Solar
Off-Grid Solar Calculator
Off-grid array size equals daily load energy divided by retained peak-sun energy, with the entered reserve applied. Battery capacity separately covers the chosen autonomy period and usable depth.
Aggregate daily loads to estimate off-grid solar array power, battery storage, bank amp-hours, and charge-controller current.
Calculated result
Off-grid solar system estimate
Calculating…
Calculated locally in your browser
Planning math only. Verify equipment specifications and installation requirements separately.
Equipment planning
Components that meet these requirements
The specification is calculated from the result above. Product links appear only when an enabled catalog entry meets every displayed requirement.
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Calculate above to generate a parts requirement.
Cable, fuse, breaker, disconnect, mounting, grounding, and code requirements need separate equipment and installation review.
Layer B · economics
Economics estimate
Loading dated rate configuration…
State averages are editable prefills, not utility tariffs. This section is not tax, financial, or investment advice.
Data provenance: NLR PVWatts v8 grid awaiting its first private-key refresh; the visible peak-sun-hours fallback is active. EIA residential state averages updated 2026-08-13. ZIP centroids use the 2025 Census Gazetteer. No ZIP or calculator input is sent to those sources. Read the solar data provenance and limitations.
What this calculator returns
This system-level energy budget complements the existing inverter, battery-bank, and solar-cable calculators instead of replacing their equipment-specific checks.
Formula and variables
The calculation runs entirely in your browser. Static formulas, definitions, examples, and tables remain readable without JavaScript.
Daily kWh = Σ(watts × hours × quantity)/1,000; array kW = daily kWh / (peak sun hours × retained output) × reserve; battery kWh = daily kWh × autonomy / (usable depth × efficiency).
- Eannual
- Annual electrical energy use or production, in kilowatt-hours.
- Parray
- Required or installed solar array nameplate power, in kilowatts DC.
- Y
- Estimated annual AC energy produced per installed kilowatt DC.
- PSH
- Peak sun hours per day from dated static data or the visible fallback input.
- f
- Visible orientation, shading, loss, reserve, or efficiency factor used by the selected tool.
Loads are user-entered; retained output, reserve, battery depth, efficiency, and bank voltage remain visible and editable.
Worked example
| Input | Value |
|---|---|
| Daily loads | See the example load list in the calculator |
| Peak sun hours | 4.5 h/day |
| Battery autonomy | 2 days |
| Battery-bank voltage | 48 V |
The default refrigerator, lights, and pump use about 2.1 kWh/day; the calculator expands that energy budget into an array, storage bank, and controller-current estimate.
Reference table
| Load | Planning watts | Daily-use example | Daily energy |
|---|---|---|---|
| LED lighting | 10 W/lamp | 5 h | 50 Wh/lamp |
| Laptop | 65 W | 3 h | 195 Wh |
| 12 V refrigerator | 60 W average input example | 12 h equivalent | 720 Wh |
| Water pump | 500 W | 1 h | 500 Wh |
Frequently asked questions
Why is reserve included in off-grid array sizing?
The editable reserve increases planned array capacity above the average daily-energy calculation; it does not predict a specific weather sequence.
How are the load-list entries combined?
Each load's watts, daily hours, and quantity are converted to daily kWh and summed before array and storage adjustments.
Does this size the inverter and wiring too?
No. Use the linked inverter and solar-cable tools, then verify every component and protection requirement with qualified professionals.
Assumptions and limitations
- Planning estimate only; not a binding proposal or code-compliance determination.
- Weather sequences, generator backup, surge loads, controller topology, temperature, and equipment compatibility need separate review.
- Obtain a site assessment from a licensed installer.
- Actual production varies with weather, soiling, shading, degradation, and equipment.
Method and sources
Review the solar data sources, calculation methodology, and electrical formulas for the references most relevant to this calculation. The broader technical sources index records source scope and verification. Last reviewed .