Davis Mega-Light Utility Light 
Mega Light Utility
Mega-Light energy efficient lights consume very little current. At just 0.110 amps (approximately 1/10th amp), battery discharge is about one amp hour in a 12-hour period. Your batteries will hardly know it's on.
Mega-Light Utility features a light sensor that automatically switches on at dusk and off at dawn. It sports a dual-function Fresnel lens that projects light for up to two nautical miles (3.7 km).
Comes with two easy-to-change light bulbs. One bayonet-type bulb draws just 0.110 amps and can be seen for up to two nautical miles (3.7 km). The other bayonet bulb draws 0.320 amps (approximately 3/10th amps) and is more than twice as bright. Includes a standard lighter plug and 15 foot (4.5 m) cord with easy hanger.
Quick Guide (pdf)