I am new to this website - excuse any errors. My question: I.m remodeling & wiring my basement and looking for wattgage limitations on 15 & 20 amp ckt breakers.
AJD66

With regard to what? Lighting? Receptacles?
Actually in a residence there literally is no limit. We just use common sense when figuring circuit loads.

Mathematically speaking the limit on a 15 amp line is 1800 watts. The mathematical limit for a 20 amp line is 2400 Watts.

The formula for calculating the minimum no. of lighting circuits is:

3xSq. ft. (of the garage)/120 = Number of Watts (2) watts/15 or 20 (choose what lines you are working on = Min # of Circuits.

For example: 3x1200sqft.= 3600/120 = 30 30/15 = 2

With regard to what? Lighting? Receptacles?
Actually in a residence there literally is no limit. We just use common sense when figuring circuit loads.

I was laughing so hard when I read this, I fell on the floor:D

It's pretty much true!

Thanks Stan, you made my day! :)

I think the actual context of the question was missed.


looking for wattgage limitations on 15 & 20 amp ckt breakers.


With regard to what? Lighting? Receptacles?
Actually in a residence there literally is no limit. We just use common sense when figuring circuit loads.


I was laughing so hard when I read this, I fell on the floor

It's pretty much true!

Thanks Stan, you made my day!


While there is no limitation of Quantity of outlets on a general lighting branch circuit in a residence, there is still the amperage/wattage limitations of that circuit, being 1800 watts/15 amps for a 15 amp circuit, and 2400 watts/20 amps for a 20 amp circuit.

And since it can be reasonably assumed that any general purpose lighting circuit in a home can run fully loaded for 3 hours or more, each circuit needs to be derated down to 80 %, or 1440 watts/12 amps maximum for a 15 amp circuit, and 1920 watts/16 amps for a 20 amp circuit.

Just thought this should be cleared up for the poster asking the question.

Actually no. This is taken into account with the 3 watts sq/ft.
See NEC 220.14(J)

Like I said, we just use common sense in figuring circuit load.

Didn't we just come back to my original answer?