October 2019 EnergyWiseSM Tip: From Dusk ‘Til Dawn



By: Energy Efficiency Program Manager Cory Fuehrer

While the Halloween season and this article’s headline may make some horror movie fans wonder if I am going to share an energy-efficient way to rid your place of vampires, this real-life tale might be even scarier if you still use mercury-vapor lights to cut through night’s darkness. If you are one of the unsuspecting owners of the thousands I still see during my nocturnal travels throughout Nebraska, the following facts may leave you screaming in horror!

Cost of Operation

Let us "cut" to the chase. Mercury-vapor lights are expensive to operate. The standard 175-watt mercury-vapor lamp requires a fixture with a ballast to operate. Most people do not realize the ballast uses energy too. So in reality, it takes 205 watts to illuminate one bulb. Operating an average of 12 hours per night, over the course of one year, will use 898 kilowatt-hours (kWhs) of electricity. Using Nebraska’s average residential rate of 12.4¢/kWh, that costs $111.35 every year. Judged against light-emitting diode (LED) fixtures, a 50- to 75-watt LED will provide comparable lighting levels for only one-quarter to one-third the energy use.

Longevity of Useful Light

Looking at a mercury-vapor lamp’s estimated lifetime, one might think 24,000 hours is a long time, but it’s little more than five years when averaging 12 hours per night. After six years, some may think, Hey! This bulb is lasting longer than they said it would! That is because mercury-vapor almost never dies! But, sometimes a DEAD light bulb is better than one that just gets dimmer and dimmer while devouring the same amount of electricity! After only the first year, mercury-vapor lights have lost nearly 20 percent light output. By comparison, LEDs lose less than 2 percent over the same period.

False Sense of Security

Many feel an exterior light burning "from dusk till dawn" will dissuade criminals from approaching. However, the glare produced by mercury-vapor can create harsh shadows to hide in and, if reflecting off a shiny surface, can "redline" surveillance cameras. Security experts agree that a motion-sensing LED floodlight in the 100- to 200-watt range is far more effective. Its sudden brightness will startle intruders and produce less-predictable shadow patterns. Not to mention, werewolves hate LEDs.

Attracts Critters

Most insects, including the bloodsucking ones, are photophilic, which means they are attracted to light and especially light in the ultraviolet spectrum. Mercury-vapor bulbs are great at creating ultraviolet (UV) light! Not long after these pests show up, the other creatures that prey on them, like spiders, bats, rodents and snakes show up for the "all-night" buffet you provided. Some outdoor LED fixtures are created to generate no or very little UV. Thus, they attract fewer types of bugs. Simple equation: Less bugs = less buffet = less icky critters.

Light Pollution

"Big City" dwellers often forget what the night sky is supposed to look like until they visit the country. Why can’t anyone see the stars in downtown New York? All the man-made light drowns them out. Mercury-vapor, like high-pressure sodium and metal-halide bulbs, emit light in nearly all directions. Though fixtures help direct the light to where it is desired, the majority is wasted as it overwhelms the sky, creates driving glare for passers-by or keeps a nearby neighbor up all night as it shines through their window. Since LEDs create directional light, it is easier to focus the light where it is needed most. This is especially beneficial if you live next to a cemetery. No reason to let ghosts and zombies you live in the neighborhood.

Southwest Public Power District and Nebraska Public Power District want to help you make the most of the energy they provide you. That includes illuminating your darkest nights and keeping the nocturnal bloodsuckers away. For assistance on making your home EnergyWiseSM, contact Southwest Public Power or visit www.nppd.com.

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