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What is Electrical Load Calculator (Amps & Watts)?
The Electrical Load Calculator converts Wattage into Amperage to ensure your home circuits are not overloaded. Electrical safety codes typically mandate that continuous loads (running for 3+ hours) should not exceed 80% of the circuit breaker's rating. This tool helps homeowners and DIYers size their circuits correctly for appliances, lights, and heaters.
How it Works
The calculation uses Ohm's Law variants for power: Amps = Watts / Volts.
For example, on a standard 120V US circuit, a 1500W heater draws 12.5 Amps (1500 / 120). The tool then compares this total load against common breaker sizes (15A, 20A, 30A) and applies the 80% safety factor to warn of potential overloads.
Step-by-Step Guide
- Identify Voltage: 120V for standard US outlets, 240V for heavy appliances/Europe.
- Sum Wattage: Add up the power rating of all devices on the circuit.
- Calculate Amps: Divide Total Watts by Volts.
- Check Breaker: Ensure Amps < (Breaker Rating × 0.8).
Example
Input: 2000 Watts @ 120V
Result: 16.6 Amps (Requires 20A+ Circuit)
FAQ
What is the 80% rule?
For continuous loads (3+ hours), you should only use 80% of a breaker's capacity. E.g., 12A on a 15A breaker.
Watts vs Amps vs Volts?
Think of water: Volts = Pressure, Amps = Flow Rate, Watts = Total Water Power.
How much can a 15A circuit handle?
Max 1800W peak, or 1440W continuous at 120V.
Does startup surge matter?
Yes, motors (AC, Fridges) spike 3x current on startup. Leave headroom.
Wire gauge?
15A needs 14 AWG wire; 20A needs 12 AWG wire. Never use smaller wire on larger breakers.
Conclusion
Overloaded circuits are a fire hazard. If your calculated load exceeds the safe limit, you must move devices to another circuit or install a new dedicated line. Never replace a breaker with a larger one without upgrading the wire gauge (e.g., 14 AWG to 12 AWG).