Energy Efficiency Consulting Firm

LED Basics


Light Emitting Diodes, or LEDs, are used in a number of household applications, from displaying numbers on appliances and clocks to transmitting information from your remote to your television. Out in the world LEDs are collected together to make high visibility traffic signals and large television screens.

An LED is termed a solid-state lighting technology. Where as an incandescent or fluorescent light bulb uses a vacuum or a gas to produce light, an LED relies solely on solid matter, hence the name “solid-state”

LEDs are, more or less, little lights that fit well into a circuit. What sets them apart is that LEDs do not rely on a filament for light. Instead they combine two semiconductors, a negative one with excess electrons and a positive one with holes or openings for electrons. When stimulated by an electric current, electrons from the negative side get excited and flow into the holes on the positive side. As they do this they emit photons in the form of visible light and that is what we see.

  …LEDs eliminate some of the biggest downsides of incandescent and fluorescent lights…

Since LEDs do not have a filament, they eliminate some of the biggest downsides of incandescent lights. For one, getting rid of the filament cuts down on the excess heat produced in keeping the light on. A typical light bulb with a filament relies on heating up the filament via electric current to produce light. This is also why they are so inefficient. The filament requires a constant input of electric current to maintain its brightness and white-hot glow. An LED just requires a slight current to keep the electrons flowing. One of the biggest problems in the past with using LEDs in a home environment is that some of the light gets trapped inside due to its structure. This causes the actual useful light to be somewhat dim.

In the past several years, however, this problem has been solved. Now it is possible to find an LED replacement bulb with the equivalent output of a 60-watt incandescent bulb, all the while using 8 times less power. The LED replacement bulb can achieve that 60-watt equivalence using only 7.5-watts.

Energy Consumption

Over the course of a year, a 60-watt light bulb that is on 10 hours a day will cause nearly 300 pounds (136 kg) of CO2 emissions. The equivalent LED, which is only a 6-watt bulb, will cause 37 pounds (17 kg) annually. By replacing all existing incandescent lights with LEDs, the carbon footprint of a given building can be reduced by up to 85%.

Economic Sustainability

LED lights are a plausible lighting option economically due to their long lifetimes. Just a few years ago the feasibility of using LEDs was limited by their high initial price and their low efficacy (lumens per watt). More recently, though, the efficacy of LEDs has increased dramatically. Now LEDs are available as high as 150 lm/W with the inexpensive models reaching as high as 60 lm/W, which is the equivalent of a compact fluorescent. With the extended lifetime and the recent increase in efficacy LEDs are a sound investment.

Today a 7.5-watt LED light bulb can output the equivalent of a 60-watt incandescent light. In addition to the decreased power required, maintenance is also minimized thanks to the dramatic increase in lifetime of an LED. A 60-watt incandescent light has an expected lifetime of 1,000 hours while an LED can operate for over 50,000 hours.

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