How to Design a Panel Schedule

SummaryAI-optimized for quick reference

Panel schedule design requires listing all circuits, calculating loads per NEC 220, applying demand factors, and sizing breakers and wires. Key NEC references: 220.12 (lighting 3 VA/sq ft for dwellings), 220.42 (demand factors: first 3000 VA at 100%, remainder at 35%), 210.20(A) (continuous loads at 125%), 240.6 (standard breaker sizes), 310.16 (wire ampacities). For residential: minimum two 20A small appliance circuits, one 20A laundry circuit. Typical 2,000 sq ft home: 200A main breaker, 30-42 circuit panel. Phase balance within 10% for 3-phase systems. Wire sizes: 14 AWG/15A, 12 AWG/20A, 10 AWG/30A, 8 AWG/40-50A, 6 AWG/55-60A at 60C copper per NEC 310.16.

Key Points

NEC 220.12 lighting loads: 3 VA/sq ft for dwellings, 3.5 VA/sq ft for offices—a 2,000 sq ft home has 6,000 VA base lighting load before demand factors
Demand factors reduce panel size: First 3,000 VA at 100%, remainder at 35% for dwellings (NEC 220.42)—a 10,000 VA connected load becomes 5,450 VA demand load
Continuous loads need 125%: Any load running 3+ hours (HVAC, EV chargers, commercial lighting) requires breaker sized at 125% of load current per NEC 210.20(A)
Phase balance within 10%: In 3-phase systems, keep phase loads balanced to prevent neutral overloading and transformer issues—spread large loads across phases
Standard breaker sizes (NEC 240.6): 15, 20, 25, 30, 35, 40, 50, 60, 70, 100A—always round UP to the next standard size
Wire sizing from NEC 310.16: 14 AWG for 15A, 12 AWG for 20A, 10 AWG for 30A, 8 AWG for 40A, 6 AWG for 55A at 60C copper

Quick AnswerHow do you design a panel schedule?

Design a panel schedule in 5 steps: (1) List all circuits with their VA loads, (2) Apply NEC demand factors to reduce calculated load, (3) Size branch circuit breakers at 125% of continuous loads, (4) Select wire sizes from NEC 310.16 based on ampacity, (5) Balance loads across phases within 10%. A typical 2,000 sq ft home needs a 200A panel with 30-42 circuits.

Key Takeaways

1**NEC 220.12 lighting loads**: 3 VA/sq ft for dwellings, 3.5 VA/sq ft for offices—a 2,000 sq ft home has 6,000 VA base lighting load before demand factors
2**Demand factors reduce panel size**: First 3,000 VA at 100%, remainder at 35% for dwellings (NEC 220.42)—a 10,000 VA connected load becomes 5,450 VA demand load
3**Continuous loads need 125%**: Any load running 3+ hours (HVAC, EV chargers, commercial lighting) requires breaker sized at 125% of load current per NEC 210.20(A)
4**Phase balance within 10%**: In 3-phase systems, keep phase loads balanced to prevent neutral overloading and transformer issues—spread large loads across phases
5**Standard breaker sizes (NEC 240.6)**: 15, 20, 25, 30, 35, 40, 50, 60, 70, 100A—always round UP to the next standard size
6**Wire sizing from NEC 310.16**: 14 AWG for 15A, 12 AWG for 20A, 10 AWG for 30A, 8 AWG for 40A, 6 AWG for 55A at 60C copper

What is a Panel Schedule?

A panel schedule is a detailed document that maps every circuit in an electrical panel. It's required by NEC 408.4 for proper panel identification. Panels must comply with UL 67 for panelboard standards and IEEE C2 (National Electrical Safety Code) for safe installations. The schedule serves as a roadmap for:

Electrical contractors during installation
Inspectors during code compliance review
Maintenance personnel for troubleshooting
Homeowners for understanding their electrical system

Column	Description	Example
Circuit #	Position in panel	1, 2, 3...
Description	Load name	"Kitchen Receptacles"
Breaker (A)	Overcurrent protection	20A
Poles	Single, double, or triple	1P, 2P, 3P
Voltage	Operating voltage	120V, 240V
Wire Size	Conductor gauge	12 AWG
VA/Watts	Load magnitude	1,800 VA

Typical Residential Load Distribution

How electrical loads are typically distributed in a home panel

20.0 kW

Total connected load

HVAC

35%(7,000W)

Water Heater

20%(4,000W)

Kitchen/Cooking

18%(3,600W)

Lighting

12%(2,400W)

Laundry

8%(1,600W)

Receptacles

7%(1,400W)

Largest load

HVAC (35%)

Service size for 20kW

200A typical

After demand factors

~12-15 kW

Step 1: Calculate General Lighting Load

NEC 220.12 specifies minimum lighting loads by occupancy type:

Occupancy Type	VA per sq ft	Example (2,000 sq ft)
Dwelling unit	3	6,000 VA
Office	3.5	7,000 VA
Bank	3.5	7,000 VA
School	3	6,000 VA
Store	3	6,000 VA
Warehouse	0.5	1,000 VA
Hospital	2	4,000 VA
Restaurant	2	4,000 VA

Lighting Load (VA)=Floor Area (sq ft)\times VA per sq ft\text{Lighting Load (VA)} = \text{Floor Area (sq ft)} \times \text{VA per sq ft}Lighting Load (VA)=Floor Area (sq ft)\times VA per sq ft

2,000 sq ft Home

Lighting load = 2,000 sq ft \times 3 VA/sq ft = 6,000 VA This represents the general lighting and receptacle load before adding specific appliances.

Step 2: Add Required Circuits

NEC mandates minimum circuits for dwelling units:

Required Circuit	Quantity	Breaker	VA Each	Total VA	NEC Reference
Small appliance (kitchen)	2 minimum	20A	1,500	3,000	210.11(C)(1)
Laundry	1 minimum	20A	1,500	1,500	210.11(C)(2)
Bathroom	1 minimum	20A	—	—	210.11(C)(3)

The two 20A small appliance circuits must serve ONLY kitchen, dining, and pantry areas. They cannot serve other rooms or fixed appliances like dishwashers.

Step 3: Apply Demand Factors

Not all loads operate simultaneously. NEC 220.42 provides demand factors to calculate realistic panel loading:

NEC Demand Factors

Load reduction factors for residential service calculations (NEC 220)

100% = Full load

Lower % = More reduction

20 kW connected load

→ ~12-14 kW demand

HVAC + Electric Heat

Count larger only

Savings from factors

25-40% reduction

Dwelling Unit Demand Factors

Portion of Load	Demand Factor
First 3,000 VA	100%
Remainder	35%

Demand Load=3000+(Total−3000)\times0.35\text{Demand Load} = 3000 + (\text{Total} - 3000) \times 0.35Demand Load=3000+(Total−3000)\times0.35

10,500 VA Connected Load

Connected load = 6,000 VA (lighting) + 3,000 VA (small appliance) + 1,500 VA (laundry) = 10,500 VA Demand load = 3,000 + (10,500 - 3,000) \times 0.35 = 3,000 + 2,625 = 5,625 VA This 46% reduction shows why demand calculations matter for panel sizing.

Step 4: Add Major Appliances

After the demand-factored general load, add specific equipment:

Electric Range (NEC 220.55)

Number of Ranges	Demand Load
1	8,000 VA
2	11,000 VA
3	14,000 VA
4	17,000 VA
5	20,000 VA

For ranges over 12 kW, add 5% for each kW over 12 kW

Electric Dryer (NEC 220.54)

Number of Dryers	Demand Factor
1-4	100%
5	80%
6	70%
7	65%
8	60%

Minimum demand: 5,000 VA per dryer

HVAC (NEC 220.60)

For noncoincident loads (heating OR cooling):

Use only the LARGER of heating or cooling load
Do NOT add both—they don't run simultaneously
Consider power factor for motor loads

Heat pumps with backup electric heat require both the compressor load AND backup heater load if they can operate simultaneously.

Step 5: Size the Main Breaker

Service Current (A)=Total Demand Load (VA)Voltage\text{Service Current (A)} = \frac{\text{Total Demand Load (VA)}}{\text{Voltage}}Service Current (A)=VoltageTotal Demand Load (VA)

For 240V single-phase residential service:

Total Demand	Calculated Current	Main Breaker
Under 12,000 VA	Under 50A	60A or 100A
12,000-20,000 VA	50-83A	100A
20,000-30,000 VA	83-125A	125A or 150A
30,000-48,000 VA	125-200A	200A
Over 48,000 VA	Over 200A	225A or 400A

Complete Residential Load Calculation

Load Category VA General lighting (2,000 sq ft \times 3) 6,000 Small appliance (2 \times 1,500) 3,000 Laundry 1,500 Subtotal before demand 10,500 After demand factors 5,625 Range (NEC 220.55) 8,000 Dryer (5,000 \times 100%) 5,000 Air conditioner 6,000 Water heater 4,500 Total Demand 29,125 VA Service current 29,125 \div 240 = 121A Main breaker 150A or 200A

Load Category	VA
General lighting (2,000 sq ft × 3)	6,000
Small appliance (2 × 1,500)	3,000
Laundry	1,500
Subtotal before demand	10,500
After demand factors	5,625
Range (NEC 220.55)	8,000
Dryer (5,000 × 100%)	5,000
Air conditioner	6,000
Water heater	4,500
Total Demand	29,125 VA
Service current	29,125 ÷ 240 = 121A
Main breaker	150A or 200A

Step 6: Size Branch Circuit Breakers

Wire Ampacity by Gauge (NEC 310.16)

Current-carrying capacity for copper conductors at different temperatures

60°C insulation (TW)

75°C insulation (THWN)

Standard breaker size

Most common residential

#12 AWG (20A breaker)

200A service requires

#4/0 AWG minimum

THWN advantage

+15-20% ampacity

The 125% Rule for Continuous Loads

Per NEC 210.20(A), breakers serving continuous loads (3+ hours operation) must be sized at 125%. Breakers must meet UL 489 standards for molded-case circuit breakers. The load calculation formula:

Breaker Size\geq Load Current\times1.25\text{Breaker Size} \geq \text{Load Current} \times 1.25Breaker Size\geq Load Current\times1.25

Continuous Load	Load Current	× 1.25	Breaker Size
Commercial lighting	16A	20A	20A
EV charger (32A)	32A	40A	40A
EV charger (40A)	40A	50A	50A
Pool pump	12A	15A	15A
Water heater	18.75A	23.4A	25A or 30A

Standard Breaker Sizes (NEC 240.6)

15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, 200A...

Always round UP to the next standard size.

Step 7: Select Wire Sizes

NEC Table 310.16 provides conductor ampacities. For detailed wire selection methods, see our cable sizing guide. Wire selection must also account for voltage drop on longer runs:

Copper Wire Ampacity at Different Temperature Ratings

Wire Size (AWG)	60°C	75°C	90°C	Typical Use
14	15A	20A	25A	15A circuits (lighting)
12	20A	25A	30A	20A circuits (receptacles)
10	30A	35A	40A	30A circuits (dryer)
8	40A	50A	55A	40-50A circuits (range)
6	55A	65A	75A	60A circuits (HVAC)
4	70A	85A	95A	70-80A circuits
3	85A	100A	115A	100A circuits
2	95A	115A	130A	Sub-panels
1	110A	130A	145A	Large sub-panels
1/0	125A	150A	170A	150A service
2/0	145A	175A	195A	175A service
3/0	165A	200A	225A	200A service
4/0	195A	230A	260A	200A+ service

60°C column: Most residential devices with standard terminals
75°C column: When both conductor AND terminations are rated 75°C
90°C column: Used for derating calculations only (not termination ampacity)

Step 8: Balance Phases (3-Phase Systems)

Phase Balancing Impact

How load distribution affects neutral current and system efficiency

Phase A

Phase B

Phase C

Goal: Keep imbalance

<10% of largest phase

Neutral overload risk

Above 30% imbalance

NEC 220.61

70% demand on neutral

For 3-phase panels, distribute loads to keep phases within 10% of each other:

Phase Assignment Rules

Load Type	Phase Assignment
Single-pole 120V	Alternates A-B-C-A-B-C
Double-pole 240V	Spans two phases (A-B, B-C, or C-A)
Triple-pole 3-phase	All three phases

Balancing Strategy

List all loads by phase assignment
Sum each phase separately
Calculate imbalance: (Max - Min) / Average
Target: Under 10% imbalance
Adjust: Move single-phase loads between phases

3-Phase Panel Balancing

Before balancing: Phase A: 25,000 VA Phase B: 18,000 VA Phase C: 20,000 VA Imbalance: (25,000 - 18,000) / 21,000 = 33% (too high!) After moving 3,500 VA from A to B: Phase A: 21,500 VA Phase B: 21,500 VA Phase C: 20,000 VA Imbalance: (21,500 - 20,000) / 21,000 = 7% (acceptable)

Safety and Code Compliance

Panel design must follow NFPA 70 (National Electrical Code) and NFPA 70E for workplace electrical safety. Key compliance points:

Safety Requirement	NEC Reference	Description
Working clearance	110.26	Min 3 ft depth, 30 in width in front of panel
Panel height	408.37	Overcurrent devices max 6 ft 7 in above floor
Circuit directory	408.4	Each circuit must be legibly identified
Arc-fault protection	210.12	AFCI required for bedrooms, living areas
Ground-fault protection	210.8	GFCI required for bathrooms, kitchens, outdoors

Common Panel Configurations

Residential Panels

Home Size	Typical Panel	Main Breaker	Circuits
Under 1,500 sq ft	100A, 20-space	100A	16-20
1,500-2,500 sq ft	200A, 30-space	200A	24-30
2,500-4,000 sq ft	200A, 42-space	200A	32-42
Over 4,000 sq ft	200A+, 42+ space	200A+	40+

Commercial Panels

Application	Typical Panel	Voltage	Phases
Small office	100-225A	120/208V	3-phase
Retail store	225-400A	120/208V	3-phase
Restaurant	400-600A	120/208V	3-phase
Industrial	600-1200A	277/480V	3-phase

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NEC 2023 compliant panel schedule builder with automatic load calculations

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How to Design a Panel Schedule: Complete NEC 2023 Guide

Table of Contents

Key Takeaways

What is a Panel Schedule?

Step 1: Calculate General Lighting Load

Step 2: Add Required Circuits

Step 3: Apply Demand Factors

Dwelling Unit Demand Factors

Step 4: Add Major Appliances

Electric Range (NEC 220.55)

Electric Dryer (NEC 220.54)

HVAC (NEC 220.60)

Step 5: Size the Main Breaker

Step 6: Size Branch Circuit Breakers

The 125% Rule for Continuous Loads

Standard Breaker Sizes (NEC 240.6)

Step 7: Select Wire Sizes

Copper Wire Ampacity at Different Temperature Ratings

Step 8: Balance Phases (3-Phase Systems)

Phase Assignment Rules

Balancing Strategy

Safety and Code Compliance

Common Panel Configurations

Residential Panels

Commercial Panels

Try the Calculator

Frequently Asked Questions

Frequently Asked Questions

How to Design a Panel Schedule: Complete NEC 2023 Guide

Table of Contents

Key Takeaways

What is a Panel Schedule?

Step 1: Calculate General Lighting Load

Step 2: Add Required Circuits

Step 3: Apply Demand Factors

Dwelling Unit Demand Factors

Step 4: Add Major Appliances

Electric Range (NEC 220.55)

Electric Dryer (NEC 220.54)

HVAC (NEC 220.60)

Step 5: Size the Main Breaker

Step 6: Size Branch Circuit Breakers

The 125% Rule for Continuous Loads

Standard Breaker Sizes (NEC 240.6)

Step 7: Select Wire Sizes

Copper Wire Ampacity at Different Temperature Ratings

Step 8: Balance Phases (3-Phase Systems)

Phase Assignment Rules

Balancing Strategy

Safety and Code Compliance

Common Panel Configurations

Residential Panels

Commercial Panels

Try the Calculator

Frequently Asked Questions

01What is a panel schedule and why is it important?

02How do you calculate electrical panel load?

03What size wire do I need for different breaker sizes?

04What is the 125% rule for continuous loads?

05How do you balance loads on a 3-phase panel?

06What circuits are required in a residential panel?

Frequently Asked Questions

01What is a panel schedule and why is it important?

02How do you calculate electrical panel load?

03What size wire do I need for different breaker sizes?

04What is the difference between connected load and demand load?

05How do you balance loads on a 3-phase panel?

06What circuits are required in a residential panel?

07What is the 125% rule for continuous loads?