How Much Energy Are You Wasting Overnight?

03/30/2017 | By Janelle Penny

Stop paying to light up the night and right-size your energy spend

Even if no one’s working late, your building may still be burning the midnight oil – literally. Overlit exteriors and lights that are left on could be driving up your lighting-related energy consumption overnight, when little to no illumination is needed.

“Light is wasted any time a person doesn’t need it, either because the space is unoccupied or because more electric lighting is being provided than is needed,” explains Jeremy Snyder, Director of Energy Programs at Rensselaer Polytechnic Institute’s Lighting Research Center. “There are many opportunities to reduce wasted light. Paying attention to these opportunities can result in cost savings.”

Discover where your building is wasting lighting and what to do about it with these tips.

Why is Light Wasted?

Building owners frequently don’t notice that there is a problem, either because lights are left on when no one is around to notice or because they don’t realize that some intentionally lighted spaces are overlit, says Todd Houghton, Vice President of Energy Efficiency at GenPro Energy Solutions, which designs and implements renewable energy systems and energy efficiency projects.

“People drive past their building, see that their parking lot is lit and that’s all they care about because it’s supposed to be lit,” Houghton adds. “Until you actually show them that it’s overlit and they can save money by lowering the energy consumption, they may not recognize that they have a problem because they’re focused on running their business.”

Organizations purposely leave lights on for three key reasons, notes Cynthia Gibson Murphy, Project Manager and Associate Partner at Margulies Perruzzi Architects:

  • Safety: “If a space is not equipped with occupancy sensors, then egress lighting may be programmed to stay on 24/7,” Murphy explains. “This can be as much as 25% of the light fixtures in open and circulation spaces inside a building, which can be a fairly substantial load.”
  • Security: Exterior lighting is often left on to discourage people from approaching, gathering or loitering, Murphy says.
  • Focal points and branding: “Highlighting building features is common,” Murphy says. “Often lights that simply highlight plantings will be on a timer, while others are on daylight sensors. They turn on and increase brightness toward dusk, but actually dim down to reduce glare, intensity and energy when it’s fully dark out and less light is actually needed.”

Interior lights are often left on inadvertently by occupants or cleaning staff, especially if they use manual lighting controls that are in an inconvenient location, adds Snyder. Automatic shut-off controls may not do their job if they haven’t been properly adjusted. Outside, broken photosensors may mean exterior lights stay on when they’re not supposed to, further driving up energy costs.

How to Find Waste

A good first step to identify wasted light is to conduct your own investigation, Snyder suggests. Walk around and observe your property yourself, both during the day and after hours when lights should be off. Alternatively, you can bring in a professional to conduct a comprehensive lighting audit, says Danny Streit, President of Lumen Control Solutions, an architectural lighting design firm.

“Most lighting audits begin because the owner is interested in the energy savings,” Streit explains. “Typically, someone comes on-site in the evening and looks at areas where energy could be saved either by turning lights off, reducing the light output or retrofitting to a more efficient source like LED. There are also metering devices you can install temporarily that measure usage patterns.”

Houghton recommends comparing the light levels in each space to the code for your city, county or state: “Look at the minimum of light you have to have, then walk around the parking lot, sidewalk and sides of the building with a footcandle meter to see if you’re within the codes in regards to minimum light. From there, look at doing other things, like adding controls.”

Identify Interior Issues

Older buildings tend to waste interior lighting energy along any emergency egress paths, especially in stairways and any other places that aren’t regularly used, Murphy notes. Hotels and other hospitality facilities also have to light hallways at all hours, adding additional waste. Lobbies and entryways are also typically lit nonstop.

“MPA has helped property managers add local occupancy sensors on stairwell lights that will turn on as people approach them,” Murphy says. “As these are egress paths and need to be well-lit for safety, it’s important to test out the location of the sensors to make sure they capture people within their view before they get to spaces that are not lit.”

Buildings with older sensor technology (or none at all) tend to waste a significant amount of energy on lighting, but even buildings with newer equipment are vulnerable if the sensors aren’t programmed correctly or occupants override them.


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