Screening use onlyResults are educational estimates. They are not verified for construction, equipment selection, or permit submission.· 2 registered heuristic groups (H-002 · H-019)Why

These calculators are undergoing a correctness audit against primary standards. Part of the logic still rests on engineering rules-of-thumb rather than rules traced to a dated edition of a code, and some published citations do not yet match the rule the code actually applies. Known defects are being fixed in sequence.

Treat every number here as a starting estimate to be checked, never as a design decision. Anything that will be built, energised, or submitted to an authority must be independently calculated and sealed by a licensed engineer who takes responsibility for the result.

Audit status: in progress · Assurance level: screening · Not for permit use

Rule-of-thumb decisions on this calculator

H-002 · screening only
Decision points: panel technology preset · battery chemistry preset · inverter DC/AC ratio and typical-efficiency guidelines · per-item system-loss preset · latitude tilt rule of thumb · market size catalogs and the 400 W reference module prefilled into the forms
Solar presets stand in for module, battery and inverter data the caller has not supplied; the engines label them as presets in their output, but they remain generic technology figures rather than product data.
Permit gate: block
H-019 · forbid permit
Decision points: assumed cell architecture of 4 cells lithium and 6 cells lead-acid · generic 1C and 0.2C continuous rates with a doubled peak · cycle-life projection scaled from the depth-of-discharge ratio · fixed bank warning thresholds
Peak and surge windows are now required alongside any peak rating, and the depth of discharge, inverter efficiency, temperature derating and unit capacity must be stated; the unit architecture, the generic C-rates and the cycle-life projection are still chemistry-level assumptions.
Permit gate: block

Screening use only — Results are educational estimates. They are not verified for construction, equipment selection, or permit submission.

These calculators are undergoing a correctness audit against primary standards. Part of the logic still rests on engineering rules-of-thumb rather than rules traced to a dated edition of a code, and some published citations do not yet match the rule the code actually applies. Known defects are being fixed in sequence.

Treat every number here as a starting estimate to be checked, never as a design decision. Anything that will be built, energised, or submitted to an authority must be independently calculated and sealed by a licensed engineer who takes responsibility for the result.

Audit status: in progress · Assurance level: screening · Not for permit use

Rule-of-thumb decisions on this calculator

H-002 · screening only
Decision points: panel technology preset · battery chemistry preset · inverter DC/AC ratio and typical-efficiency guidelines · per-item system-loss preset · latitude tilt rule of thumb · market size catalogs and the 400 W reference module prefilled into the forms
Solar presets stand in for module, battery and inverter data the caller has not supplied; the engines label them as presets in their output, but they remain generic technology figures rather than product data.
Permit gate: block
H-019 · forbid permit
Decision points: assumed cell architecture of 4 cells lithium and 6 cells lead-acid · generic 1C and 0.2C continuous rates with a doubled peak · cycle-life projection scaled from the depth-of-discharge ratio · fixed bank warning thresholds
Peak and surge windows are now required alongside any peak rating, and the depth of discharge, inverter efficiency, temperature derating and unit capacity must be stated; the unit architecture, the generic C-rates and the cycle-life projection are still chemistry-level assumptions.
Permit gate: block

CALC 18 · SOLARPREVIEW

Battery Bank Sizing

C = (E × d) ÷ (DOD × η)

Calculate the optimal battery bank size for off-grid or hybrid solar systems. Supports lithium and lead-acid technologies with lifecycle analysis.

Solar Design Workflow

Panel SizingPanels

Inverter SizingInverter

3Battery BankBattery

4String ConfigStrings

5ROI AnalysisROI

Battery Bank Sizing · Advanced Preview

Available free during the correctness audit. Results remain screening-only unless the result itself states a stronger assurance level.

ENERGY REQUIREMENTS

Daily Energy Consumption (kWh/day)

kWh

Energy you need to power from batteries

Autonomy Days (Backup Duration)

2 days

0.52 (typical)5

System Type

Battery Technology

System Voltage

Individual Battery Capacity (Ah)

Depth of Discharge: 90%

20% (conservative)90% (recommended)95% (aggressive)

Inverter Efficiency: 95%

AC round-trip efficiency of the inverter drawing from this bank. The 95% starting position is a generic figure, not a product rating — use the efficiency curve on your inverter datasheet at the expected load.

Temperature Derating Factor

Usable-capacity fraction at the installed temperature (0–1), read from the battery datasheet's temperature curve. Stating 1.00 is itself the claim that no derating applies; left blank, the calculation is refused rather than assumed.

DISCHARGE RATINGS (DATASHEET)

Invalid Input

temperatureDerating is required — capacity loss at the installed temperature is a site fact, and 1.0 (no derating) is itself a claim about the installation. It is not replaced with a default.

CALCULATION SHEET

— AWAITING INPUT —

Enter your energy requirements and select battery type to get your optimal battery bank configuration.

REFERENCE — BATTERY TECHNOLOGY COMPARISON

Type	DOD	Cycles	Life	$/kWh
LiFePO4	90%	6,000	20y	$500
Li-ion (NMC)	90%	4,000	15y	$400
Lead-Acid AGM	50%	1,200	7y	$200
Lead-Acid Gel	50%	1,000	8y	$250
Lead-Acid FLA	50%	800	5y	$150

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