With the advent (decades ago) of cheap dawn-to-dusk mercury vapor yard lights, some homeowners went a
little bit overboard. While many believe yard lights increase protection from criminal types, others argue all-night lighting just highlights that no one is home (or calls attention to your shiny things). Alas, this argument could rage for millennia. In any case, all-night lighting has some definite drawbacks, and better technologies—including
efficient outdoor lighting options—are out there!
Studies are increasingly showing that all-night light (especially white) isn’t so great for wildlife—and if it shines into nearby houses, it can make your neighbors grumpy. As these lights proliferate, even suburban areas are losing their former views of stars in the night sky (read:
light pollution). Some communities are passing “dark sky ordinances” regulating the lighting that can be used.
Plus, outdoor lighting can needlessly guzzle energy and money—
which, with efficient outdoor lighting available, is just plain silly. If a mercury vapor yard light were on during just the dark hours, it would cost about $50 a year. Using a 23-watt
compact fluorescent light bulb instead would cost only about $11 a year. Though it may take two fixtures to provide the same amount of light, it’s still substantial savings. (Estimates use a utility rate of $0.11/kWh and assume an average of 4,380 hours per year.)
Instead of slathering light around your neighborhood like overambitious margarine, a lower light output can do the job if you use light fixtures to point the light where it’s needed. And you can add shields to existing fixtures to let your neighbors sleep. Here are some of your options for outdoor lighting:
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Mercury vapor. It’s the pits. Although it lasts a long time, it produces less light as it ages while using the same amount of energy. Since it isn’t “burned out,” owners may not replace it even though it’s doing no useful work. It should be replaced at about 10,000 hours (less than half the life of high pressure sodium lighting).
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High pressure sodium (HPS). These little buddies last a long time and provide double the light for the same wattage as mercury vapor. Their odd yellowish light can make it hard to identify your own car in a crowded parking lot because of the poor color rendition, but that shouldn’t be a problem at home unless you’re Tony Stark. For areas where white light is critical, consider a portable work light.
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Metal halide (MH). Metal halide is a white light option, best used for specific tasks rather than all-night lighting. It produces less light for the same wattage as HPS products and has a shorter lamp life.
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Compact fluorescent light bulbs (CFLs). CFLs also produce a white light, but are not as powerful as the other products in consumer lighting. However, in some applications lower mounting heights for CFLs will be all that is needed. In many cases more light at lower heights does a better job of lighting areas than a higher, central light source.
Switching to efficient outdoor lighting alone will save energy; integrating timers and/or motion sensors in addition to photo sensors can help you save even more. Motion sensors have the advantage of highlighting when someone is in the area, alerting occupants to another’s presence. None of the above technologies are suited for motion sensor operation since it takes them a while to get to full power (up to fifteen minutes), and some require a cool-down period before they can come back on. Here are a couple energy-efficient outdoor lighting options usable with motion sensors:
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Light-emitting diodes (LEDs). LEDs are finding a place in parking lots and street lights. While currently very spendy, the cost should come down and technology should improve. LEDs can be used with motion sensors and may have dimming capabilities as well. Since they’re directional lights, a good design will easily stop light, uh, leakage. Watch for products in coming years.
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Incandescent halogen lamps work well with motion sensors that are well-calibrated. While halogen lights produce a bright white light and aren’t efficient over time, they can be a good choice with short and infrequent operating times. If your location is such that they’re on more often than not, a more efficient technology running on a timer might be better.
While most current solar-powered outdoor lighting isn’t powerful enough for broad or intense area lighting, watch for new products in the future.
1. Consider where, when, and how long you need light. Most lights don’t need to be on all night. Pick a technology that works for your situation.
2. Make sure the light from your fixture doesn’t spill onto streets or adjoining property where it might interfere with drivers or neighbors. Choose a fixture that only lights necessary areas.