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Demand Load Calculator

Calculate residential service demand load per NEC Article 220: general lighting, appliances, HVAC, and service size.

About this calculator

This calculator applies NFPA 70's Article 220 Standard Calculation Method for a single-family dwelling's electrical service, the same method an electrician uses to size your main panel and service entrance conductors. It starts with general lighting at 3 VA per square foot (33 VA/m²) per NEC Table 220.12, adds two 1,500 VA small-appliance kitchen circuits (Article 210.11(C)(1) minimum) and a 1,500 VA laundry circuit, then applies the Article 220.42 demand factor to that subtotal: the first 3,000 VA counts at full value, and everything above it is derated to 35% — reflecting the reality that a house never runs every light and small appliance simultaneously. Fixed appliance loads (range, dryer, dishwasher, water heater) are derated to 75%, per NEC 220.53. For climate control, only the larger of air conditioning (100%) or electric heating (65%, per NEC 220.51) counts toward demand, since a home's central AC and central heat are never on together — Article 220.60. An EV charger is added at full nameplate value since Level 2 charging is a genuinely continuous, unlikely-to-diversify load.

The calculator reports both the Total Connected Load and the smaller Calculated Demand Load the code actually lets you size to. Total Connected Load is not a plain sum of every input: like the demand calculation, it counts only the larger of air conditioning or electric heating (rather than adding both together), on the reasoning that a home's central AC and central heat never run at once, so the raw nameplate total already reflects that mutual-exclusivity rule before any demand factors are layered on top. From there the Calculated Demand Load applies the lighting, appliance, and heating derating described above, and the result is divided by 240V and rounded up to the nearest standard breaker size (100A through 1000A) for the Minimum Service Size. Keep in mind this is the simplified dwelling-unit method — commercial and multi-family services use different demand tables entirely.

Inputs

sq ft

NEC Table 220.12: 3 VA/ft² for dwellings; demand factors per NEC Table 220.42

circuits

NEC 210.11(C)(1): minimum 2 kitchen small appliance circuits × 1,500 VA = 3,000 VA

circuits
VA
VA
VA

NEC 220.51: electric heating at 65% demand; NEC 220.60: count only larger of AC vs. heat

VA

Results

Calculated Demand Load

24,785 VA

Minimum Service Size

125 A

General Lighting Load6,600 VA
Small Appliance + Laundry4,500 VA
Total Connected Load32,300 VA

Figures current as of 2026. Source: National Fire Protection Association, NFPA 70, National Electrical Code (NEC), 2026 Edition, Article 220

How to Use This Calculator
  1. Enter the Floor Area in m² — NEC Article 220 assigns 33 VA/m² for general lighting in dwellings.
  2. Enter the number of Kitchen Small Appliance Circuits (NEC minimum is 2) and Laundry Circuits (minimum 1).
  3. Enter the total Fixed Appliance Loads in VA — sum nameplate VA for range, dryer, dishwasher, and water heater.
  4. Enter the Air Conditioning Load and Electric Heating Load in VA — NEC uses the larger of the two with a 65% demand factor on heating.
  5. Enter the EV Charger Load in VA if applicable (e.g., Level 2 at 240V × 30A = 7,200 VA) — counted at 100% demand.
  6. Read the Calculated Demand Load in VA and the Minimum Service Size in amperes to select the correct service entrance equipment.

How the result changes with EV Charger Load

EV Charger LoadCalculated Demand LoadMinimum Service Size
3,60021,185 VA100 A
5,40022,985 VA100 A
10,80028,385 VA125 A
18,00035,585 VA150 A

What each input means

Floor Area
Total floor area of the dwelling in square meters. NEC Table 220.12 requires 3 VA/ft² (33 VA/m²) for general lighting in dwelling units. First 3,000 VA at 100%, remainder at 35% demand factor.
Kitchen Small Appliance Circuits
Number of 20A kitchen small appliance circuits. NEC 210.11(C)(1) requires a minimum of two 20A small appliance branch circuits for kitchen receptacles. Each 20A circuit = 1,500 VA.
Laundry Circuits
Number of laundry circuits (at least 1 required per NEC 210.11).
Fixed Appliance Loads
Total nameplate VA of fixed appliances (range, dryer, dishwasher, water heater, etc.).
Air Conditioning Load
Total air conditioning nameplate VA. Used if larger than heating.
Electric Heating Load
Total electric heating nameplate VA. NEC 220.51 permits 65% demand factor for electric heating loads. Only the larger of AC or heating is counted in demand calculations per NEC 220.60.
EV Charger Load
EV charger nameplate VA (e.g., Level 2 at 240V × 30A = 7200 VA). 100% demand.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Floor Area = 200, Kitchen Small Appliance Circuits = 2, Laundry Circuits = 1, Fixed Appliance Loads = 9000 = 7 input(s) provided
  2. Calculate Calculated Demand Load
    Calculated Demand Load
    24785 = 24785
  3. Calculate Minimum Service Size
    Minimum Service Size
    125 = 125
  4. Calculate General Lighting Load
    General Lighting Load
    6600 = 6600
  5. Calculate Small Appliance + Laundry
    4500 = 4500

Figures and sources

Engine last updated . Checked against 2 independently-derived tests — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.

Frequently Asked Questions

Why is my Total Connected Load higher than the Calculated Demand Load?

Total Connected Load is the raw nameplate sum of everything you entered (with only the AC-vs-heating exclusivity rule applied), while Calculated Demand Load applies NEC's demand factors on top of that: general lighting above 3,000 VA is derated to 35%, fixed appliances to 75%, and only the larger of AC or heating counts. The demand figure is almost always smaller because it reflects that a house never runs every circuit at full nameplate power simultaneously — and it's the number NEC actually lets you size the service to.

Why does adding a second laundry circuit or extra kitchen circuit change the demand load by more than 1,500 VA?

Kitchen and laundry VA get added into the same subtotal as general lighting before the 220.42 demand factor is applied. If that subtotal is already above 3,000 VA, every additional VA you add — including from a new circuit — is derated to 35%, so 1,500 VA of new circuit only adds 525 VA to the demand lighting figure, not the full 1,500.

Why did my EV charger load count at full value instead of being reduced like the other loads?

The calculator applies 100% demand to the EV Charger Load input rather than a derating factor, because Level 2 charging is treated as a continuous, non-diversifying load — unlike lighting or appliances, it doesn't cycle on and off in a way that lets you assume it's never running at full draw. That's also why a large charger can push the Minimum Service Size up disproportionately compared to other loads of the same VA.

My heating load is much larger than my AC load — why isn't it just added at 65%?

NEC 220.60 says only the larger of AC or heating counts toward demand, and heating gets a further 65% demand factor applied on top of that comparison (via heatingLoad × 0.65). So if heating's derated value is still larger than the AC load, that derated heating figure is what enters the demand total — the AC load is dropped entirely, not added alongside it.

What NEC sections is this demand calculation actually based on?

Every demand factor here traces to a specific subsection of NFPA 70 Article 220: 220.42 sets the tiered demand factor for general lighting (100% of the first 3,000 VA, 35% above it), 220.52 sets the 1,500 VA figure for each kitchen small-appliance and laundry circuit, 220.53 sets the 75% demand factor for fixed appliances, and 220.60 is the rule that only the larger of air-conditioning or heating load counts toward the total.

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