Electrical Panel Size Calculator

Use this calculator to estimate the minimum required amperage for your home's electrical panel based on common loads, following a simplified version of the National Electrical Code (NEC) Optional Method for dwelling units. This tool helps you understand the electrical demands of your property.

Dwelling Square Footage (sq ft): Enter the total heated living area of your home.

Fixed Appliance Loads (Nameplate Rating in VA)

Enter the nameplate rating (Volt-Amperes) for each electric appliance. If not applicable, enter 0.

Electric Range (VA): Typical: 8,000 – 15,000 VA

Electric Dryer (VA): Typical: 4,500 – 6,000 VA

Electric Water Heater (VA): Typical: 3,500 – 5,500 VA

Dishwasher (VA): Typical: 1,000 – 1,500 VA

Garbage Disposal (VA): Typical: 700 – 1,200 VA

Built-in Microwave (VA): Typical: 1,000 – 2,000 VA

Other Fixed Appliances (Sum of VA): Sum of nameplate ratings for other fixed appliances (e.g., well pump, central vacuum, attic fan, etc.).

Largest Heating or AC Unit (VA): Enter the nameplate rating of the single largest heating or air conditioning unit. Do not sum both.

System Voltage (V): Typical residential voltage is 240V.

Understanding Your Home's Electrical Panel

The electrical panel, often called a breaker box or service panel, is the heart of your home's electrical system. It safely distributes electricity from the utility company to all the circuits and outlets in your house. Sizing your electrical panel correctly is crucial for safety, efficiency, and to ensure you have enough power for all your appliances and future needs.

Why Panel Sizing Matters

Safety: An undersized panel can lead to frequently tripped breakers, overheating wires, and even fire hazards. An oversized panel isn't inherently dangerous but can be an unnecessary expense.
Functionality: With an appropriately sized panel, all your appliances will receive the power they need to operate correctly without overloading the system.
Future Expansion: Modern homes often require more power than older ones due to an increase in electronic devices and large appliances. A properly sized panel can accommodate future additions like electric vehicle chargers, solar panels, or new kitchen appliances.
Code Compliance: Electrical work, including panel upgrades, must comply with the National Electrical Code (NEC) to ensure safety and pass inspections.

How the Calculator Works (Simplified NEC Optional Method)

This calculator uses a simplified approach based on the National Electrical Code (NEC) Optional Method (Article 220.82) for dwelling units. This method provides a straightforward way to determine the minimum service size required for a home.

The calculation generally involves these steps:

General Lighting & Receptacle Load: This is calculated based on your home's square footage (typically 3 Volt-Amperes per square foot). Additionally, fixed loads for small appliance branch circuits (two circuits at 1500 VA each) and a laundry circuit (1500 VA) are added.
Demand Factor for General Loads: The NEC applies a demand factor to these general loads. The first 10,000 VA are taken at 100%, and any remaining VA above 10,000 is taken at 40%. This acknowledges that not all general loads will be used simultaneously.
Fixed Appliance Loads: The nameplate ratings of all other fixed appliances (electric range, dryer, water heater, dishwasher, disposal, microwave, etc.) are summed. A demand factor of 75% is then applied to this total sum. This accounts for the fact that these appliances are also not typically all running at their maximum capacity at the same time.
Largest Heating or Air Conditioning Load: The full nameplate rating (100% demand factor) of the single largest heating or air conditioning unit is added. Only the largest of the two is considered, as they are generally not operated simultaneously.
Total Demand Load: All the calculated demand loads (general, fixed appliances, and largest heating/AC) are summed to get the total Volt-Ampere (VA) demand.
Amperage Calculation: The total VA demand is then divided by the system voltage (typically 240V for residential services) to determine the minimum required amperage.
Recommended Panel Size: The calculated amperage is rounded up to the next standard panel size (e.g., 100A, 125A, 150A, 200A, 225A, 400A).

Important Considerations

Consult an Electrician: This calculator provides an estimate for informational purposes only. Always consult a qualified, licensed electrician for an accurate assessment and professional installation. They can account for local codes, specific appliance requirements, and any unique aspects of your home's electrical system.
Future Needs: When planning an upgrade, it's often wise to consider future electrical needs. If you anticipate adding an EV charger, a hot tub, or significant new appliances, you might want to size slightly above the minimum calculated requirement.
Local Codes: Electrical codes can vary by jurisdiction. Your electrician will ensure compliance with all local regulations.