Residential Main Electrical Panel
Sizing Calculator

Professional sizing tool for home electrical services. Calculate total demand load per NEC Article 220.82 for Harris and Montgomery counties.

NEC 220.82 · TDLR TECL 29665 · Licensed Master Electrician

Current Configuration

Existing Panel Rating

Panel Brand / Safety

Home Profile

Conditioned Square Footage 2,000 sq ft
5001,5003,0004,5006,000+

HVAC (NEC 220.82 largest load)

Central AC Unit Size 3 Tons
1 Ton2 Tons3 Tons4 Tons5 Tons

Number of AC Units

Heating Type

Dedicated Circuits & Appliances

Select items present or planned to be added to your home.

Kitchen & Laundry

Vehicle & Tech

Outdoor & Specialty

Target Panel Amperage

200A

200-amp main breaker panel

NEC Optional Calculation Method
60A → 200A Target Upgrade
Panel Utilization —

Calculated Load Amps

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HVAC Demand

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Hazardous Panel: Federal Pacific/Stab-Lok panels are fire risks. Immediate replacement recommended.
Hazardous Panel: Zinsco/Sylvania panels have documented terminal failure. Replacement standard.
Service Overload: Your calculated demand exceeds current panel rating. Potential fire hazard.
High Utilization: Panel is above 80% safe continuous load. Future additions require upgrade.
Recommended: 200A service is the standard for modern Texas homes.
Permit Required: All service upgrades in Montgomery/Harris County require master electrician permits.
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Calculations based on NEC 220.82. Official load calculations by a Master Electrician are required for all legal permit applications.

How to Calculate Main Panel Load

Calculating the load on an electrical panel is essential before upgrading your home. We use the NEC 220.82 Optional Calculation, which is the standard for existing single-family dwellings.

The "General Load" Rule

The first 10,000 Volt-Amps (VA) are counted at 100%. Anything above that is calculated at 40%. This accounts for the fact that you rarely run every single light and outlet in your house at the same time.

HVAC & Diversity

Under NEC 220.82, we only take the larger of the two: Heating or Cooling. Since you don't run the AC and the Heater simultaneously, the Code only requires us to size for the largest potential load. This "diversity factor" reflects real-world usage.