# of outlets on a circuit

[Dennis Alwon]

One way of thinking of residential load is by "load density" not VA load per receptacle,
By intersecting the NEC 3 VA per ft2 general branch circuit load with the 6-foot spacing rule, we can determine the "Venn-style" load density of a circuit. A 15A, 120V circuit (1800 VA) serves a maximum of 600 SQFT; in no case can a 15A branch circuit serve an area larger than this. As room geometry changes, the minimum number of required outlets shifts, causing the "implied load" per outlet to fluctuate based on available "wall space" (defined as any wall segment ≥2 feet). You could in theory construct a 600 SQFT space served by one receptacle so the maximum loads for a 600 SQFT area look something like;

Configuration​	Outlets Required​	Implied VA per Outlet​
Standard Square room​	8​	225 VA​
Circular Room​	7​	257 VA​
3-Sides Glass sun room​	2​	900 VA​
Modern house all glass roll up doors?​	1​	1800 VA​

I used to use that concept but if you separate your lights from receptacles or include them in the sq.ft design then you may have 2 different numbers.

The sq.ft with just receptacle loads is not how the NEC states to calculate it in homes. If you did sq.ft with both lights and receptacles it would make more sense but as Rob pointed out it isn't in the code that it should be done that way.

 

[tortuga]

Interesting concept but nowhere in the NEC is it required to consider the room size when figuring out how many receptacles you want to put on a circuit.

Yeah agreed just my way of comparing the spacing requirements (210.52) with the residential branch circuit load density requirement (210.11 -> 220.10)
the max receptacles on a residential branch circuit is your user name @infinity
When wiring a dwelling the NEC regulates load density per SQFT, not # of receptacles.
The area size is a consideration the installer needs to be aware of:
The 15A 120V circuit in a dwelling can serve no more than 600 SQFT of area.
600 SQFT X 3VA = 1800VA.

 

[Dennis Alwon]

I just noticed that NC has an interpretation for the number of outlets (not just receptacles) on a branch circuit. It comes down to somewhat of @tortuga stated.

If you had a 3000 sq.ft home then you would calculate at 3 watts / sq.ft . This gives us 9000watts. A 15 amp circuit at 120v is 1800 watts so 9000/180 = 5 15 1mp lighting and receptacle circuits in addition to the required 20 amp circuits.

If you use 20 amp circuits then you have 2400 per circuit so 9000/2400 =3.75 or 4 branch cir. Of course these are minimum

Here is the amendment for NC

Question:How many receptacles are allowed on a branch circuit in a single family dwelling?

Answer:There is no specific limit to number of receptacles installed on each of the branch circuitsrequired by Section 210.11.The requirement for number of branch circuits in a dwelling is found in Section 210.11, whichreferences the power calculations required by Section 220.10. These calculations provide theminimum number of branch circuits for the dwelling. There is no requirement that each generallighting and receptacle outlet be considered in determining that number.The general lighting load (includes general purpose receptacles) considered for the dwelling isbased on the number of square feet of the dwelling multiplied by 3 volt-amperes (or watts in asingle-family dwelling) per square foot. This total is then evenly divided among branch circuits,meaning at least two.For general lighting and receptacle outlets, the total number of volt-amperes for any dwelling isdetermined by multiplying the dwelling area in square feet by 3 volt-amperes (watts) per squarefoot (Table 220.12). To determine the number of general lighting load branch- circuits, the loadin volt-amperes is then divided by the volt-amps per circuit.For 20-amp general lighting load circuitsdwelling area in sq ft X 3 volt-amperes per sq ft) / (20 amps X 120 volts per circuit) =number of circuits. Round up to the next whole number.For 15-amp general lighting load circuitsdwelling area in sq ft X 3 volt-amperes per sq ft) / (15 amps X 120 volts per circuit) =number of circuits. Round up to the next whole number.There are five additional 20-amp branch circuits required in 210.11(C); they are two for thesmall-appliances, one for the laundry receptacle outlet(s), one for the bathroom receptacleoutlet(s), and one for the garage if a garage exists.

 

[infinity]

Here is the amendment for NC

There wouldn't be a need for an amendment if the NEC already required the circuit to take into account the square footage of a room.

 

[tortuga]

Its easy to confuse residential service load calculations with residential branch circuit load calculations. The two numbers decouple in the 2026 NEC, for dwelling unit service load calcs its reduced to 2VA per SQFT, then since there is not as much load diversity on a branch circuit for dwelling branch circuit load calcs the load density remains at 3VA per SQ ft or 600 SQFT max per 1800VA circuit.

 

[Dennis Alwon]

There wouldn't be a need for an amendment if the NEC already required the circuit to take into account the square footage of a room.

I am sorry it isn't an amendment but an official interpretation of the section

Its easy to confuse residential service load calculations with residential branch circuit load calculations. The two numbers decouple in the 2026 NEC, for dwelling unit service load calcs its reduced to 2VA per SQFT, then since there is not as much load diversity on a branch circuit for dwelling branch circuit load calcs the load density remains at 3VA per SQ ft or 600 SQFT max per 1800VA circuit.

NC is still on the 2017 for one and two family dwellings

 

[tortuga]

Where dwelling branch circuit load calculations get interesting is when the 50% fixed appliance rule mixes in.
If an electrician hard-wires a continuous load say a 720 Watt bathroom towel bar heater into a 15A general-purpose circuit, we immediately loose the heaters continuous VA (900) from the 1800 VA total.
Now with only 900 VA left for "General Purpose" loads, that circuit can now only serve 300 ft2 instead of 600.

 

[infinity]

then since there is not as much load diversity on a branch circuit for dwelling branch circuit load calcs the load density remains at 3VA per SQ ft or 600 SQFT max per 1800VA circuit.

I'm not seeing where this wording exists in the NEC. Are you saying that a room 601 square feet is required to be served by more than one 15 amp circuit?

 

[tortuga]

I'm not seeing where this wording exists in the NEC. Are you saying that a room 601 square feet is required to be served by more than one 15 amp circuit?

In my 2023 book 220.10: says dwelling branch circuit loads shall be calculated in accordance with 220.41, which covers the 3VA per square foot.

 

[garbo]

Retired and here's my two cents: With expensive AFCI breakers required on most 120 circuits thought it would be cheaper to use #12 and have less circuits then if #14 was used for bedrooms & other areas. When NM was cheap I would place each bedroom on its own 20 amp circuit. It's a balancing act when you are giving out prices and competing with several other contractors. I was lucky in that I always had more work then I could handle them only did commercial work.