EleCanada
PV electrical quantities

PV string voltage calculator

Calculate open-circuit voltage for a known series string using an explicit signed temperature coefficient. Choose module-temperature endpoints or the manufacturer's cold-ambient method.

Calculation inputs

Known string and temperature basis

These are different temperature definitions. Changing method clears both temperature fields.

V DC

Use applicable manufacturer Voc data referenced to 25°C cell temperature. Confirm any required rating tolerance separately; the tool adds no allowance.

%/°C

Enter the signed percentage from the applicable module data, for example −0.30 for −0.30%/°C. Do not enter −0.003, a positive magnitude, a Pmax coefficient or a V/°C value.

modules

Identical modules in one known series string. Parallel string count does not multiply this voltage. Module-level power electronics need a different method.

°C

Supported minimum module/cell temperature. It is not automatically the outdoor air temperature.

°C

Supported maximum module/cell temperature, at or above the minimum. The tool does not estimate it from ambient temperature or NOCT.

V DC

A user-verified applicable upper bound for this numerical comparison. The tool does not select the governing equipment/code limit or treat an MPPT voltage range as an absolute maximum.

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Known-string Voc

Enter the module data, series count, temperatures and supplied limit.

This is a linear, temperature-only Voc model. No irradiance, rating tolerance, ageing, mismatch, transient or additional design factor is applied. Confirm the actual module's supported method and range.

The comparison is arithmetic, not equipment acceptance or code approval. It does not establish MPPT/startup operation, a permitted string length, conductor sizing or an approved Canadian installation.

Match the temperature definition to the method

In module-range mode, enter the known minimum and maximum module/cell temperatures. In cold-ambient mode, enter the lowest expected site ambient temperature as defined in the applicable Canadian Solar instructions; this mode reports only that cold correction and the 25°C reference. The calculator does not convert ambient to module temperature.

Both modes require module data compatible with a 25°C reference and a non-positive signed Voc coefficient. Use matching modules and check the manufacturer's permitted calculation range. Inputs and results stay in the page and are not saved or transmitted.

Method and worked example

Convert the supplied coefficient β from %/°C to a fraction by dividing by 100 once. The correction factor is f(T) = 1 + (β/100) × (T − 25). Module Voc(T) = Voc at STC × f(T); string Voc(T) = modules in series × module Voc(T).

For a non-positive coefficient, the minimum supplied temperature gives the largest Voc within the supplied interval. The 25°C reference is reported separately and is not necessarily inside that interval. The cold-ambient method uses only its supplied lowest temperature, which must be no greater than 25°C in this tool.

Example: 40 V STC Voc, −0.30%/°C and 12 modules in series give 544.8 V at −20°C and 422.4 V at a known 65°C module temperature. The 25°C reference is 480 V. Against a supplied 600 V upper limit, the numerical difference is 55.2 V. These are hypothetical inputs, not module ratings, local design temperatures or an approved string.

Full precision is retained in arithmetic; display rounds to three decimals or scientific notation. Below/at/above comparisons use unrounded numbers and no hidden acceptance tolerance. A small apparent display difference can be rounding rather than equal inputs.

What a Voc result does not establish

Voc is open-circuit voltage, not operating voltage at maximum power. Do not use a hot Voc result as minimum Vmp or proof that an inverter can track or start. The calculator has no Vmp coefficient, current model, inverter operating window or module-level electronics model.

A supplied upper limit must be verified against the actual module, inverter, controller and other applicable equipment and installation requirements. This tool does not identify the governing limit, add a required allowance or recommend how many modules to install. Manufacturer certification and jurisdiction-specific design approval remain separate.

Common questions

Why does the temperature coefficient need a minus sign?

For the supported silicon-module model, the supplied non-positive coefficient makes voltage rise as temperature falls. The input is a signed percent per degree, not an absolute magnitude. Use the actual Voc coefficient; power and operating-voltage coefficients describe different quantities.

Can I enter ambient temperatures in module-range mode?

Only if supported data establishes that they are the relevant module temperatures. Ambient and module temperature are different. Use the separate manufacturer's cold-ambient mode only when its method applies to the actual module and installation context.

Does “below the supplied limit” mean the string is acceptable?

No. It compares this model's cold-end value with one number you supplied. Required margins, governing limits, other ratings, MPPT operation and local design requirements have not been checked.

Voltage dropEstimate voltage loss or maximum distance from supplied impedance.Battery runtimeEstimate runtime from available energy and load.Electrical relationshipsSolve DC quantities, convert AC power/current, compare PF current ratios, or relate balanced wye voltages.

Sources and scope

Province of British Columbia / Industry Training Authority, Construction Electrician Level 4, H-8: Install Alternative Power Systems, version 1 (December 2015), printed page 64 / PDF page 64: Voc temperature correction from a 25°C module reference. Only the physical relationship and series-voltage principle are used; its dated code examples and generic equipment values are not imported.

CSI Solar, Installation Manual of Photovoltaic Module, EN-Rev IM/GN-EU/3.3 (July 2026), section 3, printed page 3 / PDF page 5: lowest-ambient Voc correction and STC definition. The EU/general document is used for that physical method only; it does not establish Canadian product certification, a permitted system voltage or jurisdictional acceptance.

Sources checked November 10, 2026. Report a problem or suggest a source; inputs are not attached automatically.