1. What is kWh?

A kilowatt-hour (kWh) is a unit of energy representing the amount of electricity consumed over time. One kWh equals using 1,000 watts of power for one hour. It's the standard unit for measuring electricity usage on utility bills.

2. How the Calculation Works

The calculator uses the formula:

Where:

• \( V \) — Voltage (volts)
• \( I \) — Current (amps)
• \( PF \) — Power Factor (0 to 1)
• \( h \) — Time (hours)

For three-phase systems: Multiply the result by √3 (approximately 1.732)

3. Importance of Power Factor

Details: Power factor accounts for the phase difference between voltage and current in AC circuits. A PF of 1 means all power is effectively used (resistive loads), while lower PF indicates reactive power (inductive/capacitive loads).

4. Using the Calculator

Tips:

• For household appliances, voltage is typically 120V or 240V (North America)
• Most residential circuits are single-phase
• Industrial equipment often uses three-phase power
• Power factor is 1 for DC circuits and resistive AC loads

5. Frequently Asked Questions (FAQ)

Q1: Why multiply by √3 for three-phase?
A: Three-phase power has three voltage waveforms 120° apart, and √3 accounts for the phase-to-phase voltage relationships.

Q2: What's a typical power factor value?
A: Residential: 0.95-1.0; Industrial: 0.8-0.9; Motors at full load: ~0.85; Fluorescent lights: 0.5-0.9.

Q3: How do I find the current (amps) of a device?
A: Check nameplate rating or use a clamp meter. For appliances: I = P/V (power in watts divided by voltage).

Q4: Does this work for DC circuits?
A: Yes, use PF=1 and single-phase. The formula simplifies to kWh = (V × I × h) / 1000 for DC.

Q5: How accurate is this calculation?
A: It's theoretical. Actual consumption varies with voltage fluctuations, temperature, and load variations.