Solar System & String Sizing

The Calculators

Switch between tools with a click, or use the ← → arrow keys.

System Inputs

01 / Sizing

How to use: Enter plant capacity and panel/inverter specs. We'll size the array, strings, DC/AC cable, earthing and MCCB — all in one go.

System Capacity kW Total DC plant capacity in kilowatts. Enter a positive kW value (e.g. 10).

Panel Power Wp Rated peak power per module. Enter a positive Wp value.

Panel Voc V Open-circuit voltage at STC. Enter a valid Voc in volts.

Panel Vmp V Max-power voltage at STC. Enter a valid Vmp in volts.

Voc Temp Coeff. %/°C Typically -0.25 to -0.35 %/°C. Enter a temperature coefficient.

Inverter Max DC V Absolute maximum DC input voltage. Enter the inverter's max DC voltage.

Inverter Min MPPT V Lower bound of MPPT window. Enter the inverter's min MPPT voltage.

AC Cable Length m One-way run length in metres. Enter a positive length in metres.

AC Installation Method Determines ampacity column used.

AC Cable Type Auto-selected Auto-switches to multicore for >7 kW.

Min. Site Temp °C Record low ambient. Enter a minimum site temperature.

Max. Site Temp °C Record high ambient. Enter a maximum site temperature.

Results — Sized

01 / Output

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Panels

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Inverter (kW)

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Strings

Min. Panels per String	–
Max. Panels per String	–
String Configuration	–
DC Wire	–
Phase / Cable Type	–
AC Wire (Aluminium)	–
Earthing Wire	–
MCCB	–

Show formula details

DC wire is fixed at 4 sqmm/6 sqmm per string. For High Altitude & High Temperatue Region use 6 sqmm DC wire. AC wire — full-load current from inverter kW, +20% safety margin, PF 0.8, checked against catalogue ampacity and a 3% voltage-drop limit. Phase auto-selects from capacity (≤ 7 kW → single-phase, > 7 kW → three-phase). Voltage drop is computed at design current (post-derating). For full control, use the AC Wire Sizing tab.

AC Wire Sizing

03 / Cable

How to use: Enter your inverter kW, phase, cable length and voltage-drop limit. We pick the smallest standard aluminium cable that clears both current and Vd.

Inverter / Load Capacity kW Rated AC output or connected load. Enter a positive kW.

System Type Sets phase voltage & VD formula.

Power Factor Use 0.8 as a safer design buffer. Enter PF between 0.1 and 1.

One-way Cable Length m Distance from inverter to panel. Enter a positive length.

Cable Type Auto-selected Auto-set by System Type. Editable.

Installation Method Chooses ampacity column.

Derating Factor 0.5–1. Use 1 for no derating. Enter derating between 0.5 and 1.

Safety Margin on Current % Standard: size cable for ~120% of design current. Enter 0–100.

Max Allowable Voltage Drop % Common limit: 3% for PV AC runs. Enter a positive percentage.

Results — Selected

03 / Output

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Recommended Cable

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Required (A)

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Actual Vd

System Voltage	–
Full Load Current	–
Design Current (after derating)	–
Required Current (with safety margin)	–
Cable Type / Installation	–
Recommended Cable Size	–
Actual Ampacity	–
Actual Voltage Drop	–
Actual Voltage Drop (Volts)	–

Show formula details

Required current = design current × (1 + safety margin). We scan standard Aluminium sizes and pick the first where ampacity ≥ required current and Vd ≤ your allowed limit. Voltage drop is computed at the design current (post-derating) using AC resistance at 70 °C conductor temperature. Single-phase uses Vd = 2·I·L·R/(1000·V); three-phase uses Vd = √3·I·L·R/(1000·V).

Size the sun, string by string. Wire it right.

Panels, strings and BOS — sized from your plant capacity.

Fit a fixed panel count inside the MPPT window.

Ampacity-safe, voltage-drop compliant.