Deal of the Week: The Power Failure Light 50% Off! Now $20. This device attaches between the socket and bulb of a standard table or floor lamp and provides reliable adjustable light during power outages. As soon as power is lost, the device automatically activates your preferred number of six LEDs–two LEDs provide up to 16 hours of uninterrupted light and all six LEDs provide up to eight hours. Powered by built-in rechargeable batteries that automatically recharge via the lamp socket once power is restored, the device has an integrated photocell that detects ambient light and prevents the LEDs from turning on during the daytime or when power is restored. Compatible with incandescent and compact fluorescent bulbs. 2″ H x 5″ diameter. (3 1/2 lbs.).