Use Timers or Photocells Outdoors

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Affordability

Timers are generally affordable, and many are plug-in products, so you do not need an electrician to install them. Photocells are less expensive than astronomical timeclocks.

Cost savings

While cost savings will vary widely from business to business, it is estimated that a billion dollars worth of lighting energy is wasted each year by needless lighting in the night sky. Meanwhile, amateur astronomers and members of organizations such as the International Dark Sky Association will thank you for helping limit light pollution.

Environmental considerations

For many situations, where outdoor lighting is required for only part of the night, the combination of a photocell and timeclock is the most energy efficient choice. The photocell will automatically turn a light on when natural light levels are low while the timeclock will turn lights off at a preset time.

What you need to know

Timers

• Most modern timers are digital, easy to operate, affordable and can be programmed from 24 hours to 7 days and can follow a seasonal daylight schedule. You can program the timer to turn lights on and off at specific times. Look for timer mechanisms that have manual override and a good power disconnect.
• The best timers have astronomical dials and quartz drive carryovers. They compensate for seasonal changes and keep time for up to seven days in a power outage.
• Timers/timeclocks are most effective when used to control bank of lights instead of a single lamp.
• Some digital timers do not operate CFL lamps efficiently. Check with the vendor when buying timers for CFL products and ensure your CFLs are compatible with timers.

Photocells

• Photocells allow the outdoor lighting system to adjust to changing seasons. If exterior lighting is needed for only a portion of the night, a photocell can be used to turn lighting on and a timeclock to turn it off. Some photocells have delay mechanisms to prevent temporary cloud cover from turning the lights on.
• Use only sensitive photocells with high intensity discharge (HID) lamps (mercury vapour, metal halide or sodium vapour). These lights take a long time to warm up, so the photocells need to be activated early to ensure the lights are on when needed.
• Clean and maintain photocells regularly as dirt and physical damage will affect performance.
• Position photocells where they will not be affected by other, inconsistent light sources that may trigger them to turn off.

FAQ

Should I use a photo cell or a timer to ensure I do not waste energy with outdoor signage?
One solution is to use both. The photo cell will ensure that a sign is only illuminated when it is dark out. And with a timer to complement the photo cell, you can ensure that the sign is off in the middle of the night, say from 11 p.m. to 6 a.m.