LEDs still have a way to go before they can serve as a one-for-one replacement for conventional lighting.
That might be one conclusion to be drawn from a recent Dept. of Energy report dubbed Laboratory Evaluation of Light-Emitting Diode (LED) T8 Replacement Lamp Products. The DoE testers looked at products designed to directly replace linear fluorescent lamps (most commonly called T8 lamps) in commercial ambient lighting. DoE checked three products considered among the “best in class” at the time of the study, according to DoE’s CALiPER testing program.
DoE says the power reductions associated with LED T8 replacement applications frequently come at the cost of significant reductions in lumen output. DoE tests used a two-lamp prismatic lens fixture. All three LED products drew less power than their fluorescent counterparts but, like others of their kind, also put fewer lumens on the work surface. DoE also says the prices of the LED products are such that none pay for themselves when compared to the standard T8 fluorescent lamp used as the primary baseline in the study.
The study, run at the Pacific Northwest National Laboratory, concluded nevertheless that LED T8 replacement products come close to competing with typical fluorescent products in raw efficacy. However, DoE says LED products show mixed results when built into fixtures. Tests of prismatic and parabolic troffer applications showed that the LED products delivered a lot of light. However, in a “basket” fixture, they do not perform as effectively. In all cases, total light output is lower.
But the report points out that many real-world applications are over-lighted. Here, the lower output of LED replacements can provide appropriate light levels at lower power levels. Problem is, you could get the same result more cheaply with lower wattage fluorescent options which would also put out more light over the product’s lifetime.
DoE testers also say it is worth noting that new approaches and LED product designs are continually emerging. Alternative designs, such as panel-type products and overall troffer replacement systems, may prove more effective, they think, in the future than the products tested in this study, which are designed to substitute for fluorescent lamps in existing troffers. For this study, DoE didn't evalute any of these alternative whole-luminaire designs.
You can read the whole study results here: http://apps1.eere.energy.gov/buildings/publications/pdfs/ssl/gateway_t8-replacement.pdf