The days are getting shorter and many people are
considering adding outdoor lighting. If you need to illuminate outdoor areas,
such as large yards or farm operations, electricity can be a significant cost.
Energy-efficient lighting takes two approaches: using the most efficient types
of lamps (bulbs), and using efficient controls to determine when the lighting is
used.
The most common residential outdoor lighting uses
standard inefficient incandescent light bulbs. These cheap-but-inefficient lamps
waste about 90% of their electricity by making heat instead of light.
Metal halide lighting and high-pressure sodium
lights are a better option for outdoor lighting because they are 3 to 4 times as
efficient as incandescent lights. Metal halide is the best choice when you want
lighting that produces natural colors. If color doesn’t matter, choose
high-pressure sodium lamps. They produce a yellowish light, but they are one of
the most efficient types of lamp and they also last the longest.
Automatic controls can save 20 to 90 percent of
lighting costs depending on which type of control is used and if they are used
correctly. The most common type of automatic control is the motion sensor. If
you only need light for someone walking by or to discourage prowlers, choose
off-the-shelf incandescent light fixtures with built-in motion sensors. In this
case the inefficiency of occasionally using incandescent lighting isn’t as
important as minimizing the on-time of the light.
Both metal halide and high-pressure sodium lights
have ballasts that require a warm-up period and so aren’t compatible with
motion sensing controls that require the light to come on instantly. These
lights should be fitted with photocells or time clocks for efficient automatic
control.
Photocells turn lights on when it is dark
outside. They work well for controlling individual lights and are cheaper than
time clocks. Be sure to shield photocells from other nearby lighting sources
that could cause them to turn off during the night.
Time clocks are more expensive but are the best
solution for controlling large groups of lights. Be sure to choose one that
compensates for seasonal day-length and doesn’t need to be reset after short
power outages.