Occupancy sensors reduce energy case
TRW’s Space and Defense Park is an office building campus
of more than three million square feet in Redondo Beach, Calif.
Jerry Andis, the director of the company’s energy management
program when the lighting upgrade program began, knew that there
were opportunities to reduce the multimillion dollar lighting
energy bill. “We wanted a system that would be flexible
to meet our changing needs, that would be reliable in turning
the lights on and off, and that would be convenient for our employees,”
he said. Those criteria led Andis to occupancy sensors.
TRW conducted a painstaking, 18-month evaluation of options.
The first step was a pilot study in which different types of sensors
were installed in six offices. The energy savings shown in those
offices led TRW to install 550 sensors in two buildings. That
test confirmed the forecasts by the company’s energy management
team for cost and energy savings. As a result, TRW has retrofitted
more than 8,000 offices, labs, conference rooms and work areas
with occupancy sensors and continues to install the sensors in
The sensors have reduced by 50 percent the total number of kilowatt
hours used by TRW to light the offices where they are installed,
Andis says. The bottom line: TRW is saving more than $1.3 million
per year after the installation of the lighting controls. Each
sensor saves about $169 per year. Andis reports that the sensors
paid for themselves in 1.1 years, a 61 percent return on investment.
Lighting energy savings aren’t the only economic benefit
of lighting controls. By reducing the amount of time lights burn,
controls also reduce the cooling load of a building. And a reduced
cooling load can translate into smaller HVAC equipment in new
construction or renovation projects. Having the mechanical engineer
rightsize the HVAC system in this way can trim both first costs
and operating costs — savings the facility executives should
consider in the economic evaluation of lighting controls.