I started getting curious about this. See, rating lights by how many watts is pretty popular these days and I was wondering exactly how much lie is included in those numbers. It looks like, for the most part, lights are within a plausible range, but I suspect that some of the lights on the market aren't actually running a full watt of power through the LED.
From the datasheets of Durcaell batteries, we can construct the following table using alkaline batteries:
|Power consumption||2 AA||4 AA||2 AAA||4 AAA|
After looking at the various lights advertising wattage figures on their LEDs, it's clear that there are both 1W lights that draw far more than 1W, thus are inefficient... and 1W lights that draw far less than 1W, thus making you wonder why they bothered with a 1W light. Like most things, you can move the parameters around, perhaps assuming the dim light from a nearly-dead alkaline is OK.
Blinking also plays a role. It's quite possible for a light to blink brighter than it can light up normally.
Also remember that watt is a matter of power capacity. One-watt LEDs started at around twenty lumens and are now several times that. This means that a company could offer a light that's twice as bright as their half-watt light but that uses only a little bit more power.