Lighting control strategies to save money
Editor’s note: This is the first of a two-part series on ways to cut lighting expenses in facilities. Part 2 of this series covers retrofit and renovation strategies that can help reduce lighting expenses.
Government facility managers can significantly reduce lighting expenses through flexible, scalable retrofits with a payback time frame of a few years.
Depending on the investment, facility managers can expect to shave 20 to 60 percent from lighting costs. Additionally, lowering lighting costs translates directly to lower HVAC costs. With less heat from the lights, there is less need for air conditioning. The rule of thumb is that for every three watts of lighting cut, a facility manager can reduce HVAC needs by one watt.
Lighting control systems employ a variety of strategies to save electricity use. The strategies and the resulting cost savings compound as each strategy is added to the overall lighting control system. That allows facility managers to build a total lighting control system gradually by employing one strategy at a time to suit any space and any budget.
Dimming is the easiest way to cut lighting costs. Dimmers can easily reduce electricity use from 15 to 20 percent through high-end trim, light-level tuning and personal light control.
High-end trimming sets the maximum light level for each space. For example, the human eye can barely distinguish between a light level of 100 percent and a light level of 80 percent. Dimming lights to 80 percent reduces energy use by about 20 percent while keeping light levels comfortable for the human eye.
Light-level tuning sets the appropriate light level for each space. Typical lighting levels in office spaces are much higher than necessary, which is often because of large, outdated banks of overhead lights that were installed before the widespread adoption of computers. Using high-end trim in addition to dimming lights in office spaces, for example, minimizes glare from computer screens and creates a more comfortable lighting environment for the human eye. Even when high-end trim is used, many offices choose to dim the lights even further to minimize glare on computer screens.
Personal light control gives individuals remote-control units to control the lights in certain areas of the office. Studies show that giving people direct control over their own lights can reduce electricity use by at least 10 percent.
Occupancy/vacancy sensing automatically turns off lights after occupants leave a room or space. On average, occupancy/vacancy sensors can reduce lighting electricity use by 15 percent. Depending on the use and size of a space, sensors can save electricity use by as much as 60 percent.
Daylight harvesting automatically dims electric lights when enough daylight is present. Daylight harvesting can save an additional 15 percent in lighting electricity costs in buildings with many windows or skylights. To ensure maximum savings, daylight harvesting lighting controls should be used with continuous dimming ballasts so the light can be gradually and continuously adjusted to maintain the internal lighting level as the availability of daylight externally changes. With continuous dimming ballasts, daylight sensors start to dim the lights as soon as daylight is sensed in the space, thereby immediately saving energy.
Controllable window shades serve a dual purpose to let daylight in and keep excess heat and cold out. For total control of the visual environment, shades can open and close automatically at different times of the day to harvest daylight and reduce HVAC costs by as much as 30 percent.
Demand response/load shedding reduces the overall lighting load at times when electricity costs are the highest. Many utility companies offer incentives to customers who are willing to reduce their electricity use during peak demand periods, i.e., during normal office hours when residents are at work, overnight hours or holiday hours. Lighting control systems are uniquely better suited to load shedding than other energy-saving technologies because they can respond quickly to changing conditions and operate safely at a wide range of power levels.
Scheduling will automatically dim or turn lights off at certain times of the day. Although some large facilities with many occupants operate on 24-hour schedules, most of the common areas are thinly populated during normal office hours, overnight hours and holiday hours. With scheduling, a facility manager does not have to depend on the last person that leaves a common area of the building to turn off the lights. The facility manager can use scheduling to automatically dim or turn off lights at appropriate times. Scheduling can reduce lighting costs by an additional 10 percent.
Andy Wakefield is Government Business Development Director, Lutron Electronics, Coopersburg, Pa.