How many solar panels per string (modules per string)?

The number of modules per string is set by the system voltage window: the upper limit is the system voltage (1000V or 1500V) divided by the temperature-corrected open-circuit voltage (Voc at minimum site temperature); the lower limit ensures the string voltage exceeds the inverter MPPT minimum at operating temperature. For a 1500V system with a typical 590W TOPCon module (Voc 52.6V, −0.24%/°C) at a minimum temperature of +22°C, the upper limit is floor(1500 / (52.6 × 1.0072)) = 28 modules/string. The practical default is 2 below the upper limit to leave engineering headroom.

How is inverter count calculated for a solar system?

Inverter count is the higher of two constraints: (1) the number of available string inputs — total strings divided by the maximum string inputs per inverter; (2) the power ratio — DC array capacity divided by (inverter AC rating × target DC/AC ratio). The DC/AC ratio for commercial projects is typically set between 1.1 and 1.3 to allow for irradiance peaks and reduce cost per kWh.

What DC cable cross-section is required for solar strings?

DC cable cross-section is sized to keep voltage drop within the allowed limit (typically 1% of string voltage). The formula is: A = (2 × L × Imp) / (σ × ΔV), where L is the maximum cable run length, Imp is the module operating current, σ is copper conductivity (56 S·m/mm²), and ΔV is the allowed voltage drop (V_string × drop%). The result is rounded up to the nearest standard cross-section: 4, 6, 10, 16 or 25 mm². For most commercial rooftop projects with runs under 80m, 6 mm² is sufficient.

What string fuse rating is required for a solar PV system?

String fuse rating is calculated as Isc × 1.5, then rounded up to the nearest standard fuse size. For a module with Isc = 13.87A, the minimum fuse is 13.87 × 1.5 = 20.8A, selecting the next standard size: 25A. String fuses are required when more than two strings are connected in parallel.

How many shipping containers does a solar project require?

Container count is the higher of: (1) modules only — total module count divided by the number of modules that fit in one 40HQ (22,000 kg ÷ module weight); (2) total cargo weight — (modules + mounting hardware) × 1.05 BOS factor, divided by 22,000 kg. For a 500kW system with 590W modules at 31.9 kg each, approximately 689 modules fit per 40HQ, so 858 modules requires 2 containers on modules alone.

Free tool · OmniSol Global

PV System Configurator

Enter capacity + module/inverter datasheet values → get string sizing, inverter count, cable cross-section, protection ratings and an indicative FOB budget. Accuracy ±20–40%. Not a formal quotation.

Module Parameters

Rated power (W)

300–800 W

Voc (V)

Open-circuit voltage

Vmp (V)

Must be < Voc

Isc (A)

Short-circuit current

Imp (A)

Must be < Isc

Voc temp coeff (%/°C)

Typically −0.24 to −0.30

Max system voltage (V)

Length × width (mm)

Module dimensions

Weight (kg)

15–45 kg

Always verify with the official datasheet — values vary by manufacturer even at the same rated power.

Inverter Parameters

Rated AC power (kW)

MPPT min voltage (V)

Startup threshold

Max input voltage (V)

Max string inputs

Per inverter

Project Parameters

DC capacity target (kW)

10–50,000 kW

Site min temperature (°C)

Use lowest recorded / design temp

Longest cable run (m)

String → inverter, one way

Mounting / roof type

Affects unit weight and estimated mounting cost

These are standard wind-zone baseline values. High-wind / cyclone sites may require 50–100% more mounting material. Use the wind load calculator for site-specific support spacing.

Advanced optionsDC/AC ratio · voltage drop · layout

Target DC/AC ratio

Typical: 1.1–1.3

Max DC voltage drop (%)

Inverter layout

Number of roof surfaces

DC isolation switchInclude DC isolator per inverter

Required in AU (AS/NZS 5033) and some EU markets

Modules per string override

Calculated default: 26 | valid range: 5–28

Configuration Results

Auto-updates

String Design

Voc at T_min (corrected)

52.98 V

52.6V × temp factor

System voltage limit

1500 V

Max modules/string (N_max)

Min modules/string (N_min)

MPPT start threshold

Modules/string (default)

N_max−2 = 26, clamped to [5, 28]

Array Configuration

Total strings

Total modules

858

Actual DC capacity

506.2 kW

+1.2% vs target ✓

Inverters

Inverter count

2 × 250 kW

Strings per inverter

17 (last: 16)

DC/AC ratio (actual)

1.01

DC/AC ratio 1.01: configuration is well-balanced.

DC Cable

Required cross-section

≥ 2.04 mm²

Selected standard size

4 mm²

Estimated total length

~3,300 m

Rough estimate only

Protection Devices

String fuse

25 A

Isc × 1.5 = 20.8 A

DC main breaker / inverter

400 A

17 str × Imp × 1.25

SPD units

DC/AC per inverter + main panel

Mounting & Container

Mounting weight est.

~5,541 kg

Standard wind zone baseline

Containers (40HQ)

Modules + mounting

Indicative FOB Budget — 2026-06

Modules (858 modules / 506.2 kW @ $0.13/W)$65,809

Inverters (2 × 250kW)$11,000

Mounting structure$25,311

Electrical BOS$20,249

Preliminary budget range (−10% / +15%)

$110,132 – $140,724

≈ $0.218–$0.278/W FOB China

Refine mounting with the Wind Load Calculator →

Price basis: 2026-06 China FOB. Module prices fluctuate weekly (accelerated since April 2026 export-tax change). Formal quotes valid 7–14 days only.

Scope & Limitations — Please Read

Mounting is estimated at standard wind-zone baseline. Actual quantity depends on site wind/snow load. High-wind and cyclone sites may require 50–100% more material. Use the wind load calculator (AS/NZS 1170.2 / ASCE 7-22 / EN 1991-1-4) for accurate support spacing and mounting BOM.
Electrical BOS uses typical-layout estimates. Actual cable quantity depends on inverter placement, roof plan and routing path. A roof layout sketch is required for a precise quote.
Module and inverter parameters must come from the official datasheet. Voc/Vmp values differ across manufacturers even at the same rated wattage and directly change string design.
Price assumptions are based on 2026-06 China FOB market. Module prices have fluctuated weekly since April 2026 (export tax change). Formal quotes are valid for 7–14 days only.
This tool covers DC side to inverter AC output. Main switchboard, metering, grid connection approval (SP/EMA Singapore, NEM Malaysia, AS/NZS 4777 Australia, etc.) are the EPC's scope.
Energy storage is not included. Specify storage requirements separately when requesting a quote.
All pricing is FOB China port (Ningbo / Xiamen). Ocean freight, destination port charges, import duties and installation are excluded.

Engineering Reference

How This Configurator Works

How to use this tool

Enter four groups of inputs — module datasheet parameters, inverter datasheet parameters, project capacity and site conditions. The tool applies the electrical design equations used by PV engineers and returns a preliminary BOM and indicative FOB budget. It is not a certified design document.

How many solar panels per string?

The upper bound is the system voltage (1000V or 1500V) divided by the temperature-corrected Voc at the site minimum temperature. The lower bound ensures the string voltage exceeds the inverter MPPT minimum. Formula: Voc_corrected = Voc × (1 + TempCoeff/100 × (T_min − 25)). The tool defaults to two below the upper limit to leave engineering headroom.

N_max = floor(V_sys / Voc_corrected)

How is inverter count calculated?

Inverter count is the higher of two constraints: (1) total strings ÷ max string inputs per inverter; (2) DC array capacity ÷ (inverter AC rating × target DC/AC ratio). For a 506 kW array targeting DC/AC 1.2 with 250 kW inverters: need at least ceil(506 / (250 × 1.2)) = 2 inverters. The tool picks the more conservative value.

What DC cable cross-section is required?

Cable is sized to keep voltage drop within the allowed limit (typically 1%). Result is rounded up to the nearest standard size: 4, 6, 10, 16 or 25 mm². Runs under ~80 m typically need only 4 mm²; beyond ~90–100 m, step up to 6 mm².

A = (2 × L × Imp) / (56 × ΔV)

How are protection device ratings chosen?

String fuse: Isc × 1.5, rounded to next standard size (15, 20, 25, 32, 40 A). DC main breaker per inverter: strings-per-inverter × Imp × 1.25, rounded to next standard breaker (125–630 A). SPD count: two per inverter (DC and AC sides) plus one for the main panel.

What does the budget range mean?

A −10% / +15% band is applied to the midpoint to reflect lot-pricing variation, BOS layout efficiency and market movement. The midpoint uses current China FOB rates. This is not a quotation — formal quotes require module brand, inverter model, roof layout and delivery date.

How many 40HQ containers does a solar project need?

Container count is the higher of: (1) modules only — total modules ÷ modules per 40HQ (22,000 kg ÷ module weight); (2) total cargo — (modules + mounting) × 1.05 buffer ÷ 22,000 kg. For 858 × 590W modules at 31.9 kg each, about 689 fit per 40HQ → minimum 2 containers.

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