Free tool
Will this appliance overload the circuit?
Enter what the appliance draws and which breaker protects the circuit. You get
the current, how much of the breaker it uses, and whether it stays inside the rule for loads
that run for hours.
0% of the breaker
Enter a load
Volts, amps, watts and ohms
Fill in any two boxes and the other two
follow. Clear a box to start over.
Enter two values.
The rule behind the result. A load that runs for three hours or
more is a continuous load. The branch circuit and its breaker have to be sized at 125 percent
of it, which is the same as saying the load may not exceed 80 percent of the breaker. On a
20 amp circuit that is 16 amps. NEC 210.19 and 210.20.
Watch the rest of the circuit. A breaker protects everything on
it, not just the one appliance. Lights, a fridge and a few outlets in the same room are often
on the same circuit, so use the field for the other load if you know it.
This is not a load calculation. To know whether the whole house or the
service is big enough you need a full calculation under NEC article 220, not this page.