NEC 220.83(A): The Existing Dwelling Load Calculation, Worked
NEC 220.83(A) is the National Electrical Code calculation for an existing home that is adding a load, like an EV charger, without adding new air conditioning or electric heat. You add 3 VA per square foot for lighting and receptacles, 1,500 VA for each small-appliance and laundry circuit, and the nameplate rating of fixed appliances, count the first 8,000 VA at 100% and the rest at 40%, then add the existing heating or cooling load and the new load. If the total, divided by 240 volts, is at or under the service rating, the existing service can carry it.
I'm Jason Walls, Kentucky-licensed electrician (KY license EE642643), IBEW Local 369. This is the method that fits most homeowners adding an EV charger, and it is the one ChargeRight's report runs when nothing else about the house is changing. Below: when it applies, each step, and two homes worked line by line.
What is NEC 220.83(A)?
NEC 220.83(A) is the load calculation for an existing home adding load without new air conditioning or electric heat: general loads with the first 8,000 VA at 100% and the rest at 40%, plus existing HVAC and the new load, compared to the service rating.
It answers one question: does the service already on the house have room for one more load. That is a different question from sizing a new service, which is what 220.82 is for.
NEC References:
- NEC 220.83
- NEC 220.83(A)
- Table 220.83(A)
- NEC 230.79
Last updated: October 2026
When 220.83(A) applies
- 220.83(A): the home exists, you are adding load (an EV charger, a hot tub), and no new air conditioning or electric space heating is going in.
- 220.83(B): same, but new air-conditioning or electric space-heating equipment is going in too.
- 220.82: you are sizing a new service or a whole dwelling from scratch.
The steps
- Lighting and general-use receptacles at 3 VA per square foot (220.83(A)(1)).
- 1,500 VA for each 20-amp small-appliance branch circuit and each laundry branch circuit (220.83(A)(2)).
- Nameplate rating of appliances fastened in place, permanently connected, or on a specific circuit; ranges, wall ovens and cooktops; dryers not on the laundry circuit; water heaters (220.83(A)(3)).
- Table 220.83(A): the first 8 kVA of that total at 100%, the remainder at 40%.
- Existing heating or cooling, the larger of the two, at 100%.
- The new load. ChargeRight adds an EV charger at 100% of its setting: amps x 240 V.
- Divide by 240 to get amps and compare to the service rating.
The pass/fail test is NEC 230.79: the service disconnect has to be rated at least the calculated load. At or under 100% of the rating passes. ChargeRight also marks 80% of the rating as an advisory comfort line; between 80% and 100% the service passes but is tight.
Worked example 1: a 200-amp home adding a 48-amp charger
2,000 sq ft, gas furnace, 3-ton central air, electric range, electric dryer, gas water heater, two kitchen circuits, one laundry circuit, nothing else new. Run through the ChargeRight engine:
| Line | VA |
|---|---|
| General lighting and receptacles: 2,000 sq ft x 3 VA220.83(A)(1) | 6,000 |
| Small-appliance circuits: 2 x 1,500 VA220.83(A)(2) | 3,000 |
| Laundry circuit: 1 x 1,500 VA220.83(A)(2) | 1,500 |
| Fixed appliances: electric range 8,000 + electric dryer 5,000220.83(A)(3) | 13,000 |
| Subtotal before demand factor | 23,500 |
| After demand factor: 8,000 + 40% x 15,500Table 220.83(A) | 14,200 |
| Existing cooling, 3-ton AC (engine estimate; gas heat) | 3,600 |
| New EV charger, 48 A x 240 V, at 100% | 11,520 |
| Total | 29,320 |
29,320 VA / 240 V = 122.17 A on a 200-amp service: 61.1% of the rating. That passes, with about 78 amps of headroom. The same inputs through 220.82 come to 127.17 A, higher because 220.82's first tier is 10,000 VA instead of 8,000; 220.83(A) governs here because the home exists and no new HVAC is going in.
Worked example 2: a 100-amp home adding a 48-amp charger
1,500 sq ft, gas furnace, 2.5-ton central air, electric range, electric dryer, gas water heater, two kitchen circuits, one laundry circuit:
| Line | VA |
|---|---|
| General lighting and receptacles: 1,500 sq ft x 3 VA220.83(A)(1) | 4,500 |
| Small-appliance circuits: 2 x 1,500 VA220.83(A)(2) | 3,000 |
| Laundry circuit: 1 x 1,500 VA220.83(A)(2) | 1,500 |
| Fixed appliances: electric range 8,000 + electric dryer 5,000220.83(A)(3) | 13,000 |
| Subtotal before demand factor | 22,000 |
| After demand factor: 8,000 + 40% x 14,000Table 220.83(A) | 13,600 |
| Existing cooling, 2.5-ton AC (engine estimate; gas heat) | 3,000 |
| New EV charger, 48 A x 240 V, at 100% | 11,520 |
| Total | 28,120 |
28,120 VA / 240 V = 117.17 A on a 100-amp service. That exceeds the rating, so the full 48-amp charger does not fit as the house stands. Before an upgrade, look at the charger setting, since only the last line changes:
| Charger setting (circuit) | Total | Result |
|---|---|---|
| 48 A (60 A) | 117.17 A | Exceeds |
| 40 A (50 A) | 109.17 A | Exceeds |
| 32 A (40 A) | 101.17 A | Exceeds |
| 24 A (30 A) | 93.17 A | Passes, tight |
At 24 amps the house passes the 230.79 test at 93% of the rating. NEC 625.42 lets an EVSE with restricted-access adjustable settings be counted at its adjusted setting, so that is a legitimate install, not a workaround. Whether 24 amps is enough charging is a driving question, and for many households it is. The Tesla-specific version of this check is in can my panel handle a Tesla Wall Connector.
Where the charger sits. ChargeRight adds the new charger at 100% of its setting, on top of the demand-factored total. A literal reading of 220.83(A)(3)a (appliances fastened in place or on a specific circuit) could put a hardwired charger inside the 40% pool, which would give a lower total. ChargeRight keeps the conservative placement, so if these examples are off, they are off toward telling you to check further.
How 220.83(A) differs from 220.82 and 220.83(B)
| Method | Used for | General load tier | HVAC |
|---|---|---|---|
| 220.83(A) | Existing home adding load, no new HVAC | First 8 kVA at 100%, rest at 40% | Existing, larger of heat or cool |
| 220.83(B) | Existing home adding load and new AC or electric heat | First 8 kVA of other loads at 100%, rest at 40% | Larger of AC or space heat at 100%, not both |
| 220.82 | New service or whole-dwelling sizing | First 10 kVA at 100%, rest at 40% | Per 220.82(C), with its own factors |
ChargeRight computes all of them and names the one that governs your house instead of defaulting to one. For more on the other two, see NEC 220.83 (A) and (B) explained and NEC 220.82 explained.
Which code edition this is
ChargeRight's engine implements NEC 2023, Section 220.83(A) and Table 220.83(A). The 220.83 demand factors and load list are the same in the 2017, 2020 and 2023 editions, so the math above does not change between them. Two 2023 wording points if you are citing it: lighting is "as determined by 220.42" (it was 220.12 in 2017), and the tables are formally numbered Table 220.83(A) and (B).
Adoption is up to each state, and cities can amend. Kentucky is on the 2023 NEC. In Indiana, confirm the adopted edition and any local amendments with your building department before you cite a section number to an inspector. The 2026 NEC reorganizes this section as 120.83, with different values; it is not yet adopted in most places.
State pages: Kentucky, Indiana, Florida, all states.
Run it on your house
The ChargeRight assessment runs 220.83(A) (or 220.83(B) or 220.82, when those are the ones that apply) on your home from panel photos and a short questionnaire, and shows every line. It is $49.99, one time, on evchargeright.com. The install itself is a job for a licensed electrician, with a permit and an inspection.
Questions about 220.83(A)
What is NEC 220.83(A)?
It is the part of NEC 220.83, "Existing Dwelling Unit," used when an existing home adds load without adding new air-conditioning or electric space-heating equipment. Lighting and receptacles at 3 VA per square foot, 1,500 VA per small-appliance and laundry circuit, and fixed appliances at nameplate are added up; the first 8,000 VA counts at 100% and the remainder at 40%.
When do I use 220.83(B) instead of 220.83(A)?
When new air conditioning or electric space heating is being installed along with the other new load. 220.83(B) counts the larger of the air conditioning or space heating at 100%, but not both, and puts all other loads through the same first-8,000-VA-at-100%, remainder-at-40% structure.
What is the difference between NEC 220.82 and 220.83?
NEC 220.82 calculates a dwelling's total load from scratch, with the first 10,000 VA at 100%; it is the method for new construction or a planned service change. NEC 220.83 calculates the load on an existing service that is taking additional load, with an 8,000 VA first tier. For an existing home adding an EV charger, 220.83 is the section written for the question.
Which NEC edition is this based on?
ChargeRight's engine implements NEC 2023, Section 220.83(A) and Table 220.83(A). The 220.83 demand factors and load list are the same in the 2017, 2020 and 2023 editions, so the math does not change between them, only the citations. States adopt editions on their own schedules: Kentucky is on the 2023 NEC; confirm Indiana's adopted edition and any local amendments with your building department.
Can a 100-amp service handle a 48-amp EV charger under 220.83(A)?
It depends on the house. In our 100-amp worked example with an electric range and dryer, a 48-amp charger calculates to 117.17 amps, which exceeds the rating; the same home at a 24-amp setting calculates to 93.17 amps and passes. A 100-amp home with gas cooking and drying has far more room.
Does 220.83(A) put the EV charger inside the 40% demand factor?
ChargeRight adds the new charger at 100% of its setting, on top of the demand-factored total, which is the conservative reading. A literal reading of 220.83(A)(3)a, appliances fastened in place or on a specific circuit, could put a hardwired charger inside the 40% pool and produce a lower number. ChargeRight keeps the conservative placement.
About the Author
Jason Walls
Licensed Electrician, IBEW Local 369, EVITP Certified. Jason built ChargeRight to give homeowners the same NEC load calculation licensed electricians use, before anyone quotes them a panel.