When the power goes out, the Ascella LED, $15, automatically comes on thanks to a built-in battery. So you don't have to stumble in the dark looking for a working flashlight. Simply remove the Ascella from the lamp (the bulb stays cool to the touch) and extend the base of the bulb so that it acts as a handle, and you're good to go.
But the Ascella isn't as bright as a typical LED flashlight, and its light fades over the three hours it stays illuminated. To have the light automatically come on when the power is out, you have to set the bulb's three-way switch to emergency mode, and the lamp it's in must be turned on. When the fixture is on, the bulb charges itself. Recharging the Ascella takes three to four hours.
When the Ascella is recharging after being used in emergency mode, it doesn't produce any light, so you can't use the lamp for general light. Nor would you want to. The Ascella casts a very dim, bluish light. Although it met its brightness claim of 150 lumens, that's less than half as bright as many 30-watt lightbulbs, which the Ascella is supposed to replace.
This LED's claimed life is about 18 years (based on usage of three hours a day), but here's a brighter idea: Know where your flashlights are and check the batteries periodically.
The Ascella LED may be a novelty, but in Consumer Reports' lightbulb tests we found many reliable replacement lightbulbs for both indoor and outdoor fixtures. Seven of our top-rated lightbulbs scored a 99 out of 100, and many more did nearly as well.