Solar
Solar Battery Calculator
Solar battery capacity equals daily energy multiplied by autonomy days and divided by usable depth and battery-path efficiency. Bank amp-hours then equal nominal watt-hours divided by bank voltage.
Estimate solar battery energy, amp-hours, autonomy, and a series-parallel unit count from daily use and visible storage assumptions.
Calculated result
Solar battery requirement
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
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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 page sizes autonomy energy. The existing Battery Bank Calculator remains the direct series/parallel geometry tool, so the two URLs serve different intents.
Formula and variables
The calculation runs entirely in your browser. Static formulas, definitions, examples, and tables remain readable without JavaScript.
Nominal battery kWh = daily kWh × autonomy days / (usable depth × efficiency); bank Ah = nominal Wh / bank voltage.
- 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.
Depth of discharge and efficiency are visible user percentages; series and parallel counts use the entered unit voltage and amp-hours.
Worked example
| Input | Value |
|---|---|
| Daily energy use | 10 kWh/day |
| Days of autonomy | 2 days |
| Usable depth of discharge | 80 % |
| Battery-path efficiency | 92 % |
A 10 kWh/day load with two autonomy days, 80% usable depth, and 92% efficiency needs about 27.2 kWh nominal before rounding to whole battery units.
Reference table
| Battery family | Illustrative usable depth | Planning note |
|---|---|---|
| Lithium iron phosphate | 80–90% | Verify cell, pack, and BMS limits |
| Lead-acid | 50% | Deeper cycling can reduce life |
| Unknown chemistry | User must enter | Do not infer a safe value from this table |
Frequently asked questions
How do autonomy days affect battery size?
Required nominal storage rises directly with the number of days the battery must support the entered daily energy use.
Why do usable depth and efficiency increase nominal capacity?
The bank must store more nameplate energy because only the usable fraction reaches the loads after the entered conversion losses.
How is this different from the Battery Bank Calculator?
This page starts with daily energy and autonomy to estimate required storage; the Battery Bank Calculator starts with chosen units and reports their series-parallel totals.
Assumptions and limitations
- Planning estimate only; not a battery-system design or code-compliance determination.
- Temperature, aging, discharge rate, BMS limits, fire safety, and manufacturer pairing are outside the model.
- Obtain a site assessment from a licensed installer.
- Any cost comparison is not tax, financial, or investment advice.
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 .