Comparison of Various LEDs in MR 16 Fixtures with 55w Conventional Bulb

Hamilton Library on the University of Hawaii at Mānoa Campus has on its first floor a display area for small exhibits. The area gets a modest amount of natural light, and the walls are illuminated by 15 track lighting fixtures with the light provided by 50w, 12-volt incandescent MR-16 bulbs.

Because these fixtures cannot be turned off, they present an excellent opportunity for the application of LEDs.  LED bulbs are much more expensive than conventional ones ($20-$50 a piece) but because their energy use is ten times less (or more), they pay for themselves very quickly in “always-on” situations, such as exit signs, or in this case, poorly-conceived or non-existent lighting controls.

The total electricity use of these fixtures is approximately 6480 KWh per year (24 hours a day, 360 days).  The University’s electricity rate is $0.185/KWh – total electricity bill for these lights alone is $1,199 a year. Even if the LEDs replacing these bulbs cost $50 each, they would still pay for themselves in about eight months, expending only 389 KWh per year, or $72 for 3-watt bulbs, or more for 5-watt bulbs at $119. For reasons stated below, the 5 watt bulbs are looking increasingly like the option we will have to take.

The confusing thing about LEDs is that there are a number of different ways of measuring and evaluating their output, and even a careful reading of the product literature will not necessarily demystify the confusing array of descriptive standards and produce a clear picture of what the LED will look like. Therefore, to develop a better idea of what different LEDs would look like in Hamilton’s fixtures, a selections of LEDs were tested in the fixtures.  We measured lumens at a distance of approximately 3 feet from each fixture, and also took photographs.

The four LEDs tested were from Optiled www.optiled.com. Three were 3 watt bulbs, the fourth was significantly more powerful, at 5 watts. The 3 watt bulbs immediately proved to be more appropriate for less light-intensive applications. They were simply too dim to replace the 55w watt bulb. The 5 watt bulb approached the brightness we were seeking, but was too focused and too blue. (Fourth from the left is the original 50 watt bulb). The photograph exaggerates just slightly the color differential between the bulbs – the blues did not appear as blue in real life. Overall, none of the LEDs were suitable replacements for the existing bulbs, but it was a useful experiment that will inform future comparisons and the eventual change-out of these wasteful bulbs.

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