In electrical terms, a load is any device or component in a circuit that consumes power. It’s the thing doing useful work: a light bulb converting electricity into light, a motor spinning a fan, a heater warming a room. Every circuit needs a load. Without one, you’d have a short circuit with current flowing freely and nothing to absorb the energy.
How a Load Fits Into a Circuit
Every electrical circuit has two basic parts: a source and a load. The source provides energy (a battery, a wall outlet, a generator), and the load uses that energy. Think of the source as a pump pushing water through a pipe, and the load as the sprinkler at the end doing something with that water. The load resists the flow of current and, in doing so, converts electrical energy into another form like heat, light, sound, or motion.
This relationship follows a simple rule: current equals voltage divided by resistance (I = V/R). The load’s resistance determines how much current flows through the circuit. A load with low resistance draws more current. A load with high resistance draws less. The power consumed by the load, measured in watts, equals voltage multiplied by current (P = V × I). So a 120-volt outlet powering a device that draws 10 amps is delivering 1,200 watts to that load.
The Three Main Types of Electrical Loads
Resistive Loads
Resistive loads are the simplest type. They convert electricity directly into heat. Incandescent light bulbs, space heaters, toasters, and electric stoves are all resistive loads. These devices have a straightforward relationship between voltage and current: they rise and fall together in perfect sync. When you switch off a resistive load, the current stops cleanly with no voltage spike or lingering energy. Resistance is measured in ohms.
Inductive Loads
Inductive loads use electricity to create magnetic fields, which then produce motion or transfer energy. Electric motors, fans, refrigerator compressors, and transformers all fall into this category. Unlike resistive loads, inductive loads cause the current to lag slightly behind the voltage. This happens because energy gets temporarily stored in the magnetic field during each cycle of alternating current and then released back. That back-and-forth creates what’s called reactive power, which doesn’t do useful work but still flows through the wiring. This is why motors and similar devices have a “power factor” rating, reflecting how efficiently they use the electricity they draw.
Capacitive Loads
Capacitive loads store energy in an electric field rather than a magnetic one. These are less common in everyday household settings but show up in certain electronics, power supplies, and battery chargers. In a capacitive load, current leads the voltage. Like inductive loads, capacitive loads involve some reactive power, though the phase relationship is reversed.
Linear vs. Non-Linear Loads
Loads can also be classified by how cleanly they draw current. A linear load draws current in smooth, even waves that mirror the voltage waveform. Traditional motors and incandescent bulbs are linear loads, even if their current is slightly out of phase with the voltage.
Non-linear loads, on the other hand, draw current in choppy, irregular patterns. Computers, LED drivers, variable-speed motor drives, and most modern electronics are non-linear. They pull current in short bursts rather than smooth waves, which distorts the electrical signal on the circuit. This distortion, called harmonics, can cause buzzing in audio equipment, overheating in wiring, and interference with other devices. The more non-linear loads you add to a system, the more voltage distortion builds up.
Measuring Electrical Load
The most practical way to think about load size is in watts, which represent actual power consumption. Common multiples include kilowatts (1,000 watts) for household appliances and megawatts (1,000,000 watts) for power plants. You can calculate watts if you know voltage and current: multiply volts by amps. A hair dryer pulling 18 amps on a 120-volt circuit consumes about 2,200 watts.
For context, here’s what different household loads actually look like in watt terms. On the low end: a desk lamp with an LED bulb uses about 5 watts, a Wi-Fi router about 15, a laptop up to 100, and a 55-inch TV around 120. On the high end: a washing machine draws around 2,200 watts, a hair dryer about 2,200, a kettle or space heater up to 3,000, and an electric oven up to 3,000. An electric vehicle on a slow home charger pulls up to 3,000 watts as well.
What Happens When You Overload a Circuit
Every circuit is designed to handle a specific maximum load. A typical household circuit in the U.S. is rated for 15 or 20 amps. If the combined load of everything plugged into that circuit exceeds its capacity, the circuit becomes overloaded. Overloaded circuits are a major cause of residential fires.
Warning signs of an overloaded circuit include:
- Flickering or dimming lights, especially when another appliance kicks on
- Frequently tripped breakers or blown fuses
- Warm or discolored wall plates around outlets or switches
- Crackling, sizzling, or buzzing sounds from receptacles
- A burning smell near outlets or switches
- A mild shock or tingle when touching an appliance or outlet
If you notice any of these signs, reduce the number of devices on that circuit. Avoid plugging high-wattage appliances like space heaters, hair dryers, or electric kettles into the same circuit as other large loads. Using a higher-wattage bulb than a light fixture is rated for is another common and preventable fire risk. Spreading your heavy loads across multiple circuits is the simplest way to keep your electrical system safe.