Home Electrical Panel Capacity Calculator
Estimate your electrical panel's total capacity, current load, and remaining headroom. Enter your panel's main breaker size and your major appliances/circuits to see if you have room for new loads.
Panel Information
Major Appliances & Circuits
Enter the amperage for each circuit breaker (leave 0 if not present).
Demand Factor Settings
NEC Article 220 allows demand factors — not all loads run simultaneously at full capacity.
Formulas Used
Panel Capacity (VA): Panel Amps × Service Voltage
Total Demand (Full Load): Sum of all circuit breaker amperage × voltage
NEC Demand Factor — General Lighting & Outlets (NEC 220.42):
First 3,000 VA @ 100% + Next 117,000 VA @ 35% + Remainder @ 25%
NEC Electric Range (NEC Table 220.55):
Single range ≤ 12 kW → 8 kW demand; >12 kW → 8 kW + 5% per kW over 12 kW
NEC Electric Dryer (NEC 220.54): 5,000W minimum or nameplate, whichever is greater
NEC Non-Coincident Loads (NEC 220.60): Use the larger of HVAC or electric heat, not both
NEC 80% Continuous Load Rule: Continuous loads ≤ 80% × panel amperage
Load Factor (%): (Total Demand Amps ÷ Panel Amps) × 100
Available Headroom: Panel Amps − Total Demand Amps
Assumptions & References
- Based on NEC (NFPA 70) Article 220 — Branch-Circuit, Feeder, and Service Load Calculations.
- Standard US residential split-phase service: 120/240V, 60 Hz.
- NEC 220.42 tiered demand factors apply to general lighting and receptacle circuits.
- NEC Table 220.55 used for electric range/oven demand (single household unit).
- NEC 220.54 used for electric dryer: 5,000W minimum demand for a single dryer.
- NEC 220.60 non-coincident load rule: only the larger of HVAC cooling or electric heating is counted.
- EV chargers are treated as continuous loads at 100% per NEC 625.42.
- The 80% rule (NEC 210.20) applies to continuous loads (operating 3+ hours).
- This calculator provides an estimate. Always consult a licensed electrician for actual panel assessments and upgrades.
- Local codes (e.g., California Title 24) may impose additional requirements beyond NEC minimums.
- Actual demand may vary based on usage patterns, climate, and specific appliance models.