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Enter 0 for gas range
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NEC 220.60 counts larger of Heat vs A/C
Water heater, dishwasher, disposal total

Residential Service Load & Panel Calculator

Compute single-family residential electrical service demand (VA), continuous line amperes, and minimum service entrance disconnect rating per NEC 2023 Article 220 Standard Method.

⚡ NEC 2023 Code Basis & Electrical Safety Disclaimer

Based on NEC 2023 Article 220 Part III Standard Method (same math as 2020 & 2017). Standard-method informational estimate for planning — electrical service upgrades must comply with local code editions and be performed/verified by a licensed electrician. Not a substitute for engineered design or an AHJ ruling.

🏠 Residential Service Entrance Schematic
Service Entrance SchematicDiagram showing utility overhead/underground feed, electric meter socket, main service disconnect panel, and branch circuits.

Service Sizing Calculation Results

Minimum Service Panel Rating
100 A Service
NEC 230.79(C) 100A Floor
Calculated Line Current
75.4 A
Amperes @ 240V 1-Phase
Total Service Demand Load
18,100 VA
18.1 kW Total Demand
General Demand (Table 220.45)
5,100 VA
9,000 VA Gross Lighting & SA

Worked Example: 1,500 sq ft Dwelling Service Load Calculation

Step-by-step NEC Article 220 Standard Method calculation:

  • Step 1 (General Lighting Load): 1,500 sq ft × 3 VA/sq ft = 4,500 VA (NEC 220.41).
  • Step 2 (Small Appliance & Laundry): 2 Small Appliance circuits (3,000 VA) + 1 Laundry circuit (1,500 VA) = 4,500 VA (NEC 220.52).
  • Step 3 (Gross General Load): 4,500 + 4,500 = 9,000 VA.
  • Step 4 (Apply Table 220.45 Demand): First 3,000 VA @ 100% (3,000 VA) + remaining 6,000 VA @ 35% (2,100 VA) = 5,100 VA Demand.
  • Step 5 (Electric Range Demand): 12 kW range $\rightarrow$ Column C Table 220.55 demand = 8,000 VA.
  • Step 6 (Electric Dryer Demand): 5 kW dryer $\rightarrow$ NEC 220.54 min demand = 5,000 VA.
  • Step 7 (Total Service Load): 5,100 + 8,000 + 5,000 = 18,100 VA Total.
  • Step 8 (Service Amperes): 18,100 VA / 240V = 75.4 Amperes.
  • Step 9 (Minimum Disconnect Floor): Sized for 80 A breaker, but under NEC 230.79(C), single-family dwelling minimum service rating floor is 100 Amperes.

Engineering Code & Reference Citations

  • NFPA 70 / NEC Article 220 Part III: Feeder and Service Load Calculation Methods. nfpa.org
  • NFPA 70 / NEC Table 220.45: Lighting Load Demand Factors (renumbered from 220.42). nfpa.org
  • NFPA 70 / NEC Table 220.55 & Section 230.79(C): Demand Factors for Household Electric Ranges & Rating of Service Disconnecting Means. nfpa.org

Frequently Asked Questions (FAQ)

What is the calculated service load for a 1,500 sq ft house with 12 kW range and 5 kW dryer?

Under the NEC Article 220 standard calculation method: General lighting (4,500 VA) + 2 small appliance circuits (3,000 VA) + laundry (1,500 VA) = 9,000 VA gross. Applying Table 220.45 demand (first 3,000 VA @ 100% + remaining 6,000 VA @ 35%) gives 5,100 VA demand. Adding 8,000 VA range demand (Table 220.55 Col. C) and 5,000 VA dryer demand (220.54) equals 18,100 total VA. At 240V, current is 75.4 Amperes. Under NEC 230.79(C), the minimum service disconnect floor rating is 100 Amperes.

What is the minimum service disconnect rating for a single-family dwelling?

Under NEC 230.79(C), for a single-family dwelling, the service disconnecting means shall have a rating of not less than 100 Amperes, 3-wire.

How is general lighting load calculated per square foot in the NEC?

Under NEC 220.41 (220.12 in earlier editions), general lighting load for a dwelling unit is calculated at 3 Volt-Amperes (VA) per square foot of living area, excluding open porches, garages, or unused/unfinshed basements.

How many small-appliance and laundry branch circuits are required by the NEC?

Under NEC 210.11(C)(1) and (2), a dwelling unit requires a minimum of two 20-Ampere small-appliance branch circuits (calculated at 1,500 VA each) and at least one 20-Ampere laundry branch circuit (calculated at 1,500 VA).

How is the demand factor applied to general lighting and small-appliance loads?

Under NEC Table 220.45 (Table 220.42 in 2020/2017), the first 3,000 VA of combined general lighting, small-appliance, and laundry load is calculated at 100%; the portion between 3,001 VA and 120,000 VA is calculated at 35%; and any portion over 120,000 VA is calculated at 25%.

How is an electric range demand calculated under NEC Table 220.55?

Under Column C of NEC Table 220.55, one household electric range rated up to 12 kW has a maximum demand of 8 kW (8,000 VA). For ranges rated over 12 kW, add 5% to 8 kW for each additional kW (or major fraction) over 12 kW.

How is an electric clothes dryer sized in an Article 220 load calculation?

Under NEC 220.54, the load for an electric clothes dryer is calculated at 5,000 VA or the nameplate rating (whichever is larger) at 100% demand factor for 1 to 4 dryers.

How are heating and air conditioning loads handled under NEC 220.60?

Under NEC 220.60 (noncoincident loads), where it is unlikely that two powers will be used simultaneously (such as heating and A/C), only the larger of the two noncoincident loads is included at 100% demand.

When does a 200 Amp service panel become necessary instead of a 100 Amp panel?

When the calculated service load exceeds 100 Amperes (24,000 VA at 240V) — typical for homes over 2,000 sq ft with electric heat, central A/C, EV chargers, or multiple heavy appliances — a 200 Amp service panel is required.

What demand factor applies to 4 or more fastened-in-place appliances?

Under NEC 220.53, a demand factor of 75% applies to the total nameplate rating of four or more appliances fastened in place (such as water heater, dishwasher, garbage disposal, trash compactor), excluding electric ranges, clothes dryers, space heating, or A/C.

What is the optional calculation method under NEC 220.82?

NEC 220.82 permits an optional calculation for a single-family dwelling where general load (100% of first 10 kVA + 40% of remainder) is combined with 100% of A/C or heating load. This calculator uses the standard method under Part III.

Are NEC Article 220 dwelling calculation rules identical across 2017, 2020, and 2023?

Yes. The mathematical demand factors and percentages are identical across NEC 2017, 2020, and 2023. Note that the 2023 edition renumbered section 220.12 to 220.41 and Table 220.42 to 220.45.