panelbook

Panel schedules that check themselves.
Macro-free Excel panel schedules, generated from Python and tested before every release.

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panelbook builds an Excel workbook of electrical panel schedules. Engineers and techs fill in yellow input cells; everything else (phase loading, demand, line currents, cable sizes, checks) is calculated by ordinary Excel formulas. No macros, so it opens the same in desktop Excel, Excel online, on a Mac and in LibreOffice.

The printed schedule keeps the familiar company layout, ready to paste into AutoCAD.

What it does

• Schedules in the company layout: CKT#, description, trip, poles, breaker type, wire size, L-1/L-2/L-3 VA, totals, load classification with demand factors, MCA.
• 42- and 84-circuit sheets (Template and Template 84), 12 to 84 circuits.
• Demand by load class: constant, tiered (NEC 220.42/220.44), quantity (220.56) and largest-motor +25% (430.24), applied to each panel's totals including its sub-panels.
• Sub-panels: pick a panel in any slot; its load comes in per phase and rolls up. The Panels register and Topology tree show the whole distribution system.
• Exact line currents for 1-, 2- and 3-pole loads on every system. Panel current is the highest line.
• High-leg delta (120/240 and 115/230 V): selectable high-leg phase, 1-pole loads blocked on it, orange rows, NEC 110.15 / 408.3 marking note, 240.85 breaker warning.
• Transformer-fed sub-panels with voltage-mismatch checks.
• Cable and EGC selection from NEC 310.16 and 250.122 with ambient and bundling factors, termination limits, 240.4(D) and parallel sets. Per-circuit override.
• Checks on every circuit and panel: ERR = must fix, WARN = check, each with a suggested fix.
• Print tabs with real merged cells and fixed shading, ready for printing and AutoCAD.

Using it

Download Panel_Schedule_Tool.xlsx from the latest Release and start on its Read Me sheet. Copy Template (or Template 84) for each new panel and list it on the Panels sheet.

Status

v2.2.0. In use for review on a live project. See panelbook/CHANGELOG.md.

Next (v2.2):

Area	Change
Assurance	Source-cited tables, independent reference model, approved-panel tests, in-workbook self-test sheet
Products	Catalogue table of breaker lines actually specified; WARN when not in catalogue
Cables	Per-circuit ambient / conduit fill; voltage drop with upsizing
Loads	Design (spare-capacity) factor; existing load from metering (NEC 220.87); optional power factor

Building from source

Needs uv (or Python 3.10+ with pip) and LibreOffice (used headless to recalculate).

uv sync                                        # once: creates .venv with Python + dependencies
uv run python panelbook/make.py                # -> dist/Panel_Schedule_Tool.xlsx
uv run python panelbook/make.py --blank --out dist/panelbook_blank.xlsx
uv run pytest                                  # regression tests (30)
uv run python panelbook/tools/migrate.py old.xlsx new.xlsx   # carry a v2.0 project file forward

Without uv: pip install -r requirements.txt, then the same commands without uv run.

Never hand-edit the workbook: change panelbook/src/ and rebuild. Design notes and verification record: panelbook/docs/design-notes.md.

panelbook/
  src/        workbook generator (layout, lookups, panel sheet, register/topology, assembly)
  tests/      regression panels and checks
  tools/      migrate.py (carry older project workbooks forward)
  docs/       design notes, images
  make.py     build → recalc → finished workbook
shared/       LibreOffice recalc and cached-value injection

Releases

Tag panelbook-vX.Y.Z and push. GitHub Actions runs the tests, builds the workbook and attaches it to a Release with the changelog.

Responsibility

panelbook is a design aid. Results must be checked by a qualified engineer against the adopted code edition and manufacturer data; the engineer of record remains responsible for the design.

© 2026 Shankar Ramharack. All rights reserved.