Off-Grid Solar System Size Calculator
Build a first-pass off-grid solar package from daily kWh, sun hours, system losses, panel watts, battery capacity, voltage, running watts, and surge watts.
Enter system values
Build a first-pass off-grid solar package: panels, battery storage, controller amps, and inverter class.
Results update locally in your browser. CalcShelf does not save your entries or add them to links.
Solar planning sanity check
Use these rows to check assumptions before buying panels, batteries, inverter, controller, or cable.
Educational estimate only. Verify electrical code, permits, equipment manuals, fuse/breaker sizing, and qualified installation requirements before using results in a real system.
What this means
For 8 kWh/day, start around 6 panels, 4 battery units, a 70 A controller, and a 3500 W inverter.
| Component | Size |
|---|---|
| Panels | 6 × 400 W |
| Battery | 4 × 5.12 kWh |
| Controller | 70 A class |
| Inverter | 3500 W continuous |
- Size
- 6 × 400 W
- Size
- 4 × 5.12 kWh
- Size
- 70 A class
- Size
- 3500 W continuous
Copy / print
Copy or print this local-only worksheet for your own notes, installer questions, or parts list.
Watch-outs
- This is a planning estimate, not a stamped design.
- Winter sun and shading can dominate off-grid sizing.
- Inverter, controller, battery, and wiring specs must all match.
Safety boundary
This is a sizing planner, not a stamped electrical design. Treat these outputs as planning estimates, not installation instructions.
Displayed numbers are rounded to 2 decimal places where helpful.
Use the Off-Grid Solar System Size Calculator for the right job
Use this when you want one combined off-grid sizing worksheet before drilling into each component calculator.
Good for
- Cabin solar package planning
- Remote shed or workshop estimates
- Backup-power system rough sizing
How to use it
- Enter daily kWh, peak sun hours, and losses.
- Set battery autonomy and battery module capacity.
- Review panel count, battery count, controller amps, and inverter recommendation.
What changes the result
- Daily kWh
- Peak sun hours
- System losses
- Autonomy days
- Battery usable kWh
- Peak running and surge watts
Next calculators to check
Solar Load Calculator
Refine the daily kWh input.
Solar Battery Bank Size Calculator
Refine storage and autonomy.
Solar Charge Controller Size Calculator
Check the controller separately.
FAQ
How do I size an off-grid solar system?
Start with daily kWh, size panels from sun hours and losses, size batteries from autonomy days and usable depth, then size inverter and controller from load and array limits.
Why does off-grid solar need more margin than grid-tied solar?
Off-grid systems must handle cloudy periods, seasonal sun changes, battery limits, and load growth without utility backup, so conservative assumptions matter.
Can I use this as a final off-grid design?
No. Use it as a planning estimate before buying parts, then verify the design against equipment manuals, electrical code, fusing, conductor ratings, permits, and qualified installation advice.
Safety and accuracy notes
Solar and battery systems can involve high DC current, fire risk, permit requirements, electrical code, roof loading, wind loading, temperature derating, fusing, disconnects, and manufacturer limits. Use this as an educational planning estimate only, then verify real designs with qualified sources and equipment manuals.
Use the Off-Grid Solar System Size Calculator without guessing what to do next
- Start with the example values to see what the main result looks like.
- Replace the example values with the best numbers you have right now; rough estimates are fine for a first pass.
- Change one input at a time so you can see which assumption actually moves the answer.
What the result means
The result is a planning number for one part of a solar system: load, panels, strings, wire, battery, inverter, controller, mounting, backup, or payback.
How to use it
Use it to compare scenarios before buying hardware, then cross-check the adjacent calculators so one component is not sized in isolation.
What can change it
Solar estimates can move quickly with sun hours, shading, temperature, battery limits, voltage drop, surge loads, roof constraints, utility rules, and code requirements.
Good for
Plan a solar or backup-power system before buying equipment.
Check this next
Try Solar Load Calculator, Solar Battery Bank Size Calculator, Solar Panel Count Calculator to cross-check the same decision from another angle.
Best habit
Run a conservative case and an optimistic case. The gap between them is often more useful than a single answer.
Common uses
- Plan a solar or backup-power system before buying equipment.
- Check one sizing layer with local-only browser math.
- Pair with adjacent solar calculators for a full system sanity check.
Common questions
Is the Off-Grid Solar System Size Calculator private?
CalcShelf calculators run without an account. Your entries stay in the calculator while you work; CalcShelf does not save them or place your numbers in shareable links.
How accurate is the Off-Grid Solar System Size Calculator?
It is a solar planning worksheet. Sun hours, shading, derating, temperature, fusing, wire ratings, battery limits, permits, and equipment manuals can change the final design.
What should I check after using the Off-Grid Solar System Size Calculator?
Verify electrical code, fusing, wire ampacity, voltage drop, battery and inverter limits, roof constraints, permits, and manufacturer manuals.
Which calculator should I try next?
Try Solar Load Calculator, Solar Battery Bank Size Calculator, Solar Panel Count Calculator as next checks so you can compare the same decision from another angle before acting.
Method behind the estimate
Solar calculators use load, energy, voltage-drop, battery-capacity, inverter, controller, roof-fit, and payback formulas with bounded user-entered assumptions.
Why the detail matters
Treat the output as a planning worksheet. Electrical code, permits, fusing, disconnects, temperature derating, battery chemistry, roof structure, and manufacturer limits can change the real design.
No account or saved inputs
Your calculator values are for your session. CalcShelf does not require an account, save calculator entries, or add your numbers to shareable URLs.
Copy or print safely
Use any copy, print, or worksheet controls as local handoff tools for your own notes, supplier calls, lender questions, or implementation checklist. They are there to help you explain the result to a human.
Before acting
Treat the result as a decision draft, not a verdict. Recheck the source numbers, run a downside case, and verify the real-world rule, quote, label, or spec that controls the final answer.
Last reviewed: May 11, 2026. See methodology and editorial policy for formulas, assumptions, rounding, review approach, and limitations. Before buying or installing solar equipment, confirm electrical code, permits, fusing, wire ratings, battery limits, roof constraints, and equipment manuals.