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Voltage Calculator (Power & Current)

Calculate system voltage from power and current load. Includes reference validation for standard breaker sizes and line loss context.

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Category Electronics

Common Breaker Limits

  • 15A: Standard Residential Light/Outlet
  • 20A: Kitchen/Appliance Outlet
  • 30A: RV / Dryer / Small Welder
  • 50A: Electric Range / EV Charger
  • 100A: Main Service Entry
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About

When planning electrical systems, from solar battery banks to industrial machinery, understanding the relationship between Power (P) and Current (I) is essential. High current at low voltage results in significant transmission losses due to wire resistance. Conversely, higher voltages allow for thinner wires and more efficient power transfer.

This calculator determines the Voltage required to deliver a specific amount of Power at a given Current. It is designed to assist in system sizing, helping users verify if their proposed amperage matches standard voltage architectures (e.g., 12V, 24V, 48V, 120V).

power distribution amperage wattage electrical load battery systems

Formulas

The calculation is a direct rearrangement of the Power Law:

V = PI

Where:

  • V is Voltage (Volts).
  • P is Power (Watts).
  • I is Current (Amps).

Reference Data

System Voltage (V)Common Use CaseMax Power at 15A (P)Max Power at 20A (P)
5 VUSB / Logic75 W100 W
12 VAutomotive / Solar180 W240 W
24 VIndustrial / Trucks360 W480 W
48 VTelecom / EV Golf720 W960 W
120 VUS Mains1,800 W2,400 W
230 VEU Mains3,450 W4,600 W

Frequently Asked Questions

If you try to push 1000 Watts at 12 Volts, you need 83 Amps. This requires massive copper cables. If you push 1000 Watts at 120 Volts, you only need 8.3 Amps. Higher voltage reduces the current required for the same power, drastically reducing energy lost as heat in the wires.
Yes, for resistive loads. For inductive loads (motors) on AC, you must also account for the Power Factor (PF). This calculator assumes a Power Factor of 1.0.
Circuit breakers protect wires from melting. Standard household sizes are 15A and 20A. If your calculation results in a Current that exceeds the breaker rating, the breaker will trip.