Demand Loads for Single Family Dwelling per NFPA 70A

[bearthebuilder3000]

Hi Everyone,

I'm an architect / builder working on a new spec house prototype and I was hoping to get some guidance on how to determine the overall demand load for the electrical panel. I'm pretty well versed in FBC and navigating code in general, but I'm new to electrical design and NFPA 70A has been a bit challenging.

I've put together my panel schedule and figured out all of my connected loads , but I cant seem to figure out which demand factors to apply to which connected loads in order to determine the total demand load for the panel. I've linked a working copy of the plans and schedules. Any insight would be appreciated.

Linked Plan & Schedules - Please disregarding circuit callouts on plans. That was a first pass and has not been updated to match the linked panel schedule

Connected Loads

• Lighting: 1.25 KVA
• Receptacles: 9.42 KVA
  • Only includes 110V receptacles
• Motors: 0.90 KVA
  • (2) 50W exhaust fans (Not sure if this is miscategorized. I've sometimes seen it listed under lighting)
  • (1) 800W Garage Door Opener.
• AC: 1.3 KVA
  • AHU only
• Heating: 5.0 KVA
  • Supplemental heat kit only. Condensing unit omitted as non-coincidental.
• Kitchen: 16.05 KVA
  • Includes small appliance circuits plus all kitchen appliances.
    • Should kitchen appliances be included here or should they be included under receptacles?
• Other: 12.25 KVA
  • Includes water heater, dryer, washer, and smoke detectors
• Total Connected Load = 46,170 VA / 240V = 192.38 A
  • This is where I'm stuck. I've been reviewing NFPA 70A for the last two days but don't understand how to get from the total connected load to the demand load.

 

[Elect117]

To start, it is called NFPA 70 or the NEC. Calling it 70A is a little funny.

You would be referencing article 220 and can use either the standard method or optional method. The standard method starts at 220.40 and the optional method starts at 220.80.

When using the standard method, you move through each permissible reduction and apply it. For example, the lighting, your small appliance branch circuit and laundry circuit loads are allowed to be reduced based on table 220.42.

The optional method is much easier to calculate and typically results in a lower required value.

If you have a copy of the NEC or have NFPA link then you can use the examples in the annex to help.

 

[bearthebuilder3000]

Thank you for the quick response. Looking at the NFPA website, it shows NFPA 70 and NFPA 70A as separate volumes. I didn't realize that NFPA 70A was contained within NFPA 70. I actually calculated the demand load using both the standard and optional method (link to schedules included in the original post). But looking at samples from other EE's, the demand factors dont quite translate from the Feeder / Service load calculations to the panel demand load.

For example, in both standard and optional method, the lighting and general power is calculated at 3va per s.f. plus small appliance plus laundry. You then take a reduction on anything above the first 3 kva. But when your calculating lighting as continuous load, you have to apply a demand factor of 1.25 which is not listed in either 220.40 or 220.80. Looking at some other examples I see motor loads being calculated at 1.25 and kitchen loads taken at 0.65 but I cant find where thats coming from.

I guess I'm having a hard time decerning which demand factors apply to feeder sizing and which apply to panel load. I've got a lot to learn but Ill work my way through a few of the examples to see if I can further refine the question. In the meantime, if your able to take a look at the linked plans and schedules, maybe my mistake will stand right out to you. At the very least, you might get a good laugh out of it.

 

[suemarkp]

Residential lighting is usually not considered continuous. The largest motor is usually the air conditioning compressor or a garbage disposal. Name plate MCA on an AC compressor already includes the 125% factor. A garbage disposal may need 25% added. Many things that are cord and plug connected are not counted (e.g. TV's, computers, misc chargers) because they are included in the 3VA per square foot value. Typically, the things you count in the kitchen are built in range/ovens, built in microwaves, dishwasher, and garbage disposal. Anything on the counter that is a movable appliance is included in the 1500 VA kitchen small appliance circuits. Likewise, the clothes washer, and dryer if it is gas, are covered by the laundry small appliance circuit. An electric clothes dryer would be counted separately as are water heaters.

In the standard calculation, there is a 75% factor that can be applied to most fixed appliances if you have 4 or more of them. Electric ranges have their own demand factor value in the standard calculation. The 35% factor in the standard calculation only applies to the general lighting, small appliances circuits once you're above 3KVA. The other appliances just add on to that with no reduction except for the ones I listed previously.

In the optional calculation, once you are past 10 KVA, every appliance gets counted as 40% except for HVAC. HVAC has its own demand factors depending on type and number of separately controlled heating elements

I hear in 2026, the calculations may be quite different, so one you figure this out you'll be figuring it all out again. Car chargers are one item I would consider not applying any factors to even though the code seems to allow that now. That may also change in 2026.

 

[Elect117]

I think what you are getting hung up on is the differences between calculating branch circuit loading and feeder/service loading.

The idea for a branch circuit is to ensure continued safe operation of the device, equipment, etc. So you size the wire for the load and the breaker to protect the wire. In some unique and more advanced circumstances, like motors, you have a wider allowance for protection.

Feeder and Service loading allow for demand factors which is what we are talking about using.

So you would still size the branch circuit to the load and you would not apply a demand factor to it. It wouldn't make sense to have a bunch of lights and undersize the conductors feeding them. But what you can do, is say that nobody uses 100% of their homes connected load all the time. So how do we compensate for that at the service or feeder? We use the allowed demand factors. I remember hearing that they come up with the allowable demand factors by conducting studies.

I looked at your linked plans and panel schedules. You are close.

A branch circuit load that is considered to be continuous (on for 3hrs or more concurrently) should have a 125% multiplied by the load. Then the wire and branch circuit should cover that. That is section 210.19(A)(1)(a).

IF you are deciding on whether or not to purchase a copy of the NEC, I would suggest buying the handbook for the additional explanations or getting NFPA link which include the handbook version.

 

[bearthebuilder3000]

Residential lighting is usually not considered continuous. The largest motor is usually the air conditioning compressor or a garbage disposal. Name plate MCA on an AC compressor already includes the 125% factor. A garbage disposal may need 25% added. Many things that are cord and plug connected are not counted (e.g. TV's, computers, misc chargers) because they are included in the 3VA per square foot value. Typically, the things you count in the kitchen are built in range/ovens, built in microwaves, dishwasher, and garbage disposal. Anything on the counter that is a movable appliance is included in the 1500 VA kitchen small appliance circuits. Likewise, the clothes washer, and dryer if it is gas, are covered by the laundry small appliance circuit. An electric clothes dryer would be counted separately as are water heaters.

In the standard calculation, there is a 75% factor that can be applied to most fixed appliances if you have 4 or more of them. Electric ranges have their own demand factor value in the standard calculation. The 35% factor in the standard calculation only applies to the general lighting, small appliances circuits once you're above 3KVA. The other appliances just add on to that with no reduction except for the ones I listed previously.

In the optional calculation, once you are past 10 KVA, every appliance gets counted as 40% except for HVAC. HVAC has its own demand factors depending on type and number of separately controlled heating elements

I hear in 2026, the calculations may be quite different, so one you figure this out you'll be figuring it all out again. Car chargers are one item I would consider not applying any factors to even though the code seems to allow that now. That may also ch

Got it. Thank you for clarifying on the compressor motor. Also, regarding the laundry circuit required in 220.52, is that meant to be a dedicated 20a circuit for just the washing machine or can I also connect a convenience outlet within the laundry room? I am currently showing one 20a circuit for the washer and another for the convenience outlet.

Regarding the upcoming NEC changes, Florida is always a few releases behind. We probably wont have to worry about the 2026 edition until sometime in 2032.

I think what you are getting hung up on is the differences between calculating branch circuit loading and feeder/service loading.

The idea for a branch circuit is to ensure continued safe operation of the device, equipment, etc. So you size the wire for the load and the breaker to protect the wire. In some unique and more advanced circumstances, like motors, you have a wider allowance for protection.

Feeder and Service loading allow for demand factors which is what we are talking about using.

So you would still size the branch circuit to the load and you would not apply a demand factor to it. It wouldn't make sense to have a bunch of lights and undersize the conductors feeding them. But what you can do, is say that nobody uses 100% of their homes connected load all the time. So how do we compensate for that at the service or feeder? We use the allowed demand factors. I remember hearing that they come up with the allowable demand factors by conducting studies.

I looked at your linked plans and panel schedules. You are close.

A branch circuit load that is considered to be continuous (on for 3hrs or more concurrently) should have a 125% multiplied by the load. Then the wire and branch circuit should cover that. That is section 210.19(A)(1)(a).

IF you are deciding on whether or not to purchase a copy of the NEC, I would suggest buying the handbook for the additional explanations or getting NFPA link which include the handbook version.

You hit the nail on the head. I think part of the confusion is that I might not be referencing the best precedent. But, if I'm understanding correctly, the panel size would be based on the feeder / service loading not the connected load determined in the panel schedule. In this case, using the optional method, I came up with a total demand load of 122A (145A using standard method). Does that mean I could technically get away with a 125A or 150A panel even though the connected load comes to 185A?

I've noticed that most EC's I've worked with throw a 200A panel into pretty much any SFH. I never really questioned it, but its starting to seem like overkill on some of these smaller builds.

 

[jaggedben]

Does that mean I could technically get away with a 125A or 150A panel even though the connected load comes to 185A?

Yes, because it's very unlikely that it will all be used simultaneously. And even if a 125A breaker ran at 127A for 3 mins it probably wouldn't trip and everything would be fine.

I've noticed that most EC's I've worked with throw a 200A panel into pretty much any SFH. I never really questioned it, but its starting to seem like overkill on some of these smaller builds.

Yes from one point of view a lot of people's money has actually been wasted. Many houses don't need anywhere near 100A, let alone twice that. But the labor time to do careful load calcs probably would eat up a lot of the difference in material cost, and oversizing 90% of people's services is better for builders and ECs than having to redo 10% for whom standardizing on a smaller size would cause callbacks and complaints. And, these days, with electrification and EVs and such, it's certainly limiting to have only a 100A service. YMMV especially depending on where in the country.

 

[suemarkp]

The laundry circuit is for the laundry area and no where else. That is sort of ill defined, but it would cover the washer (and gas dryer) receptacle, and convenience receptacles for perhaps ironing and other things in the laundry area. When a laundry is in a garage or basement with no defining walls, where laundry stops and the other rooms begins is a gray area.

A 200A panel has historically been oversized for a residence. Even a large one, as square footage doesn't add that much of a requirement. It is when you have all electric heating, multiple kitchens, or some other big swingers in the load calc like a 50A car charger, an electric instant water heater, etc. that you need 200A or more.

 

[Elect117]

I personally prefer to oversize but will offer it either way.

If you installed a 225A panelboard with a 200A main breaker you have more space for solar on a load side connection or future EV charging. The cost in labor is negligible but the cost in material is higher.

Some people don't mind spending the extra couple thousand upfront for the extra room for growth. Depends on the customer.

 

[jaggedben]

...

Some people don't mind spending the extra couple thousand upfront for the extra room for growth. ...

Yeah and if they are spending a million on a remodel and redoing all the electrical anyway I generally don't pinch pennies for them when they won't notice the difference. I figure it's much better to give them something they will never complain about.

That said I will gladly do a load calc to avoid a whole scope of work that otherwise doesn't need to happen. Like to justify downsizing a main breaker instead of replacing a whole service for solar.

 

[jaggedben]

The laundry circuit is for the laundry area and no where else. That is sort of ill defined, but it would cover the washer (and gas dryer) receptacle, and convenience receptacles for perhaps ironing and other things in the laundry area. When a laundry is in a garage or basement with no defining walls, where laundry stops and the other rooms begins is a gray area. ...

Following the examples in the Annex it's really quite simple for most single family homes. Take the square footage from the plans for new construction, or google the address and take it from the real estate websites for an existing home. Multiple that by 3, so say its 6000VA for the average home. Then add 4500kVA (for SABCs and laundry). Then add 240V appliances. Being completely honest I just ignore any 110V appliances fixed in place or not. Meaning that if I'm looking at the OP's example I'd just be ignoring the fans, garage door opener, smoke detectors, and probably some of the kitchen stuff. I figure that since the 3VA/sq ft is way out of date for LED lighting nowadays I'm already covered for that stuff. Until someone calls me on it I'm just gonna keep doing in that way. The 240V appliances are what ultimately make any real difference.

 

[brycenesbitt]

Ah, load calculations.
First, save yourself some hassle and create a spreadsheet for that.
-
The NEC calculations are well known to leave a lot of "room for growth", or be "grossly oversized" depending on your perspective.
There's even a non-profit "Panel Optimization Work and Electrical Reassessments [POWER]" group trying to advocate for reform to the calculations in the current NEC cycle. The group's work is based on real measurements of 1000's of real homes.
--
Many electrical technologies are getting less intensive. For example heat pump dryers run off a 20A circuit.
LED lighting is nearly everywhere. And appliances are getting smarter about capacity and load shifting. Space heaters? Who needs 'em in a well built house. What are we left with that's new, towel warmers? Should we count Gaming rig PC's or laptops. The garage door opener? Give me a break: that will run for 60 seconds a few times a day: there's no reason to even mention it.
--
You should consider adding a line to your load calculation for EV charging, but you can list that at 0A if you provide space for load management.
And specify a "solar ready" panel, though even the big box ones now are by default.

Your kitchen range calculations need review as well: ranges are special in the NEC and complicated. This is because they run their nameplate rating only for short periods, then modulate back to maintain heat. The nameplate is kind of made up.
--
Many other nameplates are made up. Actually measure what these devices do and seeing 20% to 50% of the nameplate as a peak is not at all uncommon.

---
For new construction the cost of supersizing electrical is very small.
For existing construction this is a huge deal. Entire valid projects can be deep sixed by overly dumb load calculations.

 

[bearthebuilder3000]

Got it. Thank you for clarifying on the compressor motor. Also, regarding the laundry circuit required in 220.52, is that meant to be a dedicated 20a circuit for just the washing machine or can I also connect a convenience outlet within the laundry room? I am currently showing one 20a circuit for the washer and another for the convenience outlet.

Regarding the upcoming NEC changes, Florida is always a few releases behind. We probably wont have to worry about the 2026 edition until sometime in 2032.

You hit the nail on the head. I think part of the confusion is that I might not be referencing the best precedent. But, if I'm understanding correctly, the panel size would be based on the feeder / service loading not the connected load determined in the panel schedule. In this case, using the optional method, I came up with a total demand load of 122A (145A using standard method). Does that mean I could technically get away with a 125A or 150A panel even though the connected load comes to 185A?

I've noticed that most EC's I've worked with throw a 200A panel into pretty much any SFH. I never really questioned it, but its starting to seem like overkill on some of these smaller builds.

Ah, load calculations.
First, save yourself some hassle and create a spreadsheet for that.
-
The NEC calculations are well known to leave a lot of "room for growth", or be "grossly oversized" depending on your perspective.
There's even a non-profit "Panel Optimization Work and Electrical Reassessments [POWER]" group trying to advocate for reform to the calculations in the current NEC cycle. The group's work is based on real measurements of 1000's of real homes.
--
Many electrical technologies are getting less intensive. For example heat pump dryers run off a 20A circuit.
LED lighting is nearly everywhere. And appliances are getting smarter about capacity and load shifting. Space heaters? Who needs 'em in a well built house. What are we left with that's new, towel warmers? Should we count Gaming rig PC's or laptops. The garage door opener? Give me a break: that will run for 60 seconds a few times a day: there's no reason to even mention it.
--
You should consider adding a line to your load calculation for EV charging, but you can list that at 0A if you provide space for load management.
And specify a "solar ready" panel, though even the big box ones now are by default.

Your kitchen range calculations need review as well: ranges are special in the NEC and complicated. This is because they run their nameplate rating only for short periods, then modulate back to maintain heat. The nameplate is kind of made up.
--
Many other nameplates are made up. Actually measure what these devices do and seeing 20% to 50% of the nameplate as a peak is not at all uncommon.

---
For new construction the cost of supersizing electrical is very small.
For existing construction this is a huge deal. Entire valid projects can be deep sixed by overly dumb load calculations.

Got it. Big thanks to everyone for walking me through this. I really appreciate everyone's insight and experience.

 

[jaggedben]

... Then add 4500kVA (for SABCs and laundry). ...

Oops, that 'k' didn't belong in there.