CALCULATORS / SOLAR AND RENEWABLE ENERGY

Off-grid solar and storage sizing calculator

Daily load and autonomy storage, supplied usable fraction.

solar-off-grid.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

This source describes an analytical model. Its quantities and checks are the view.

Scenario	dailyWh	storageWh	capacityAh
	480	1200	50
	384	960	40

All calculated quantities are listed with the inputs. Switch to Source to inspect the equations.

SCENARIOS / CALCULATED VALUESSAME SOURCE

Change an input to see the consequences.

capacity budget50.00 Ah✓ passes

BASELINE INPUTS

load20 Wduration24 hautonomyDays2 usable0.8 voltage24 V

CALCULATED

daily480 Wh

storage1200 Wh

capacity50 Ah

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# Off-grid solar and storage sizing
# Scope: Daily load and autonomy storage, supplied usable fraction.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

load = 20 W
duration = 24 h
autonomyDays = 2
usable = 0.8
voltage = 24 V

daily := load*duration [Wh]
storage := daily*autonomyDays/usable [Wh]
capacity := storage/voltage [Ah]

check capacity budget: capacity <= 60 Ah

scenario alternative: load = 16 W

Calculated from your source · not saved

Baseline · Baseline

capacity budget50.00 Ah ✓ passes

alternative · alternative

capacity budget40.00 Ah ✓ passes

Illustrative first-order example. Checks are editable requirements, not design standards. The broader topic may require additional equations, data, and validation.

Formula and units

This example uses the following equations. Input names and units match the editable source above.

daily: daily = load*duration [Wh]
storage: storage = daily*autonomyDays/usable [Wh]
capacity: capacity = storage/voltage [Ah]

Original worked example

These are the baseline values in the downloadable source. Edits above let you test your own values.

Given

load: 20 W
duration: 24 h
autonomy days: 2
usable: 0.8
voltage: 24 V

Calculated

daily: 480 Wh
storage: 1200 Wh
capacity: 50 Ah

Assumptions and limits

Daily load and autonomy storage, supplied usable fraction.

The requirement checks use the limits written in this example. Passing a check does not establish that the model covers every load, material behavior, or operating condition in a real design.

Download this .napkin example ↓

Take it further with your agent

Napkin keeps the inputs, equations, checks and assumptions together in one study. Your agent sets it up; you change the numbers.

Try with Claude ↗

codex 'Use Napkin (https://napkin.engineering/mcp, or the local Napkin plugin) to build a study: Off-grid solar and storage sizing. Inputs: daily load; autonomy days; solar resource; efficiency. Outputs: array rating; usable storage. Model scope: Location/weather inputs or explicitly selected irradiation assumptions. Read napkin_capabilities and the current snapshot. Ask me for the values that matter, label assumptions with units, author .napkin source, validate it and apply it with napkin_source using the current revision, then open the study. Add checks for the limits I supply. Keep unsupported analyses explicit.'

Claude needs the Napkin connector; Codex needs the Napkin plugin. Set up your agent ↗

The broader study

The topic brief below describes the broader scope. The worked example above states the particular calculation it implements.

Inputs: daily load, autonomy days, solar resource, efficiency
Outputs: array rating, usable storage
Modes: calculate, compare, sweep
Drawing: Energy and resource plots

EXECUTABLE WORKED EXAMPLE · FIRST-ORDER MODEL · CHECK THE SCOPE & ASSUMPTIONS