About Electrical Power Calculator

Solves for unknown electrical values using Ohm’s Law and the power equation. Enter any two of voltage, current, power, and resistance to calculate the rest. For AC circuits, an adjustable power factor splits results into real power (W), apparent power (VA), and reactive power (VAR). The Energy Cost tab estimates electricity costs from wattage and usage hours with monthly and yearly projections.

• DC formulas: P = V×I, P = I²×R, P = V²÷R, and Ohm’s Law (V = I×R)
• AC power triangle: real power (W), apparent power (VA), reactive power (VAR) with configurable power factor
• SVG power triangle diagram showing P, Q, S relationships and cos(φ)
• Energy cost tab: daily, monthly (30d), and yearly (365d) kWh and dollar projections
• 10 common appliance presets from LED bulb (9W) to air conditioner (3000W) for quick cost estimates
• Each result shows the formula used with substituted values for educational transparency

Frequently Asked Questions

What power factor should I use?

For DC circuits and resistive loads (heaters, incandescent bulbs), use 1.0. For motors and compressors, 0.80–0.85 is typical. For modern switch-mode power supplies (computers, LED drivers), 0.90–0.99 is common. When in doubt, 1.0 gives you the maximum (worst-case) power draw.

What’s the difference between this and the Electricity Cost Calculator?

This tool focuses on electrical engineering: solving circuits, understanding power factor, and seeing the formulas. The Electricity Cost Calculator is appliance-focused with a larger preset library and CO₂ emission estimates.