Difference Between Load And Line

As an important topic in the electrical industry, understanding the difference between load and line is essential for both electrical engineers and technicians. Load and line are two distinct concepts but are sometimes used interchangeably, leading to confusion. In this article, we will discuss the concept of load and line, their differences, and the importance of understanding them.

What is Load?

The load is an electric device connected to or used to power a circuit that consumes electric power. Examples of loads include appliances, heaters, motors, light bulbs, and computers, among others. You can categorize loads based on their characteristics, such as resistive, capacitive, inductive, or a combination of both.

Resistive loads consume power in a way that depends on the voltage and current supplied by the source. Examples of resistive loads include incandescent bulbs and heating elements. Capacitive loads store energy in an electric field, while inductive loads store energy in a magnetic field. Examples of capacitive-load devices include flash lamps and speakers, while electromagnetic loads include motors and transformers.

Load devices are the reason we need electricity: we use it for lighting, heating, running machines, and other purposes. Electrical currents flowing in the wires trigger these actions.

What is Line?

In electrical power transmission and distribution, a line is a conductor that carries electric power from a source to a load. There are two types of lines: supply lines and load lines.

Supply lines are the wires that carry power from the power plant to the substation. They have high voltages, typically ranging from 100 kV to 765 kV in the United States. High voltages are necessary to minimize energy loss and maintain a steady electric power supply over long distances.

Load lines connect the substation to the customer or equipment that needs the power. They have a lower voltage, typically ranging from 4 kV to 35 kV in the United States.

Differences Between Load and Line

The most significant difference between a load and a line is their function. A load is a device that consumes electric power, while a line is a conductor that carries electricity between a source (power station, substation, generator) and a load.

Another difference between load and line is their voltage rating. Load devices have a relatively low voltage and typically operate at less than 480 volts. On the other hand, transmission lines have high voltages in the range of thousands of volts to minimize energy losses.

Additionally, the loads are consumers of power, while lines are conductors of power. In other words, electricity flows from the line to the load. Load devices transform the electrical energy received into mechanical, thermal, or light energy, while transmission lines are responsible for delivering electricity through wires from the point of generation to the point of consumption.

Also, loads, which operate at low voltage, are connected to substation transformers where they are stepped down to the required voltage level for delivery, while lines operate at high voltage and transfer the current over long distances.

Importance of Understanding Load and Line

It’s essential to understand the difference between load and line to avoid confusion while working with electrical circuits. Electrical engineers and technicians should differentiate between both to ensure that the right voltage is delivered to load devices. Failure to understand the difference between the two can result in ineffective power delivery or even damage to the circuitry.

Additionally, understanding the differences between load and line is crucial when designing electrical systems. System designers must calculate current requirements for the devices used as loads and ensure the line carrying the current to them can meet those requirements.


In summary, the load and line are essential components in electrical circuits. The load is a device that consumes power, while a line is a conductor that delivers power from the source to the load. Understanding the distinction between these two terms is crucial for electrical engineers and technicians in ensuring that the right amount of power is delivered to load devices. Failure to understand the differences can lead to ineffective power delivery or damage to the circuitry, which can be costly.