Panel Schedule Builder
A
Voltage
Circuits
Total Connected Load3,300 W
Phase A Load1,800 W
Phase B Load1,500 W
Load Imbalance18.2%
Panel Utilization6.9%
Circuit Count2
Warnings
- !Load imbalance of 18.2% exceeds recommended 10% maximum
Circuit Directory
| # | Description | Breaker | Poles | Phase | Load (W) |
|---|---|---|---|---|---|
| 1 | Kitchen | 20A | 1P | A | 1,800 |
| 2 | Living Room | 20A | 1P | B | 1,500 |
A panel schedule documents every circuit in a distribution panel and, just as importantly, shows whether the load is balanced across phases. This builder distributes each circuit's watts across its assigned phase legs, totals the per-phase load, computes the imbalance between the heaviest and lightest legs, and tracks panel utilization, flagging conditions that violate good practice.
Formula
Imbalance% = (Pmax − Pmin) / Pavg × 100
- Pmax
- Watts on the most heavily loaded phase leg
- Pmin
- Watts on the least loaded (non-zero) phase leg
- Pavg
- Average watts across the loaded phase legs
- Imbalance%
- Percent difference used to flag unbalanced panels (10% recommended maximum)
How it works
- Set the panel name, main breaker amps, and voltage system (120/240 single-phase or 120/208 three-phase), then add circuits with a description, breaker size, pole count, load in watts, and phase assignment (A, B, C, or a multi-phase pairing).
- Each circuit's watts are split across the legs it occupies: a single-phase circuit loads one leg, a two-phase pairing splits evenly across two legs, and a three-phase circuit divides across all three.
- The tool sums each phase, computes the imbalance percentage from the spread between legs, and reports panel utilization against capacity, raising warnings when imbalance exceeds 10%, utilization passes 80%, or a leg exceeds the main rating.
Worked example
A 200 A, 120/240 V panel with a 1440 W lighting circuit on A, a 1200 W receptacle circuit on B, a 4800 W two-pole AC circuit on AB, and a 1500 W kitchen circuit on A.
- Phase A: 1440 + (4800 ÷ 2) + 1500 = 1440 + 2400 + 1500 = 5340 W.
- Phase B: 1200 + (4800 ÷ 2) = 1200 + 2400 = 3600 W.
- Average of the two legs: (5340 + 3600) ÷ 2 = 4470 W.
- Imbalance: (5340 − 3600) ÷ 4470 × 100 ≈ 38.9%. Total connected load = 8940 W; utilization = 8940 ÷ (200 × 240) ≈ 18.6%.
Phase A 5340 W, Phase B 3600 W, imbalance ≈ 38.9% (exceeds the 10% guideline), utilization ≈ 18.6%.
Frequently asked questions
- Why does load balance between phases matter?
- An unbalanced panel overloads one leg while leaving another underused, causing higher neutral current, extra heating, and wasted capacity. Keeping the imbalance within about 10% improves efficiency, reduces voltage variation between legs, and makes full use of the panel rating.
- How is panel utilization calculated?
- Utilization is the total connected watts divided by the panel's capacity. For a 120/240 V panel the capacity is main amps × 240; for a 120/208 V three-phase panel it is main amps × 208 × √3. Staying under 80% leaves headroom for growth and continuous loads.
- What does a two-pole or three-pole assignment do to the load?
- A multi-pole breaker spans more than one phase leg, so its load is shared. This tool splits a two-pole (AB, BC, AC) load evenly across its two legs and a three-pole (ABC) load across all three, which is how balanced 240 V and three-phase loads should be accounted for.
- Does this replace a formal panel schedule on the drawings?
- It produces the same load-balancing analysis and circuit directory you would document, but the official construction record should follow your jurisdiction's format and be verified against the installed panel directory and breaker ratings.