Get Clarity on NLC Energy Savings Potentials

Back in 2020, the Northwest Energy Efficiency Alliance (NEEA) and the DesignLights Consortium (DLC) published a report titled “Energy Savings from Networked Lighting Control (NLC) Systems With and Without LLLC”. One of the main objectives of this report was to quantify average networked lighting control (NLC) energy savings to facilitate and accelerate the inclusion of NLC measures in prescriptive energy efficiency programs.

While NEEA and the DLC are thrilled to have made such significant contributions to the industry with this report, they discovered that, in some cases, the presented information was interpreted differently than intended by the two organizations. Confusion might have arisen due to ambiguous descriptions or key points not prominently highlighted in the report, which could introduce challenges for the information in this report to be more widely adopted.

NEEA and the DLC followed up on the original report by interviewing utility energy efficiency program stakeholders to identify where the report could use clarifications and improvements to facilitate wider adoption. The findings from this project were documented in a memo, and an updated executive summary and errata were issued to amend the original 2020 report.

The 2020 report estimated an average energy savings of 49% for NLCs overall, and 63% and 35% average savings if broken out to NLCs with and without luminaire-level lighting control (LLLC) capability, respectively. These savings figures, also known as control savings factors (CSFs), quantified in the report would be directly utilized by prescriptive programs in their savings claim filings or serve as the basis for specifying claimable NLC savings in Technical Reference Manuals (TRMs) or equivalent documents, which are the primary reference for prescriptive programs. Since its publication, the report has influenced TRMs and efficiency programs in 21 states and provinces across the United States and Canada, as noted in a 2024 research project commissioned by the DLC as a member-exclusive resource (Dan Mellinger, PE, LC, Energy Futures Group).

The memo provides a revised Executive Summary to the 2020 report and clarifies the following questions identified as common sources of confusion in the original 2020 report.

What types of LLLC are the CSFs applicable to?

The CSFs are most applicable to LLLCs that conform to the DLC’s definition of LLLC. (The DLC considers luminaire level lighting controls (LLLC) to be a subset of networked lighting controls (NLC).)

To what extent must the NLC systems be programmed and commissioned so the CSFs can be applied to a prescriptive program?

The CSFs represent the savings potential averaged across NLC systems with various degrees of system programming and should not be construed as the maximum achievable savings with optimized system programming.

Why would the savings be significantly higher or lower than the reported CSFs when energy savings are quantified from a sample set of a program’s project portfolio through an M&V effort?

Savings derived from a small sample set of NLC projects could drastically differ from the CSFs documented in the report because the data has a large variance; therefore, a small sample may be biased by one or two extreme values within the sample set.

Why aren’t the CSFs broken down by control strategies in the report adding up to the overall average CSFs?

In addition to the average overall CSFs, the report provided CSFs broken down into high-end trim savings and “other control strategies”. The “other control strategies” savings generally encompass savings from occupancy sensing and high-end trim combined. The broken-down CSFs are meant to represent savings potential from the two sources, namely high-end trim and “other control strategies”, independent of each other. We believe this is a more pertinent presentation of the broken-down CSFs as it conveys the true savings potential of the two control savings sources without being contingent on each other. An alternative conveyance of the broken-down CSFs that will add up to the overall CSFs can be derived from the CSFs presented in the main tables of the report. The derivation is provided in the report appendix.

What do the CSFs represent when broken down by building types?

The report provided CSFs broken down by building type to show how the estimated savings vary with building type. The broken-down CSFs were derived from energy data of NLCs that serve the entire facility, including the primary function areas and all supporting spaces. Therefore, these CSFs should represent the average savings potential of a building in its entirety, not just the main functional areas. The CSFs should not be treated as the savings potential of any specific functional area.

Why does another 2020 NEEA report, titled “Luminaire Level Lighting Controls Replacement vs Redesign Comparison Study”, say that NLCs with and without LLLC have indistinguishable savings potential while this report estimated much higher savings potential for LLLC?

It would not be an apples-to-apples comparison by simply putting the conclusions of the two reports side-by-side without context. The other NEEA report compared the control savings between several one-to-one LLLC replacement scenarios and a lighting redesign scenario using an NLC without LLLC. This NLC implementation was essentially optimized for luminaire layout, sensor placement, and system programming to maximize energy savings. On the other hand, the NLC without LLLC savings estimated in this report is the average across systems spanning a broad spectrum of design and control optimization.

How confident can the industry be when utilizing the CSFs and other information, given that one of the report findings recommended additional studies to verify the estimated CSFs?

Calling for continued studies does not imply a lack of confidence in the CSFs estimated in the report. The CSFs were derived from a meaningfully large and diverse set of measured energy data. Technology will advance over time, and different data sets could further mitigate any bias that might exist in this study’s data set; therefore, it would be prudent to encourage future studies to update the current findings.

By clarifying these questions, the DLC and NEEA hope to address doubts that utility and energy efficiency program stakeholders have when considering referencing the report for estimating claimable networked lighting controls energy savings. More detailed answers to the questions can be found in the memo.