Understanding the Operating Voltage of Streetlights in the USA

The operating voltage of streetlights in the USA can vary based on the specific design, installation requirements, and the size of the application. Typically, residential streetlights are designed to operate at 120 volts, while larger or more industrial applications, such as those found on highways and in industrial areas, may use 240 or 480 volts. Additionally, some LED streetlights, especially solar-powered ones, can operate on lower voltages such as 12 or 24 volts.

Large-Scale Installations and Residential Areas

Larger-scale installations typically use 480 volts, three-phase feeds, with individual luminaries receiving 277 volts from one phase to neutral. In residential areas, the luminaries are commonly 120 or 240 volts, single-phase. For older highway lights and airport runway lights, voltages can reach 5,000 volts in series circuits, fed from a constant current transformer.

Historical Context and Series Wiring

Historically, streetlights were wired in series, which meant up to 40 lights in a string could be lit at 50 volts per light, requiring a total of 2,000 volts or more. The current was usually constant at 6.6 amps, and there was no loss of voltage at more distant lamps. A current regulator supplied the loop, and a special shunt would short out the fixture if a bulb failed. While series wiring is less common today, it is still used for airport runway and taxiway lights. As of recent technologies, such as mercury vapor lamps, series circuits are still used.

Economic Considerations

Residents typically pay the electric bill for streetlights in their neighborhoods, while larger streets, such as those in counties or cities, are funded through taxes. The USA invests a significant amount of money in street lighting, even on its interstates, which have streetlights.

240VAC and Series Wiring

Some streetlights do run on 240 volts, particularly in series with other lights on a 1300-volt line. However, it's less common today. One can remember how all the lights on a street would come on simultaneously in the 1940s, a phenomenon changed with the advent of Red Ryder BB guns. Modern streetlights are more efficient and less dependent on historical series wiring methods.

In summary, the operating voltage of streetlights in the USA can vary greatly based on location and application. Understanding the different voltages and their implications is crucial for effective streetlight design and maintenance.