Voltage Drop Calculator
Use this calculator to determine the voltage drop and percentage voltage drop in an electrical circuit. Understanding voltage drop is crucial for ensuring efficient and safe operation of electrical systems.
Copper
Aluminum
18 AWG
16 AWG
14 AWG
12 AWG
10 AWG
8 AWG
6 AWG
4 AWG
2 AWG
1 AWG
1/0 AWG
2/0 AWG
3/0 AWG
4/0 AWG
250 kcmil
300 kcmil
350 kcmil
400 kcmil
500 kcmil
Single Phase
Three Phase
Calculation Results:
Voltage Drop: 0.00 Volts
Percentage Voltage Drop: 0.00%
What is Voltage Drop?
Voltage drop refers to the reduction in electrical potential along the length of a conductor carrying current. As electricity flows through a wire, it encounters resistance, which causes some of the electrical energy to be converted into heat. This energy loss manifests as a drop in voltage from the source to the load.
Why is Voltage Drop Important?
Excessive voltage drop can lead to several problems:
- Reduced Efficiency: Appliances and motors may not operate at their full potential, consuming more energy to perform the same task.
- Equipment Damage: Motors can overheat and fail prematurely due to insufficient voltage. Electronic devices may malfunction or have a shortened lifespan.
- Dim Lighting: Lights may appear dim or flicker, especially at the end of long circuits.
- Safety Concerns: While less common, extreme voltage drop can sometimes indicate overloaded circuits, which can be a fire hazard.
The National Electrical Code (NEC) generally recommends a maximum voltage drop of 3% for feeders and 3% for branch circuits, for a total of 5% from the service point to the farthest outlet. This ensures optimal performance and longevity of electrical equipment.
Factors Affecting Voltage Drop
Several key factors influence the amount of voltage drop in a circuit:
- Current Load (Amperes): Higher current draws result in greater voltage drop.
- Wire Length (Feet): Longer wires have more resistance, leading to increased voltage drop.
- Wire Material: Different materials have different resistivity. Copper has lower resistivity than aluminum, meaning it offers less resistance for the same gauge and length.
- Wire Gauge (AWG/kcmil): Thicker wires (smaller AWG numbers, or larger kcmil numbers) have lower resistance and thus less voltage drop.
- Initial Voltage: The starting voltage of the circuit.
- Phase Type: Single-phase circuits have a different calculation constant than three-phase circuits.
How to Use This Calculator
To use the Voltage Drop Calculator, simply input the following information:
- Initial Voltage: The voltage supplied by your source (e.g., 120V, 240V, 480V).
- Current Load: The total current (in Amperes) that the circuit will carry. This is the sum of the current draw of all connected loads.
- One-Way Wire Length: The distance from the power source to the load, in feet. Remember this is one-way, not the total length of wire in a loop.
- Wire Material: Select whether your wire is Copper or Aluminum.
- Wire Gauge: Choose the American Wire Gauge (AWG) or kcmil size of your conductor.
- Phase Type: Indicate if your circuit is Single Phase (most residential) or Three Phase (common in industrial/commercial settings).
Click "Calculate Voltage Drop" to see the voltage drop in volts and as a percentage of the initial voltage, along with a recommendation based on common NEC guidelines.
Example Calculation
Let's say you have a 120V single-phase circuit running 15 amps over 100 feet using 12 AWG copper wire:
- Initial Voltage: 120 Volts
- Current Load: 15 Amperes
- One-Way Wire Length: 100 Feet
- Wire Material: Copper
- Wire Gauge: 12 AWG
- Phase Type: Single Phase
Using the calculator, you would find a voltage drop of approximately 2.58 Volts, which is about 2.15%. This is well within the recommended 3% limit for a branch circuit.
Now, consider the same scenario but with 200 feet of 14 AWG aluminum wire:
- Initial Voltage: 120 Volts
- Current Load: 15 Amperes
- One-Way Wire Length: 200 Feet
- Wire Material: Aluminum
- Wire Gauge: 14 AWG
- Phase Type: Single Phase
The calculator would show a voltage drop of approximately 12.34 Volts, or about 10.28%. This is significantly higher than the recommended 3% and would likely cause performance issues and potential damage to connected equipment. In this case, a larger gauge wire (e.g., 8 AWG copper) or a shorter run would be necessary.