Click here for more Electrical Calculators

You can also follow us on Facebook and Linkedin to receive daily updates.

It follows the international electrical codes and standards to determine the

• Correct service panel size, 
• Connected load and 
• Demand load for any building.

The calculator covers the following installation types:

• Residential (Home): Single and multi-family dwellings
• Commercial (Office): Office buildings, retail spaces and light industrial facilities

Calculator Input Parameters

Installation Type

Select the installation type based on the building classification. 

This determines the applicable calculation method and demand factors.

Building Parameters

Living / Working Area (sq ft)

Enter the total floor area of habitable (or) usable space. 

This value is utilized to calculate the general lighting & receptacle load per NEC 220.12.

Electrical System Type

Single Phase (1Ø)

It is typical for residential installations in North America. 

It uses 2 hot conductors and one neutral.

Three Phase (3Ø)

Standard for commercial and industrial facilities. 

More efficient power delivery for large loads. 

Current is calculated using

I = Total VA / (V x 1.732)

System Voltage

Select the voltage standard applicable to your region

Base Electrical Loads (NEC 220.52)

Base loads represent the minimum electrical capacity that is required by code for general lighting and receptacle circuits. 

They are used to calculated from the building area.

General Lighting Load

Formula: Lighting VA = Living Area (sq ft) x 3 VA

Small Appliance Circuits (NEC 220.52(A))

Each small appliance circuit in the kitchen and dining area is rated at 1500 VA. 

A minimum of 2 circuits is required by code for most residential kitchens.

• Formula: Small Appliance VA = Number of Circuits x 1500 VA
• Minimum circuits required: 2 (per NEC 210.11(C)(1))
• Applied at 100% demand factor

Laundry Circuits (NEC 220.52(B))

Each laundry circuit is rated at 1500 VA. Residential installations require at least one dedicated laundry circuit.

• Formula: Laundry VA = Number of Circuits x 1500 VA
• Minimum circuits required: 1 (per NEC 210.11(C)(2))
• Applied at 100% demand factor

Appliances & Equipment Reference

The following table lists all appliances that are available in the calculator with their rated wattage values. 

These are standard nameplate ratings used for load calculations.

Custom Equipment

The calculator accepts custom equipment entries. 

Enter the equipment name and rated wattage in watts (W). 

Use the nameplate rating (or) manufacturer specifications.

HVAC: Non Coincident Load Calculation

Cooling and heating systems do not operate simultaneously. 

The NEC and IEC standards allow engineers to utilize the larger of the 2 loads (AC or heating) rather than adding both together.

AC / Cooling Load

Enter the total wattage of all cooling equipment: central AC, split units, window units (or) refrigeration systems. Sum all cooling loads in watts.

Electric Heating Load

Enter the total wattage of all electric heating: resistance heating elements, heat pump heating mode (or) portable space heaters.

Non-Coincident Rule: HVAC Demand = MAX (AC Load, Heating Load). Only the larger value is included in the total demand calculation. This is permitted by NEC 220.60.

Calculation Method & Formulas

Total Connected Load

The connected load is the sum of all loads before demand factors are applied:

Connected VA = Lighting VA + Small Appliance VA + Laundry VA + Appliances VA + HVAC VA

Total Demand Load

The demand load applies code specified demand factors

Service Amperage Calculation

Single Phase: Amps = Total Demand VA / Voltage

Three Phase: Amps = Total Demand VA / (Voltage x 1.732)

The calculated amperage is then rounded up to the nearest standard breaker/service size:

15A, 20A, 30A, 40A, 50A, 60A, 70A, 80A, 100A, 125A, 150A, 175A, 200A, 225A, 250A, 300A, 400A

Calculator Output & Results

Load Breakdown

The detailed breakdown shows each load category separately.

• General Lighting & Circuits: demand-adjusted lighting load
• Small Appliance Circuits: kitchen and dining area loads
• Laundry Circuits: washing area loads
• Added Appliances: sum of all individually added equipment
• HVAC System: the larger of AC or heating load

Service Panel Recommendations

Based on the calculated service amperage, the tool recommends:

• Main Service Panel: the minimum rated main breaker for the installation
• Subpanel (if needed): sized at 50% of main service for secondary distributions

Standards & Code Compliance

This calculator is designed for compliance with the following international standards.

Solved Example

Residential 2000 sq.ft Home

Inputs

• Living Area: 2000 sq.ft
• System: Single Phase 240V (USA)
• Small Appliance Circuits: 2
• Laundry Circuits: 1
• Appliances: Electric Range (12000W), Water Heater (4500W), Clothes Dryer (4000W), Refrigerator (200W)
• AC Load: 3500W  
• Heating Load: 0W

Calculation

Result

Service Amps = 32750 VA / 240V = 136.5A

Recommended Service Panel = 150 Amps

Important Notes

• Always verify inputs against actual equipment nameplate ratings
• Future load growth of 20-25% is recommended as a safety margin
• Local utility requirements may impose additional constraints
• Motor loads require additional starting current calculations (NEC 430)
• For large commercial projects, hire a Professional Engineer (PE) for load studies.