Lighting Audits: Stingray Energy Systems LLC

Lighting Audits: What to Expect/Demand

A comprehensive lighting audit is crucial to a successful and optimized lighting retrofit. A thorough audit should cover a variety of topics, including: customer objectives, the physical and electrical characteristics of the existing lighting system and its performance, building attributes that effect lighting quantity and quality, the functional uses and visual tasks performed in specific areas, and factors effecting current operational costs and potential savings.

A successful audit starts with a survey of costumer objectives. While advanced metal halide technologies can provide dramatic energy savings, a lighting retrofit may also present a rare and valuable opportunity to address application-specific lighting needs. Customer experiences with the existing lighting system should be discussed and time should be taken to educate the auditor about the visual needs of the application. Are there areas or activities where employees struggle to see? Does glare complicate seeing? Are any fixtures especially difficult to maintain? As the audit progresses, a knowledgeable auditor will likely be able to offer suggestions and point out additional opportunities for lighting improvement.

Operating cost savings is the primary motivator behind the majority of lighting retrofits. In order to fully gauge the potential savings it is necessary to have an understanding of current operating costs. This requires a survey of the existing lighting system to establish the connected lighting load and its schedule of operation. It also requires an understanding of the utility rate structure and any additional electrical use charges. Unfortunately, it is not always straight-forward to interpret a utility bill in this respect. A lighting audit should include an analysis and explanation of utility charges and how they relate to the existing lighting system as well as any retrofit options being considered. Rate structures vary widely among utility providers and from one location to another. For many commercial and industrial customers electrical demand charges are a significant operating cost. These should be analyzed along with standard energy use charges to evaluate and maximize savings potential (this may require analysis of electrical use that is unrelated to lighting).

Various aspects of the existing electrical supply system must also be characterized, depending on client goals. Affected lighting circuits must be identified and their respective supply voltages established. This information will aid in the selection of suitable replacement options. When something other than a simple one-for-one energy-saving retrofit is desired, it may also be important to establish circuit capacities and loading. While an auditor should collect and use this information for the purpose of proposing alternative solutions, it is the facility staff’s responsibility to ensure that any modifications to its building electrical systems are conducted under the guidance of qualified professionals as dictated by local, state and regional authorities.

The auditor should determine whether the current lighting equipment has any special features or functions (such as enclosed-rated lensing and gasketing, dimming controls, emergency egress lighting, battery backup, quartz re-strike, etc.) and if these are to be integrated with or replaced by a potential retrofit system. The auditor should also interview facility staff to identify any special conditions that might affect or be affected by the lighting system (such as: corrosive atmosphere and materials compatibility, the presence of explosive gasses, excessive or oily airborne contaminants or moisture, food safety code requirements, high or low ambient thermal environment, etc.).

Staff should be interviewed with respect to the various functional areas of the facility and the nature of the visual tasks being performed. Illuminance measurements should be taken on workplanes corresponding to the primary visual tasks in each area. This allows the current light levels to serve as a frame of reference for the predicted values of a proposed retrofit system (see Interpreting Point-by-point Illuminance Predictions below). To put these values in context, the auditor should also interview staff regarding the adequacy of illumination for individual tasks and work areas. Qualitative aspects (such as glare, shadowing and uniformity) should also be discussed along with practical elements such as maintenance.

Existing light levels can also be compared to industry recommended values (see IES Recommendations). It is important to keep in mind that while inadequate illumination can have a host of negative consequences, over-lighting generally does not improve visibility in a significant way and represents an opportunity for energy reduction. A successful and responsible lighting retrofit should always preserve or increase lighting quality while reducing energy costs.

In order to accurately predict the illumination provided by a proposed retrofit, the audit must also include a fairly detailed survey of all the building features that affect lighting. Important factors include building shape and size, surface reflectance characteristics, luminaire locations, and the location and dimension of any objects that obstruct light (storage racks, partition walls, etc.).

When all is said and done, a lighting audit provides the basis for a retrofit proposal that is comprehensive, informed and responsible. Such a proposal should provide a clear description of the proposed retrofit system and detail all of the lighting (quantity and quality), energy, maintenance and financial implications.

Stingray auditor detailing lighting circuitry and loading