"Energy Efficiency is at the heart of energy affordability." Tony Earley, Chairman, CEO and President of PG&E Corporation

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How Occupancy Sensors Save on Energy Costs

By Jonathan Marshall

If I leave the lights on in my office — which of course I don’t — they stay on, drawing power, until someone on the custodial staff turns them off. Except for making my boss think I’m burning the midnight oil, that’s not a good use of energy.

With lighting representing nearly 40 percent of all electricity used in commercial buildings, and about a quarter of peak commercial loads, such waste can subtract measurably from the bottom line. That’s why upgrading lighting control systems, after installing more efficient lighting, is for many customers a logical next step in the search for bill savings.

Lighting represents 40 percent of energy use in commercial buildings.

Many Class A offices already use occupancy sensors to pull the plug when no one’s working. Smart owners know that state-of-the-art lighting and controls can increase the value of building space. They not only reduce energy bills, but can increase visual comfort, user choice, worker well-being and ultimately productivity.

As part of its award-winning energy efficiency program, PG&E recently partnered with EMCOR Energy Services to measure the installation cost and energy savings from advanced lighting systems and controls at the Contra Costa County Office of Education in Pleasant Hill.

The study analyzed three specific strategies to reduce lighting energy use through the control system. They included dimming lighting to appropriate levels, adding daylight sensors to raise or lower lighting depending on available sunlight, and installing occupancy sensors to dim or shut off lights when no one is present.

Learn more about the California model for energy efficiency

The hardware included new electronic dimming ballasts, a multifunction sensor and a wireless control system by Sunnyvale-based Enlighted, which has installed its controls in 6 million square feet of offices.

The biggest savings — 26 percent — came from simply adjusting overly bright lighting to the levels actually needed by workers in the office. But the addition of occupancy sensors also slashed energy consumption an impressive 22 percent. Daylighting controls had only a small impact because of the building design, but they can provide significant energy savings in other applications.

That’s the good news. The not-so-good news is that without incentives or rebates on the equipment, this retrofit would have a long pay back from the energy saved. Fortunately, PG&E has recently increased incentives for advanced lighting control systems like this, which will help to significantly reduce the payback period. Customers can learn more about these new incentives by contacting the Business Customer Service Center at 1-800-468-4743 or visiting the Customized Retrofit Incentives page.

“Projects like this look at cutting edge controls technologies,” explained Jeff Beresini, who led the study for PG&E. “Their costs are higher than more mature products but have been steadily decreasing over time.” Indeed, Enlighted claims that some of its customers enjoy a payback period of only two years.

Businesses can look forward to even greater energy savings as lighting and building controls are integrated through comprehensive energy management systems and as sensor technology improves.

A new report by the Department of Energy’s Pacific Northwest National Laboratory highlights the potential savings from using more sophisticated occupancy sensors — which accurately count the number of people in an area — to control HVAC systems. By adjusting fan speeds and local air movement depending on the number of people present, the average office building can save 18 percent of its total energy bill—much more than the savings from lighting alone.

“An 18-percent boost in building energy efficiency by modifying a single factor is very, very good,” said the lab’s team leader, Michael Brambley. “The savings were much greater than we expected.”

Email Jonathan Marshall at jonathan.marshall@pge.com.

This story originally appeared on pgecurrents.com.