Electrical Panel Schedule Calculator

How It Works

An electrical panel schedule tracks every circuit in the panel: its breaker size, load, and which bus bar (phase) it connects to. Proper load balancing keeps the two legs of a split-phase panel roughly equal. NEC Article 220 provides demand factors that reduce the calculated load for sizing purposes, since not all loads run simultaneously.

The Formula

Variables

• Panel Rating — The main breaker size in amps -- determines maximum continuous load capacity
• Connected Load — Sum of all individual circuit loads -- usually exceeds panel rating due to demand diversity
• Demand Factor — NEC 220 multiplier that accounts for the fact that not all loads run simultaneously
• 80% Rule — NEC 210.20 -- continuous loads should not exceed 80% of the overcurrent device rating

Example

A 200A residential panel with 20 active circuits totaling 150A: Load = 150/200 = 75%. Available = 50A (12,000 VA at 240V). With 42 spaces total, 22 remain. Panel is in good shape with room for an EV charger (40-50A) and a few more circuits.

Tips

• Keep a panel schedule posted on the inside of the panel door -- it helps during emergencies and future work.
• Balance loads between the two legs (L1 and L2) of a split-phase panel to avoid neutral overloading.
• The 80% rule applies to continuous loads (3+ hours) -- intermittent loads like garbage disposals can use full breaker rating.
• Tandem (slimline) breakers can double circuit count in some panels -- check the panel listing for approved positions.
• Always leave 4-6 spare spaces for future circuits when planning a new panel installation.