It’s now high time to switch on to awareness of upcoming new residential lighting energy efficiency standards, and their impact for homeowners due to progressive federal and local energy codes and green building programs. If you’re still in the dark about CFLs and LEDs, lumens, CCT and CRI, this article will be of timely help. Consumers may go through a large learning curve with a more complicated selection process, but the brighter long-term news is good for cost savings and our environment.
That’s because the federal Energy Independence and Security Act (EISA) of 2007 takes effect Jan. 1 2012. The legislation will soon limit the number of watts any light bulb can consume for a given number of lumens, a measure of light output. The luminary output equivalent of today’s 100w incandescent bulb will be allowed to consume only 72w (of course, other size bulbs are affected proportionately). Doing the math, that means incandescent bulbs need to get 28% more efficient. That may occur, but probably at increased cost. Regardless, the long-term outlook for incandescent bulbs is dim.
Familiar and affordable, incandescents have super hot glowing electrified filaments that produce a warm white light. However, they are inefficient, as up to 95% of their energy converts into heat. In fact, incandescent bulbs are now banned in Brazil, and are being phased out in Europe. Used responsibly in the U. S., such as with dimmer switches, they can still provide good overall ambient light. They have an efficacy of between 10 and 20 lumens per watt (lm/w).
Halogen lights are a more refined and (relatively) efficient version of incandescent bulbs, operating at an even higher temperature using tungsten filaments and inert halogen gases. Their crisp white light and concentrated beams are best used for accent and task lighting such as art highlighting and under cabinet lighting. Some types of bulbs are dimmable.
Energy efficient compact fluorescent lights (CFLs) and light emitting diodes (LEDs), now a relatively small segment of the incandescent bulb-dominated lighting market, are about to get a significant boost in use, because they already meet the new EISA standard. Dramatically more efficient, CFLs have an efficacy range of 60 lm/w to 100 lm/w, and LEDs now measure in the range of 70 to 80 lm/w, but are projected to exceed 150 lm/w by 2015.
All light bulbs produce a range of light quality measured as correlated color temperature (CCT), in the spectrum of white light from “warm,” which has a yellow-gold hue, to “cool,” which has a bluish cast. Lower numbers are associated with warmer light and higher temperatures are associated with cooler light. People look best under warmer home lighting of 2700 degrees Kelvin to 3000 degrees K. Incandescent lights have a temperature of about 2700 degrees K, and neutral office fluorescent bulbs have a temperature of around 4100 degrees K. Another measure of light quality is color-rendering index (CRI), how well a color is rendered or shifts under different artificial light sources compared to natural daylight, on a scale of 0 to 100.
Available for nearly 20 years, CFLs have been steadily improved and now have arrived. Electrically excited mercury vapor creates ultraviolet light which causes a phosphor to fluoresce, producing visible light. Ballasts regulate the flow of electrical current. Startup times are improving to the extent that instant-on CFLs will soon become available. New electronic dimmer switches must be compatible with new CFL electronic ballasts, however, light may cut out before dimming all the way down. Otherwise, any CFL used with a dimmer isn’t dangerous, it just won’t dim. Good CFLs have a CRI above 80. Most CFLs provide excellent ambient, accent, and task lighting. Cost of a typical coiled 19w CFL may be $3.50.
An Energy Star qualified CFL bulb should save about $30 over it’s lifetime and pay for itself in about six months because it uses 50-80% less energy and lasts about ten times longer than an incandescent bulb. Initial cost is higher, but don’t buy cheaper house brands using inferior phosphors that create poor CCT hues.
In five to ten years, most light fixtures will house light emitting diode (LED) bulbs, which use glowing computer chips grouped together for illumination, instead of filaments or gas. Electricity regulated by drivers runs through the chips, exciting electrons and producing light. LEDs don’t actually produce white light; it must be created either by combining chip colors or using a phosphor. LEDs produce heat and require thermal management with use of a heat sink, usually aluminum fins. Currently, cost is the biggest factor in LED use, but like computer chips using Moore’s Law, prices should fall by a factor of 10 while performance increases by a factor of 20 over the next decade. Currently, the cost of a screw-in LED recessed can replacement costs about $120. LED standards for CCT and CRI have so far been voluntary, and variable between manufacturers, as has been switching and dimming response, so evaluate these products carefully. Most LEDs are good for directional accent or task lighting.
Both CFLs and LEDs are now available with dedicated fixtures that can lengthen the lifespan of the bulbs and maximize their attributes. However, CFLs, needing time to attain full brightness, are not appropriate where lights will be switched on and off frequently and quickly, reducing bulb lifespan.