LED streetlights

Efficiency

Interesting factoids about replacing sodium vapor lamps with LEDs for city-wide lighting.

• The theoretical lumen/Watt figures for LEDs are worse than low-pressure sodium vapor lamps (100 lm/W versus 200 lm/W)
• White LEDs are actually blue LEDs with a consumable phosphor layer that turns opaque after a few years of operation.
• Combined RGB LEDs will have better efficiency than a "white" LED.

Other real-world tests have concluded that LED street lights have about the same lumen/Watt in practice as the sodium vapor lamps (64 lm/W LEDs versus 67 lm/W Sodium vapor).

Neon and florescent efficiency depends on the color and shape:

[...] the fluorescent tube produces between 50 and 100 lumens of light per watt depending upon design. Compare this with the typical incandescent light bulb that produces between 10 and 20 lumens per watt. Neon light efficiency is based upon much fancier pants, the color of its output, which ranges from 10 lumens per watt for red to 60 lumens per watt for green or blue. One reason that green and blue tubes are more efficient is that phosphor coatings used to produce such colors better ballyhoo the high-energy ultraviolet light from the argon/mercury mix into visible colors. One reason that the fluorescent tube is more efficient than a neon tube is that a large straight tube offers less resistance to electrical current flow than a skinny bent one.

Obstacles

Little Rock, AK wanted to replace their inefficient shielded lights with more efficient fixtures, but their contract with Entergy is not a simple $/kW formula: the energy company sets the price based on the type of fixture.

[...] According to Henry, the city tested out more efficient 100–watt HPS bulbs in one Little Rock neighborhood about five years ago. When the city asked Entergy to set a rate for those fixtures, it was almost double the rate for the 150-watt HPS type.

When asked if Entergy was keeping Little Rock from being more energy efficient, Henry said simply, "Yes."

"But how do you fight Entergy?" Henry asked. "I mean, we've had people come in and show us new, more efficient lights and we've said, well, the problem is, it's not going to save us anything. It will be a whole lot less wattage and it will put light out on the street but we can't get any benefit out of it because of the tariffs."

Commercial LED lamps

SparkFun sells LED lamps that are screw compatible with US light sockets:

• 75 W
• 12 W
• 3 W
• 1 W