Line vs Load: In the electrical trades, the words “line” and “load” are short for the electrical wires that bring electricity from the source to a device (line) and the wires that send power to other devices further down the circuit (load). Incoming vs. outgoing wires, as well as upstream vs. downstream, are some of the more conversational phrases used to describe the same thing.

What Is a Line Wire?

The two words are used in reference to a single device and electrical box. The lines that deliver power into the box are referred to as line wires, upstream wires, or incoming wires.

What Is a Load Wire?

The wires that connect to other devices are referred to as load, downstream, or outgoing wires. These phrases refer to the device’s location in the circuit, as the load wire from one outlet becomes the line wire for the next receptacle downstream in the circuit.

The phrases “line” and “load” are used in a variety of contexts across an electrical system.

What’s the Difference Between Line vs Load Wiring?

An electric meter’s line side receives the utility company’s incoming feed. It feeds the line side of an electrical service panel or disconnect after exiting the meter from the load side. Line and load connections are also included on the service panel; the line supplies power to the main breaker, and the individual branch circuit breakers may be regarded as the load in relation to the main breaker.

How the Line and the Load Wire Can Be Distinguished

Position of the Wire
Because they are supplying power, line wires are typically located lower than load cables. Typically, load cables are placed close to the top of switches and outlets.

Wire Color: Typically, load wires are white, and line wires are black. This isn’t always the case, though. Think about more than just color when determining which wire is which.

Examining the Wire
To determine which wire is which, you can also use a multimeter and a non-contact voltage tester, among other tools. Think about one of these choices as well if you’re not happy with your results when you’re just looking at position and color.

When is it necessary to distinguish between a line wire and a load wire?

Circuits
On a single circuit, outlets (receptacles), switches, light fixtures, and other electrical devices are usually connected in multiples. The wire that connects the first device to the service panel is called the line, and the wire that connects the first device to the second device downstream on the circuit is called the load. The wire leading to the third device on the circuit is the load, the line is the power source entering from the first device at the second device, and so on.

The device itself can have the same meaning. The incoming source power is connected to the line side of an outlet. Power exits the device (or electrical box) and moves down the circuit on the load side.

Outlets for GFCI
When connecting ground-fault circuit-interrupter (GFCI) outlets, line and load have a specific significance. The screw terminals on GFCIs are labeled LINE and LOAD, respectively, and are used to connect wires. When the line terminals are connected, the outlet only offers GFCI protection for that outlet. That outlet and other standard outlets downstream on the same circuit are protected by GFCI when the line and load terminals are connected (using two electrical cables or two sets of pigtail wires).

Different Interpretations of Line vs Load

To differentiate the components of the circuit that are at full household voltage (typically 120 volts) from the low-voltage wiring and devices that are used after the voltage is stepped down at a transformer, the term “line” is used when wiring low-voltage circuits, such as those that supply doorbells or landscape lights.

The electrical demand, or power draw, that an appliance or gadget places on a circuit is also referred to as “load” in general. To get the “total load,” or maximum possible power consumption of all the lights on a lighting circuit, for instance, you can add up the maximum wattage of each light fixture on the circuit.

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