120 Volts vs 12 Volts vs 24 Volts: What Gives?
This week we’re gonna answer one of the most asked, yet elusive lighting questions in the industry: Why do certain lights operate on 120 volts versus 12 or 24 volts? And why does voltage even matter? It’s all about wattage, right? Not exactly. Lights operate on different voltages for specialized purposes, and in America, 120-volt, 12-volt, and 24-volt lighting systems are the most common. So what are the differences between them?
120 volts is the standard voltage supply for American homes. This is the voltage that travels to your home from your local utility substation. 120 volts is commonly referred to as “line voltage” by electricians and other industry experts. Nearly all indoor residential light fixtures and appliances in the U.S. run on line voltage. A 120-volt light bulb can typically be screwed into an indoor light fixture and operate correctly without further complication. Likewise, most appliances run on 120 volts and can simply be plugged into an indoor outlet.
Meanwhile, 12 volts and 24 volts are commonly used for outdoor lighting and are referred to as “low voltage” lighting. A transformer (or LED driver for LEDs) is required to "step down" (reduce/convert) the standard 120-volt supply provided to your home into a 12-volt or 24-volt supply for your lights. In most cases, whether you need a 12- or 24-volt light bulb simply depends on the needs of your light fixture: does your fixture require a bulb that runs on 12 or 24 volts to operate?
When it comes to LED rope light, or LED tape light for that matter, you may have the option to choose between a 12-volt or 24-volt light. The one you need depends on how long you need your rope or tape light to be. The longer your continuous strand of rope or tape light, the more voltage you will need to travel across its entire length without losing brightness (a phenomenon called voltage drop). We discuss 12V vs. 24V tape light further in our LED tape light guide.
The reason low voltage lighting is used outdoors is because it’s safer. If the wire for a 120-volt light source (which would run underground or on a building’s exterior, if used outdoors) were to become exposed, it would be very dangerous for someone to come in contact with, possibly resulting in a dangerous electric shock. For a low voltage light source, this risk is significantly reduced and would result in little to no harm in most scenarios. The rule of thumb: if your lights are being used somewhere where the wiring could become exposed, and therefore hazardous, it is always better to opt for low voltage lighting if given the choice.
These are just the three most common residential voltages in America. They are by no means the only voltages that can be used to operate lighting systems or appliances. Many US commercial buildings run on 277 volts, and in Europe, the standard voltage supply is 220 volts—a major reason why American appliances won’t work in overseas outlets. Some lighting systems require even more volts. When purchasing a new light source, first and foremost, you must always match your light bulb to the requirements of your fixture.
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