SolarMathKit

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Panel array topology

Solar panel series and parallel calculator

Enter one panel's datasheet values and a proposed series-parallel layout.

Check a panel array layout

Use one panel's current datasheet values.

Cold-weather Voc checkOptional pair

Enter both values to estimate cold array Voc, or leave both blank.

Layout comparison and controller limitOptional inputs

Enter a total panel count to compare every equal-count series × parallel layout. A controller limit is checked only against cold-corrected Voc.

Enter both cold-weather values before entering a controller voltage limit. Leave the limit blank to show cold Voc without a pass/fail result.

Your planning estimate

Local calculation

Enter your values, then calculate. Results will show the formula inputs and rounding used.

Formula used

array voltage = panel voltage × panels in series; array current = panel current × parallel strings; cold Voc = panel Voc × [1 + βVoc × (cold °C − 25°C)] × panels in series; headroom = PV input limit − cold array Voc

Series-connected matching panels add voltage while current stays at one string's value. Parallel strings add current while voltage stays at one string's value. The optional comparison lists every positive factor layout for the total panel count you enter. A controller or inverter voltage check uses cold-corrected Voc only when both cold-weather values and a maximum PV input voltage are supplied.

See the full assumptions and rounding policy.

Maintenance and verification

Maintained by: SolarMathKit Formula version: 1.3.0 Last reviewed:

The calculator calls the shared, tested TypeScript calculation modules documented in the methodology. Automated tests cover published examples, invalid inputs, rounding, and result invariants.

SolarMathKit maintains this implementation. The review is an internal technical check, not an independent engineering certification.

Worked example: six panels as 2S × 3P

Each panel is 49.5V Voc, 41.5V Vmp, 10.4A Isc, and 9.65A Imp.

  1. Array Vmp: 41.5V × 2 in series = 83V.
  2. Array Imp: 9.65A × 3 parallel strings = 28.95A.
  3. Array Voc at STC: 49.5V × 2 = 99V.
  4. Array Isc at STC: 10.4A × 3 = 31.2A.
  5. Total panel count: 2 × 3 = 6.
  6. For six panels, the comparison lists 1S × 6P, 2S × 3P, 3S × 2P, and 6S × 1P; array power stays the same while voltage and current change.
  7. If a maximum PV input voltage is entered, each layout's cold-corrected Voc is compared with that limit and the remaining headroom is shown when it passes.
Result: The proposed array is 2S × 3P with 83Vmp, 28.95A Imp, 99V Voc, and 31.2A Isc at STC. It remains a planning estimate, not an automatic layout recommendation.

Common mistakes to avoid

  • Adding current for panels in series.
  • Adding voltage for parallel strings.
  • Comparing STC Voc to a maximum input limit without a cold-temperature check.
  • Treating the equal-count comparison as an automatic best-layout recommendation.
  • Using values from visually similar panels instead of the exact current datasheet.

Questions people ask

What is the difference between Voc and Vmp?

Voc is open-circuit voltage; Vmp is the operating voltage at the maximum-power point under stated test conditions. Equipment documentation usually specifies different limits for each operating condition.

How does the equal-count layout comparison work?

Enter the total number of matching panels you want to compare. The calculator lists every positive factor pair as panels in series × parallel strings. It reports the same total power for each layout but does not select a best one.

How does the controller voltage check work?

Enter a documented maximum PV input voltage together with the panel Voc temperature coefficient and coldest expected temperature. The check compares that limit with cold-corrected array Voc and reports pass/fail plus voltage headroom; it never substitutes STC Voc.

Does this choose a charge controller?

No. It checks only the PV voltage limit you enter. Use the charge controller calculator next to add battery charging voltage, planning margins, and other documented limits.

Why is cold Voc optional?

The topology calculation works from STC values alone. Cold Voc is required for a controller maximum-voltage check, so both the exact panel coefficient and a defensible site design temperature must be entered.

Can I mix different panels?

This tool assumes matching panel electrical characteristics. Mixed strings require equipment-specific analysis beyond this calculator.

Before you build: Check voltage, current, temperature, protection, cable sizing and installation rules with the equipment manuals and a qualified professional.