In this pilot project, the study was restricted to lamp-ballast retrofit kits and complete luminaire replacements that would preserve the daytime appearance of the existing acorn-style luminaires. This challenge proved formidable, as the results indicate that none of the LED products evaluated could match the performance of the existing 100W high-pressure sodium (HPS) luminaires. The report, available for download, highlights some of the nuances involved in LED product selection.
To allow for apples-to-apples economic comparison, the pricing and input power of the LED products had to be scaled proportionately to represent hypothetical products which could match light levels from the HPS fixtures. Energy used by three of the scaled-up LED systems ranged from 63-90% of the baseline HPS. The fourth product would actually require an increase in energy use by 15%. None of the products would represent cost-effective alternatives to HPS.
In response to recent industry developments, the study also investigated the relative significance of mesopic multipliers offered in the new IES Lighting Handbook and the lumen maintenance extrapolation methodology offered in the new IES TM-21.
This pilot project is the first in a series conducted by the DOE Municipal Solid-State Street Lighting Consortium, which serves as an objective resource for LED product evaluation and a repository for valuable field experience and data. The data generated from this project may be useful to standards groups, manufacturers, and those considering retrofits to LED.