Advanced Lighting Control System Performance: A Field Evaluation of Five Systems

A recent field evaluation report documents findings including the potential energy savings capability of a sampling of advanced lighting control systems from November 2015 to September 2017.  Advanced lighting control systems were installed along with LED fixtures and kits in five commercial buildings in the Northeast: two office buildings, a medical office building, a grocery, and a brewery.  The report provides descriptions of the sites, the control technologies, the data collection and analysis methods, and results. The researchers examined energy savings, cost effectiveness (in terms of simple payback and savings-to-investment ratio), and light levels. They also queried the occupants, installers, and operators for feedback on the installation process and lighting performance.

Control technologies installed included high-end trim/task tuning, occupancy controls, and daylighting controls. The energy usage of the original fluorescent lighting systems was measured to establish a baseline, then the existing light fixtures (primarily linear T8 fluorescent fixtures) were replaced with LED fixtures or LED replacement kits and advanced lighting controls and energy usage was again measured. The energy savings for the new LED systems and advanced lighting controls are shown in Table 1.

Evaluation Results at a Glance

Table 1. Summary of Energy Savings Across All Sites

 Site

 FL to LED

 High-End Trim/Task
 Tuning
 Occupancy
 Control
 Daylighting
 Control
 Total: LED with
 All Controls
  1 - Brewery    50%   negligible   10%   6%   66%
  2 - Office   64%   included in FL to LED   -2%   5%   67%
  3 - Med Office   29%   included in FL to LED   24%   9%   62%
  4 - Retail (Grocery)   30%   33%   3%   -   66%
  5 - Office   43%   24%   -1%   4%   70%
Note: Not all control savings could be separated at each site.

The findings are summarized below:

  • All sites vary in size, scope, and occupants, but the following conclusions can be drawn from these demonstrations: Every site showed energy savings, with savings ranging from 62% to 70%, and the bulk of savings came from the replacement of the fluorescent light sources with LED sources.
  • With rebates factored into the analysis, every project showed a savings-to-investment ratio of at least 1.0, indicating the project will just pay for itself over the estimated 20-year life of the system. Given that at the time of the installation the products were new and unfamiliar to the installers and the projects were not competitively bid, future projects are likely to be more cost effective.
  • Occupant satisfaction was generally higher post-retrofit in all categories, including satisfaction with the lighting, the automatic controls, and overall lighting conditions.
  • High-end trim/task tuning was shown to provide a large opportunity for energy savings from initial and ongoing light level adjustments in cases where existing conditions involved high pre-retrofit light levels, oversized LED replacement luminaires and lamps, and/or individual occupant preference or tolerance for lower light levels.
  • High-end trim/task tuning is a necessary step in a successful retrofit. For some of the sites, the equipment was tuned at the factory and thus savings are not parsed out in this study. In the two cases where tuning was actively measured, the results showed significant energy savings. When tuning a site, determine if the light levels from the new LED systems are appropriate or need to be adjusted.
  • The potential for energy savings based on occupancy controls may be reduced if the site already has occupancy sensors installed. However, advanced control systems can still provide a more uniform and smoother transition from occupied to unoccupied and back again, promoting better quality lighting for work environments along with granular sensing.
  • To ensure the same or better performance with new advanced occupancy sensors, it is important to ensure that the new occupancy controls are correctly commissioned with the lowest possible timeout settings and implemented with manual-on (vacancy) control where possible.
  • New equipment should be tested for compatibility issues and defects before doing large-scale installations. Products from two different manufacturers had issues with drivers (power supplies) to the LED fixtures during the demonstrations. One driver had a manufacturing defect; it was subsequently replaced, which corrected the issue. Another manufacturer’s driver emitted electrical noise that interfered with the control device signals. That manufacturer also rectified the problem.
  • Savings may not be realized if partial controls already exist on site or if there is limited opportunity at the site such as limited daylight. The cost effectiveness of advanced lighting control systems must be evaluated based on the true potential for savings at the specific site.

In general, the findings show that advanced lighting control systems can provide cost-effective energy savings and better control functionality but savings depend greatly on the existing site characteristics, including current lighting conditions and the existence of controls.

The demonstration projects were a joint initiative between the DesignLightsTM Consortium and the U.S. Department of Energy. The Advanced Lighting Demonstration complete report can be downloaded from the DesignLights Consortium website. Brief case studies of each site are also available.