A Case against CFLs
Large incentives have been given to residential customers to adopt Compact Fluorescent Lights (CFL) in residential applications. Conservation groups and environmental agencies have also lauded their benefits in the home. And recently, large market forces have gotten involved in order to facilitate this transformation. All of this effort is in the name of energy efficiency. But are these bulbs really as efficient as they are made out to be; are they the answer to our energy woes? You would think from the claims that these “work horses of the lighting industry” are useful and equally efficient in any retrofit application. This is not the case though. These supposedly long-life bulbs are actually quite fickle. Especially in residential application, retrofitting can be considered ill advised compared to some of the alternatives. This document will explore some of the issues that CFLs have—especially in recessed down light applications, speak about how retrofits affect efficiency and discuss alternatives.
Light Output Equivalency
To target the retrofit marketplace specifically, manufacturers like to speak of output equivalency. They will say, for example that this CFL is equivalent to a 60 Watt incandescent bulb because the initial rated light output is similar to that of a 60 Watt incandescent bulb. There are unfortunately, no formal standards for this process, and there is nothing to keep another manufacturer from saying it is a 75 Watt equivalent. And indeed, this has been shown, in testing to be a problem. Almost systemically, manufacturers claimed a wattage step higher for their products than measurements supported in reality (O’Rourke and Figueiro, 2003). In other words, almost always when a CFL is labeled as an equivalent to a 60W incandescent, it is actually equivalent to a 40W incandescent in light output. This type of misinformation can lead to consumer dissatisfaction and policy based on false information.
CFLs ability to give off the rated light output has to do with its positioning. Whereas other technologies such as LEDs and incandescent can give off equal illuminance if mounted in any position, the position of the CFL is critical to the mercury vapor pressure inside the bulb. Reductions of up to 20% can occur in certain CFLs for horizontal or up and down orientation, but there is no standard between manufacturers and CFL types. Some CFLs like to burn horizontally, and some have optimal characteristics in an up or down orientation. This makes the job of finding the optimal CFL for the specific application, a difficult proposition for the end user and increases consumer dissatisfaction.
The light output and lamp life of the CFL is highly dependent on the ambient temperatures of the bulb (Ji and Davis, 2003). In recessed ceilings—the most commonly retrofitted application for CFL—the effects of temperature build-up in the cavity is immense. The relative light output decreases 10-20% for every 10 degree increase in ambient temperature above 25 degrees centigrade in the recessed housing, and, according to the National Lighting Product Information Program (NLPIP), “ambient temperature is almost always greater than 25 degrees centigrade”. In addition, NLPIP sites optical issues as a common “misapplication” of CFLs in recessed down lights. “Much of the diffuse light emitted by the CFL is absorbed within the luminaire” the report states. As a result, light that people think should be getting down to the work plane is not.
So just how much light is absorbed in recessed CFL retrofits. According to the testing done by NLPIP, starting with an average efficiency for CFLs tested of 69 lumens/Watt, placing CFLs into recessed ceiling cavities brought their efficiency down to 51% on average to 35 lumens/Watt. At this efficiency, the bulb not only does not have superior efficiency characteristic, but it no longer qualifies for certain energy efficiency programs, which promote its use in retrofits for residential applications. In addition, NLPIP reports that on average the use of CFL in this application reduced illuminance efficiency by an additional 14% (down to 25 lumens/Watt) because of the thermal issues discussed above.
CFLs, because of their average dimensions, are usually too long for recessed luminaires and extend below the ceiling plane. This causes glare. CFLs in recessed applications put more illuminance on the walls (angles above 50 degrees from nadir) than in the desired plane of directly below. Not only does this lead to low coefficient of utilization readings (CFLs do not effectively get light down to the work plane), but it becomes a source of glare as well (Ji and Davis, 1993). Eye strain and the poor color rendering properties of CFL lead to further consumer dissatisfaction.
Unlike other technologies such as LED and incandescent, CFLs need very particular conditions in order to start up and continue operation. Initial high voltages are necessary for striking the lamp and maintaining the mercury vapor pressure in the bulb as it burns. Much of the bulb technology goes into building support mechanisms for mercury vapor pressure building and maintenance. Since this takes time relatively speaking, frequent switching of CFLs is a bad idea. It reduces their lifetime and effectiveness. CFLs are “not recommended in spaces where lights are turned on and off frequently”, according to NLPIP, such as bathrooms, closets, hallways (or in a word: homes) where recessed and other CFL retrofits are common. For uses in commercial applications, where the lights will be on for hours at a time, CFLs can be a viable alternative. In homes, however, there are better technologies to deal with frequent switching.
The push to replace incandescent bulbs is a good thing. No one is going to argue that Edison’s A-lamp, which is only 10% efficient, is anything but an anachronism, needing to be replaced in the average home. The promise of CFLs being the final answer, however, is dim based on the issues discussed in the document. While government agencies, environmental groups, politicians and manufacturers push what they see as the only alternative, CFL, developments are being made in solid state lighting, which makes it a much more viable alternative in residential applications. General lighting in the home should be dimmable. It should be able to withstand frequent switching. It should put the light where you need it and have superior color properties. It should be comfortable to look at and have a long life. In all of these categories, the CFL fails in comparison to our products. When the only factor, efficiency, proves to be false in its most common retrofit application, the case of the CFL for residential use is a difficult one to support. Ultimately, the consumers will decide, despite all the pressure, whether to accept CFL or not. So far they have said unequivocally “no.” In the meantime, it is important for all the forces that are pushing CFLs in the first place to be educated on LEDs and understand that there are viable products in the marketplace already, which can reduce energy demands and satisfy the aesthetic and practical lighting needs of the end user.