Bests & Worsts Reviews from Amazon

I see some reviews saying this bulb does not work as specified - that it stays on even when the lamp is turned off. I suspect that has more to do with following the instructions than the bulb itself (although it's possible some folks got defective bulbs). Let me explain: The instructions tell you to leave the bulb on for 10 hours when you first get it. That’s not just to charge it – no battery this small takes 10 hours to charge. I suspect the bulb is figuring out the length of the wiring it is connected to – resistance, capacitance, whatever. When it figures that out it knows the difference between the lamp cord or light switch and a power failure. In my case, after charging it for 10 hours, when I turned the lamp off the bulb went out. I turned it back on and unplugged the lamp and it went out. But when I turned it back on and flipped the circuit breaker, it stayed on as that was farther away and simulated a power failure. So it worked for me and I suspect it will work for you. One minor thing that may apply to some people is that the portion of the bulb that lights up is closer to the top of the bulb than usual. If you look at my photos, the first shows a banker’s style desk lamp with a standard LED bulb in it. The second shows it with this bulb in it and you can see that the light is concentrated across half the lamp and not evenly disbursed. The third is in power failure mode, much dimmer and the same dispersion issue. If you are orienting the bulb vertically it won’t be an issue but I wanted to point this out. A handy bulb to have in a lamp somewhere in case you have a power failure. I liked the simplicity and the peace of mind.