Dispelling the “Inefficient Neon” Myth part II

Watts per foot

For linear light sources such as neon, watts per foot is sometimes used as a measure of energy consumption. Note that this measurement does not have a lumen component and tells us nothing about how bright a sign may be.  For example LED channel or border lighting may have a lower W/ft rating compared to the neon equivalent, but yields far less light because it is a less efficient source. Watts per foot figures for LED modules can also be misleading since they depend on how the modules are laid out. One manufacturer provides a guide on its channel letter module spacing and expected sign brightness; for its green LEDs the recommended layout to achieve only 45% of the brightness of rare-earth green neon (green acrylic face) results in an energy usage of 9.9 W/ft.  Using its high output white LEDs (white acrylic face) results in a consumption of  11.9 W/ft and a sign only 80% as bright as that with 6500K rare-earth white neon. The neon in both cases, when powered with electronic transformers, would consume around 3.5 W/ft. A study of channel letter lighting by the Lighting Research Institute found that to produce the same amount of light, white LEDs consumed 2-8 times more energy than standard 6500K Snow White neon (30mA ferromagnetic transformer). If a white tri-phosphor and electronic transformer had been used in this comparison, the difference would be even greater.

For the currently available range of LED channel letter modules, only red is able to approach neon in terms of brightness and energy efficiency when used with certain, sometimes specially developed, red acrylic faces. Red (clear) neon has an efficacy of approximately 10 lm/W and a power consumption of 3.5-4 W/ft when run on an electronic transformer. The corresponding figures for the best red LED units used in sign applications are similar at 11 lm/W and 3 W/ft. This small difference is in stark contrast to the often quoted statement from LED proponents that the use of LEDs can result in 90% energy savings. For this to be the case, a red LED would need to have an efficacy of 100 lm/W, or in terms of energy use, the neon would need to consume 30W/ft!

If in doubt- prototype

Whether illuminating channel letters or lighting borders, high efficiency, rare-earth based phosphor neon will almost always result in the brightest, most energy efficient signage, especially when used in combination with electronic (solid state)

transformers. Although these phosphor products have been available for several years, there has been a certain amount of resistance to their use from sign companies, due mainly to perceived cost issues. Rare-earth (tri-phosphor) coated tubing may cost double that of standard tubing, but when put in the context of a completed sign the increase is minimal, around 30¢/ft, when compared with the benefits its use brings. In many cases it may be required for a specifier to directly request that the sign company uses these products. If any doubt exists as to the best illumination solution, the coated tubing manufacturer should always be available for consultation and to provide appropriate samples for test. Prototype building is sometimes necessary - in fact this is to be encouraged, since it allows different products to be compared. For example for channel letters, the sign can be scrutinized for pantone color match, comparative surface brightness can be determined with a relatively simple light meter, and power draw (real and apparent) measured with one of any number of commercially available power meters.