The High Price of Light: How Efficient is Your Interior Lighting?
Posted on 19. Jul, 2010 by keith in Sustainable Building
The price of having inefficient interior lighting can be deceptive. While a single fixture results in almost no energy cost, a recent study shows that the fixtures in a commercial building account for 38 percent of its annual electrical usage, which can equal out to thousands of unnecessary energy dollars when the fixtures are inefficient. There are two aspects that determine whether interior lighting is efficient: its wattage, and how well it retains its brightness. Based on wattage and brightness, the two most inefficient forms of lighting in U.S. buildings are metal halide lighting and fluorescent T-12 lighting.
Initially, metal halide lighting burns brightly and is relatively energy efficient. But after only 60 percent of its useful lifespan, it loses over 40 percent of its brightness, making work areas appear dim and potentially posing a safety hazard. Like metal halide lighting, fluorescent T-12 lighting also goes from being bright and relatively energy efficient to being not so bright, losing 20 percent of its brightness after 7,000 hours of use. After decreasing in brightness, metal halide lighting and fluorescent T-12 lighting continue to burn at their original wattage, making them incredibly energy inefficient.
The ideal answer to metal halide and fluorescent T-12 fixtures—and incandescent fixtures, for that matter—is to replace them with more efficient fixtures, such as fluorescent T-8 fixtures. Instead, some companies implementing lighting control systems, which reduces annual utility costs but doesn’t address the true problem. A better practice is to replace inefficient fixtures and implement a lighting control system at the same time. When they do, companies save the most money of all, regularly reducing the annual cost of their interior lighting by more than 50 percent.
