New to this? Plain-English guide

Connected Load vs Demand Load — connected load is everything added up as if it all ran at once; demand load is the realistic peak, since you never run every appliance simultaneously. Panels are sized on demand.

Demand Factor — the fraction of connected load expected to actually run at the same time, from electrical-code tables. It's why a house full of outlets doesn't need a huge service.

Service Size (Amps) — the capacity of your main breaker and meter connection. Common homes use 100-200A.

W/sq ft — a code shortcut: general lighting and outlets are estimated at ~3 watts per square foot of floor area.

System Configuration

Voltage

Phase

Service Type

Power Factor

Units

Load Schedule

General Lighting

Floor Area (sq ft)

W/sq ft

Lighting Load: 0 W

Small Appliance Circuits

Number of Circuits

Each

Small Appliance Load: 3,000 W

Laundry Circuit (1,500W)

Fixed Appliances

Appliance

Watts

Qty

Total

Fixed Appliance Total: 0 W

HVAC & Heating

Air Conditioning (W)

Heating (W)

Larger load will be used per NEC 220.60

Motors

Motor

Qty

Watts

Motor Load: 0 W (demand: 0 W)

Custom Loads

Name

Watts

Qty

Demand

Custom Load Total: 0 W

Wire Sizing & Voltage Drop

Circuit Amps

Cable Material

Insulation Type

Conduit Type

Ambient Temp (°C)

Current-Carrying Conductors

One-Way Length (ft)

Voltage Drop Target

Project Management

Load Saved Project

Calculation Method: Load analysis per NEC Article 220. General lighting from Table 220.12, demand factors from Table 220.42, fixed appliance demand from 220.53, range demand from Table 220.55 Column C, dryer demand from 220.54, HVAC/heating largest per 220.60, motor loads per 430.24. Wire sizing per NEC Table 310.16 with temperature and conduit fill corrections.

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NEC Reference Guide

NEC Table 220.12 - General Lighting Loads

Occupancy

W/sq ft

Dwelling Units

Office Buildings

3.5

Retail Stores

1.5

Industrial

Warehouses

0.25

Hotels/Motels

NEC Table 220.42 - Lighting Demand Factors

Dwelling Units:
• First 3,000 VA at 100%
• Remainder at 35%

All Others (Hotels, Hospitals, etc.):
• First 12,500 VA at 100%
• Remainder at 50%

NEC Table 220.55 - Ranges (Column C)

Number

Demand (kW)

Key NEC Demand Factor Rules

• 220.52 - Small appliance & laundry: 1,500W each
• 220.53 - 4+ fixed appliances (excl. range/dryer/HVAC): 75% demand
• 220.54 - Dryer: max(nameplate, 5,000W)
• 220.55 - Range: use Table 220.55 Column C
• 220.60 - HVAC vs Heating: use larger, not both
• 430.24 - Motors: 125% of largest + 100% of rest

Wire Sizing - NEC Table 310.16

AWG

Cu 75°C

Al 75°C

20A

—

25A

20A

35A

30A

50A

40A

65A

50A

85A

65A

115A

90A

1/0

150A

120A

2/0

175A

135A

4/0

230A

180A

Caribbean Notes

• JPS (Jamaica): 110/220V, 50Hz standard supply
• Most Caribbean islands use 110/220V or 120/240V split phase
• Trinidad & Tobago: 115/230V, 60Hz
• Barbados: 115/200V, 50Hz
• Hurricane-rated installations should oversize service entrance
• Corrosion: prefer copper over aluminum in coastal environments

Disclaimer: This calculator provides estimates for preliminary electrical load analysis. Actual service sizing depends on site-specific conditions, local amendments to the NEC, utility requirements, and equipment specifications. Always have calculations verified by a licensed electrical engineer or contractor before installation.

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