How Lighting Improves Security
Lighting improves security in an obvious way: burglars and other intruders don't want to be seen. A light over each door in the house can deter burglars from the most obvious points of entry. A light on the driveway can provide security for those walking up to the house, giving would be attackers fewer places to hide.
One of the most common methods of security lighting is to use a motion detector. This has obvious advantages. If a light suddenly comes on, a would be intruder may conclude that someone is home and has switched on the lights. Even if he reasons that the lights are motion activated, he knows that the lights may have alerted the inhabitants of the house and drawn the attention of anyone along the street. Some motion sensitive lighting can even sound an alarm or light up a panel inside the house to make sure the residents are alerted to a potential intruder.
These hefty advantages make motion activated lighting the choice for many. However, there are disadvantages as well.
For people with dogs or other outdoor pets, motion activated lighting may be more hassle than its worth. If the pet roams free in the backyard, the lights will trigger on and off, on and off. Eventually, the homeowner will ignore the lights, saying "It's just that dog again." Sometimes it doesn't even take a dog. A squirrel can do the trick. Homeowners may get so used to the lights going on, seemingly at random, that they don't take the warning seriously. The lights may also not be much of a deterrent to a burglar working in the backyard or along the side of the house behind a fence. And if they're mounted too low, they can be easily disabled.
Beyond that, the lights are harshly bright and can be a nuisance to neighbors and passing motorists. The lights also require a fair amount of energy. So even though they don't stay on all the time, their periodic activation can add more than you might think to your energy bill.
An alternative is to use low energy lighting that is controlled by a darkness sensor. These lights stay on all the time rather than waiting for an intruder to breach the perimeter. That may have the effect of deterring the intruder in the first place rather than waiting for him to show up and possibly decide to go through with his plan despite the new obstacle.
Lower wattage lighting can also be placed throughout the yard rather than emanating from a single spot or two. This reduces the number of shadows for a burglar to find and hide in.
For most homeowners, a combination of the two will be the answer. You'll want motion activated lights to flood the most vulnerable points of your home. And low energy lighting can provide a nice, secure feel for the rest of it.