Electrical Load Calculator

Size a residential electrical service per NEC 2023 Article 220.82 — the Optional Method for one-family dwellings. Enter square footage and major appliances; get a recommended service size (100 / 150 / 200 / 400 A).

Dwelling info

ft²
Finished space — general lighting at 3 VA/ft² (NEC 220.12).

General load circuits

Min 2 per NEC 210.11(C)(1). 1,500 VA each.
Min 1 per NEC 210.11(C)(2). 1,500 VA each.
Min 1 per NEC 210.11(C)(3). 1,500 VA each.

Fixed appliances (nameplate VA)

VA
0 if gas. Typical 8–16 kVA.
VA
0 if gas. Min 5,000 VA per NEC 220.54.
VA
0 if gas. Typical 4–5 kVA.
VA
VA
VA
VA
0 if shared with small-appliance circuit.
VA
Sum any extras: built-in oven, instant hot water, etc.

HVAC (use the larger of cooling or heating)

VA
Typical: 3-ton ≈ 7 kVA, 4-ton ≈ 9 kVA, 5-ton ≈ 11 kVA.
VA
0 if gas heat. Electric strip 10–20 kVA typical.

Special loads

VA
40 A × 240 V = 9,600 VA. 48 A = 11,520 VA. Continuous load (×1.25).
VA
Sum pump + heater + lights if present.

Service size — NEC 220.82

Recommended service size

— A

Total demand

— VA

Calculated current

— A

With 25 % safety margin

— A

Standard service sizes: 100, 125, 150, 175, 200, 225, 320, 400 A. The recommendation rounds up to the next standard size after applying a 25 % safety / continuous-load margin.

Informational only. The final service determination must be made by a licensed electrician and comply with local code. Some AHJs (Authority Having Jurisdiction) require the Standard Method (NEC 220.40–44) rather than the Optional Method, or impose stricter minimums. Older Federal Pacific Stab-Lok and Zinsco panels should be replaced regardless of load — they are documented safety hazards.

The NEC 220.82 Optional Method

NEC Article 220 governs how electrical loads are summed and converted into a required service size. For one-family dwellings, NEC 220.82 (“Optional Calculation”) is the most common method — it produces realistic, slightly smaller services than the Standard Method, by recognising that not all loads run simultaneously.

general_load = 3 VA/ft² × sqft + 1,500 VA × (small_appl + laundry + bath) + Σ fixed_appliance_VA
demand_general = first 10,000 VA × 100 % + remainder × 40 %
total = demand_general + max(AC, heat) + EV + pool
service = ⌈ (total / voltage) × 1.25 ⌉ → next standard size

Why the 40 % demand factor

NEC recognises that the homeowner does not run the range, dryer, water heater, dishwasher and microwave all at the same time. The first 10,000 VA of general load is taken at full nameplate; the remainder is reduced to 40 % under 220.82(B). HVAC is held at 100 % because cooling load is sustained on hot days.

Continuous loads and the 1.25 margin

NEC 210.19 requires that any circuit serving a load running 3 hours or longer be sized at 125 % of the load. EV chargers are the classic example. The 25 % margin on the final service current is a conservative blanket application of this principle.

Worked example — 2,000 ft² home with full electric kitchen + AC + EV

Line itemVADemand factorDemand VA
General lighting (2,000 × 3)6,000
Small-appliance (2 × 1,500)3,000
Laundry (1 × 1,500)1,500
Bathroom (1 × 1,500)1,500
Range, dryer, WH, DW, disposal, microwave24,900
General subtotal36,900
First 10,000 VA10,000100 %10,000
Remainder (26,900 VA)26,90040 %10,760
AC (3-ton)7,000100 %7,000
EV charger (40 A × 240 V)9,600100 %9,600
TOTAL DEMAND37,360 VA
Current @ 240 V155.7 A
× 1.25 margin194.6 A
Recommended service200 A

Frequently asked questions

What size electrical service does a 2,000 sq ft house need?
A modern 2,000 ft² home with electric range, dryer, water heater, central AC and an EV charger typically calculates to about 195 A under NEC 220.82, which rounds up to a 200 A service. With gas heat/water/range and no EV, the same house often fits a 150 A service.
Is the NEC 220.82 Optional Method always allowed?
It is allowed only for one-family dwellings. Two-family and multi-family use 220.84. Commercial uses 220.40 series. Some local AHJs also require the Standard Method (220.40-44) even on single-family — check before sizing.
Do I need 200 A service for an EV charger?
Not always. A 40 A Level 2 charger adds 9,600 VA (12,000 VA with the 1.25 continuous-load multiplier). On a 100 A service running close to capacity, you would need to upgrade to 150 A or 200 A. On a 200 A service with light loads, the EV charger fits without upgrade.
What is the difference between Optional and Standard methods?
The Standard Method (NEC 220.40-44) applies demand factors line-by-line — different factors for lighting, small appliance, range, dryer, etc. The Optional Method (220.82) lumps general load together and applies a single 100/40 % step. Optional typically produces a smaller service size; Standard is more conservative.
Are 100 A services still allowed for new construction?
Technically yes if the load calculation supports it, but in practice most new construction installs 200 A as the default — it costs only $100-300 more than 100 A and accommodates future EVs, heat pumps and additions without an upgrade later. Some jurisdictions effectively require 200 A minimum.
What is a 1.25 continuous-load multiplier?
NEC 210.19 requires conductors and overcurrent devices serving continuous loads (3+ hours of operation) to be sized at 125 % of the load. The calculator applies this once to the final service current as a safety margin, which approximates the per-circuit application for the major continuous loads (lighting, EV chargers).
Does NEC 220.82 apply to my house?
Yes if you have a one-family detached dwelling (single home, not duplex, townhouse with party walls, or apartment). For multi-family, use NEC 220.84. The calculator is configured for the single-family case.