Posted on March 02, 2011

Beware of Making Comparison Mistakes With Halogen Lamps

We recently evaluated the Solais LED LR38 (21W, 1000 lumens) against a PAR38 halogen (90W, 130V, 1310 lumens) for a high-profile client. The client had some initial concerns due to the apparent large difference in lumens between the two products, but this was simply because they did not have a proper understanding of the importance behind the 130V rating. After educating the client about how the halogen lamp decreases to 79W and 1000 lumens at 120V (standard line voltage), we realized how common of a mistake this must be in the industry.

Why is this important?

Many commercial applications use 130V halogen lamps and customers assume there is no equivalent LED upgrade because of the high lumen value published for the halogen lamp. Looking deeper into the spec sheets/product literature, one can find the manufacturer's notes on what the lamp specs will actually be when powered by standard line voltage.

Why does this happen?

There is a very basic electrical formula that states: wattage (W) = voltage (V) x current (I). Halogen lamps heat a metal filament to produce light. In a metal, voltage and current have a linear relationship. This means that when a lamp is designed to 130V but is put onto a 120V system, the wattage will decrease in a linear function (To be completely accurate you need to account for the resistance of the filament, which is a function of its temperature to the 4th power, but this is not necessary for arguments sake). As the wattage decreases, so does the lumen output.

So why would they design halogen lamps to 130V?

AC voltage is quite unpredictable and can vary depending on geographic location. In a typical 120VAC line, surges or spikes in voltage can occur and a lamp made to 130V will help protect against failures. Additionally, certain regions of the country actually have higher standard voltages (up to 130V). Designing lamps to be 130V is also a common technique used because when a 130V halogen lamp is used on a 120V system, it increases the life of the lamp (In our specific case, the life was increased from 2500 to 5000 hours). Like most things however, there are trade-offs and in this case the lower voltage also reduces the efficacy of the lamp.

What does this really mean?

As a customer there are two key points you must understand for this situation:

1 If you use 130V PAR lamps, remember that their actual lumen output on standard line voltage is significantly lower than the published specs. This means that high quality, high output LED lamps like those provided by Solais ARE and equivalent upgrade.

2 When evaluating your energy savings by switching to an LED lamp, especially when it is provided to you by the LED manufacturer, make sure they to account for the correct wattage of the halogen lamps. If 90W (@130V) is used instead of 79W (@120V), more savings will be shown then you will actually receive.

About PowerSecure Lighting: PowerSecure Lighting designs and manufactures the lighting industry's highest-performing LED lamps and fixtures. With superior lumen output, center-beam candlepower, and overall aesthetics and performance, PowerSecure Lighting's LED products enhance the retail, supermarket, commercial, museum and hospitality environments of the world's leading brands. PowerSecure Lighting relentlessly pushes the innovation envelope to create products that replace traditional lighting technologies with zero compromise to aesthetics and performance. To learn more about PowerSecure Lighting, visit us in person in Stamford, Connecticut, or online at PowerSecureLighting.com.

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