Consider the economics of replacing a 450w metal halide fixture. If an LED fixture can deliver the same lighting for an average of around 220w, the energy savings is about 50%, which would yield an annual savings of about $92 at 10 cents per kWh and 4,000 operational hours per year.
Considering the fixture replacement cost, many of these types of retrofits yield about a 5-year payback, although sometimes a utility rebate is necessary to reduce the upfront cost.
So, in this example, if you can get the LED manufacturer to guarantee a lamp life of at least 5 years, the LED would become practical. You may also be able to use the retrofit to obtain LEED points or achieve other green marketing initiatives.
Similar LED retrofits have been done on bridges and other outdoor applications with most utilities reporting success. In fact, one municipal client told me that after putting the LED lights on the bridges, they reduced their re-lamping interval so much that they had to conduct special bridge walks without actually re-lamping just to keep their maintenance staff practiced at high-wire walking.
LEDs are rapidly becoming effective replacements for HIDs, task lights, and other display lighting, especially applications in cold environments, such as refrigerated display cases. This summer, I did an audit of a well-known warehouse store and we found very short paybacks on replacing the fluorescent lamps with LEDs in the glass doors where they displayed milk and frozen foods.
Of course, there is variance in the quality of LED technology products. I have had one type in use for 2 years without a single failure, while I have also used other types that lasted about 2 months, so the guarantee and brand name may be an important consideration. When considering HID retrofits for indoor applications such as a factory or warehouse, the T-5 or T-8 (four tubes in a fixture) can also be very attractive and may have better economics.
One place where today’s LED technology has not created an attractive economic return is with LEDs in tubes to replace a T-8 lamp. The 13-15 watts per lamp sounds impressive, but at a cost of $50 per lamp, the payback is too long.
When you compare LEDs in tubes versus some of the low-wattage T-8 or T-5 technologies, usually the traditional solutions offer a quicker payback and higher reliability. However, progress is being made and the color of the LEDs in tubes is very good.
LED Technology in 2011?
While LED technology is making tremendous advances in sign-related lighting, HIDs, incandescent replacements and other “under counter” (display) applications; it has not yet become a suitable replacement for fluorescent tubes. This situation is likely to improve, but LED lights in tubes will also have to compete against other technologies that may offer a better economic justification.