud as a 10-watt model; doubling electrical power raises sound output by only about 3 dB, while a tenfold power increase is needed for a listener to perceive a doubling in loudness.
A bigger problem is that manufacturers often advertise peak power ratings, which can only be sustained in short bursts, instead of RMS ratings, which reflect continuous power handling. Retailers may not distinguish between the two, and some models have RMS figures listed only on the maker's spec sheet rather than at the point of sale.
The practical takeaway: buyers should look for RMS ratings and consider driver sensitivity and room size. Engadget suggests that sub-50W RMS speakers generally work for indoor use, while outdoor settings call for 40W to 100W or even higher-powered units like the JBL Boombox and PartyBox. Power ratings, the guide concludes, are a starting point rather than a definitive measure of performance.