An efficiently, well-lit house is ideal for security and entertaining. Dual purpose lighting and correct "on times" use less energy than traditional nighttime incandescent floodlights. Consider the purpose of your lighting to make the most energy efficient choices.
Less is more, even for floodlights.
Less lighting means more money in your pocket, both from fewer light fixtures to less electricity used. Two 150-watt floodlights will cost more than $100 per year, even when only turned on at night. Built-in or add-on motion sensors for floodlights will reduce the impact on your wallet.
Motion sensors only activate the light when something or someone moves within its range. Now, you are only using the light when you really need it. Motion sensors can reduce energy consumption by up to 90% for yards with very little traffic (wildlife or human). The life of the bulb can be extended by years, since the bulb will only burn on demand.
Higher end motion sensors have adjustable distance sensitivity. By setting the distance closer to the fixture, you can catch intruders in the beam as they near your house. Setting the distance farther from the house will deter animals from getting too close.
Watts, lumens, lux and dollars.
Each bulb will have a wattage, the number of watts required per hour to burn the bulb. This does not indicate how brightly the bulb burns. The higher the wattage, the more expensive it is to use the bulb.
Lumens are the measurement of light output or brightness. Lux is the actual light intensity and is measured in lumens per square meter. The higher the lumens, the brighter the light will be. The higher the lux, the larger the area the bulb will light.
Energy efficiency cannot be measured strictly in watts. The combination of the bulb and the light fixture will increase lux without using any additional energy.
Choose the correct bulb.
Wattage will determine which bulbs may be used with which fixtures. Shielded fixtures will have a maximum allowable wattage they can sustain.
Fluorescent bulbs are four times more energy efficient and last ten times longer than incandescent bulbs. Use fluorescent tubes and compact fluorescent light (CFL) bulbs. Full-spectrum CFL bulbs produce a whiter light than average fluorescent tubes and CFL bulbs.
Halogen bulbs produce a brilliant white light, which is good for entertaining and enhancing landscape appearance. While only 15% more efficient than incandescent bulbs, halogen bulbs are a substitute for CFLs in winter. Be certain to check the wattage of your fixture, as halogens burn very hotly.
Mercury vapor bulbs are another white light choice. While burning up to 50% less energy than incandescent bulbs, mercury vapor bulbs are not as energy efficient as their fluorescent cousins. Like flourescent bulbs, mercury vapor bulbs should be recycled at a mercury recycling center, since the mercury inside is released as a toxin into the air when they break.
Low pressure sodium (LPS) bulbs use only 15% of the enerfy burned by incandescent bulbs, but can be expensive to install. The bulbs take a short time to warm to full brightness and are a yellow light. Most common in parking lots and street lights, these outdoor lighting fixtures are the most energy efficient.
Solid-state lighting uses clusters of white light-emitting diodes (LED). Although not bulbs, the LED lights produce a bluish-white light which is extremely efficient. Burning as many as 100,000 hours, they last nearly forever. Most are grouped together when lighting for entertaining, as the individual fixtures have limited light output.
Aim it right.
Outdoor lighting should be aimed at the ground to increase efficiency and reduce light pollution. Choosing a light with a mirrored interior shield will intensify the light without increasing the amount of energy it uses. As you would aim a task lamp indoors, aim lights outdoors to areas you use to entertain or want to protect.
With ground mounted path lighting, increase efficiency by installing lower wattage bulbs, mirrored top shields and motion sensors so lights will have the least amount of on time.
Install shields on floodlights to aim them into areas where you entertain and reduce the amount of light escaping into the night sky. Remember, artificial light in the sky interferes with the navigation of nocturnal animals and your view of the stars.