Solar & storage

PV String Design Estimate Calculator

A user-input-only estimate of series-string voltage and module-array nameplate power.

01 / User inputs

PV string and inverter voltage inputs

Voc(T) = Voc(ref) × [1 + βVoc × (T − Tref)] · String voltage = module voltage × modules in series · DC nameplate = module count × module power

Enter signed relative coefficient as a fraction per °C; e.g. −0.29%/°C = −0.0029/°C. Absolute V/°C coefficients are not accepted.

Temperatures are module/cell temperatures, not ambient air temperatures.

Module open-circuit voltage (Voc)

Module maximum-power voltage (Vmp)

Module nameplate power

Signed relative Voc temperature coefficient

1/°C

Reference module/cell temperature

°C

Minimum module/cell temperature

°C

Maximum module/cell temperature

°C

Modules per series string

modules

Parallel string count

strings

Inverter maximum DC voltage

Inverter MPPT minimum voltage

Inverter MPPT maximum voltage

02 / Estimate

PV string design estimate

Enter all parameters

Enter all explicit parameters to calculate.

Method and boundaries

Applies the signed relative Voc temperature coefficient you enter to the module or cell temperature. Reference-condition Vmp and parallel-string arithmetic are shown without current, MPPT-operability, compatibility or compliance conclusions.

FAQ

What does this calculator compute?

It applies the signed relative open-circuit-voltage temperature coefficient you enter to the module or cell temperature, and it shows reference-condition maximum-power voltage and parallel-string arithmetic.

What inputs do I supply?

Supply the module voltages, the temperature coefficient, the temperatures, and the string counts shown on the form. The tool does not look up a module datasheet.

What conclusions does it avoid?

It does not conclude current rating, MPPT operability, electrical compatibility, or code compliance.

Source records

NREL SAM system design (SRC-028)
Institution: NREL
Section: String voltage, module count, nameplate power, and inverter voltage-window relationships
URL on the calculation record: https://samrepo.nlr.gov/help/pv_system_design.html
Verification date: 2026-10-12
Status: review-required
NREL SAM module (SRC-029)
Institution: NREL
Section: Reference-condition Voc, Vmp, power, and temperature-coefficient definitions
URL on the calculation record: https://samrepo.nlr.gov/help/pv_module.html
Verification date: 2026-10-12
Status: review-required
Photovoltaic plants technical application paper (SRC-030)
Institution: ABB
Section: Example of a signed relative Voc temperature coefficient. It does not validate a module.
URL on the calculation record: https://library.e.abb.com/public/fb75869122d24b408ab985833cd472db/9AKK107492A3277%20Photovoltaic%20plants%20-%20Technical%20Application%20Paper.pdf
Verification date: 2026-10-12
Status: review-required