Outdoor solar lights are easy to install and virtually maintenance free. Best of all, using them won't increase your electric bill. Popular home uses for outdoor solar lighting include pathway light sets, wall-mounted lamps, freestanding lamp posts, and security lights.\nOutdoor solar lighting systems use solar cells, which convert sunlight into electricity. The electricity is stored in batteries for use at night. Manufacturers most commonly use nickel cadmium, sealed lead acid, and lead acid batteries.\nOutdoor solar lighting systems work well in most areas of the United States. However, it is important to consider geographic and site-specific variables when choosing a product. A solar lighting system will work well only as long as the solar cells receive the manufacturer's recommended hours of sunlight.\nThe "nightly run time" listings on most outdoor solar lighting systems are based on specific sunlight conditions. Outdoor solar lights located in places that receive less sunlight than the solar cells need will operate for fewer hours per night than expected. Nightly run times may also vary depending on how clear the sky is on any given day. Operating times in the winter months may vary as much as 30%–50% unless the solar lighting system has been sized specifically for winter operation. If the solar cells are shaded by landscape features (such as trees and buildings), battery charging and performance will also be affected. Watch for bird droppings, too. Insufficient battery charging will not only affect performance, it also may reduce the life of the battery.\nSome solar lighting systems are self-contained units: You only need to place the lights in a sunny location. Others have the lights separate from a solar cell panel, in which case only the panel needs to be placed in a sunny location. Units vary in size from small, glowing pathway markers to pole-mounted patio and high-beam security lights.\nBefore you buy an outdoor solar lighting system, check with the manufacturer to see if replacement bulbs or batteries are available. Some units do not provide replacement options.