Power Calculator
Calculate electrical power in watts from volts and amps.
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How It Works
Calculates electrical power using P = V × I (Ohm Law). Power (watts) is the rate of energy use. Also: P = I²R = V²/R. A 100W bulb uses 100 joules per second.
Formula
P = V x IQuick Reference
Common calculations — results you can verify instantly.
120V, 10A
P = 120×10
1,200W
240V, 30A
P = 240×30
7,200W
100W bulb, 1hr
Energy = 0.1kWh
~$0.012 at $0.12/kWh
Tips & Shortcuts
Kilowatt-hour (kWh) = Power (kW) × Time (h). Your electricity bill is in kWh.
A 2,000W heater for 3 hours = 6 kWh. At $0.12/kWh = $0.72.
Energy efficient appliances are rated in watts (lower is better).
Common Mistakes
Confusing watts with watt-hours
Watts measure power (rate). Watt-hours measure energy (total). A 100W bulb for 10 hours = 1,000 Wh = 1 kWh.
Adding power ratings directly without checking voltage compatibility
Ensure all devices operate at the same voltage before summing power consumption.
Frequently Asked Questions
1.5 kW × 8 h × $0.12 = $1.44 per day.
Volts is electrical pressure. Watts = Volts × Amps. Watts measure power (work done per second).
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