Which module temperature coefficient should I enter?

Use the voltage coefficient from the module datasheet. Enter it as a negative percent per degree C value, not as the absolute magnitude.

Why does cold temperature increase Voc?

A negative voltage coefficient means module voltage rises when the cell temperature is below 25 deg C. That is why cold Voc is usually the maximum-voltage check.

Can this confirm inverter compatibility?

No. The worksheet compares entered voltages only. Inverter compatibility also depends on product listings, input grouping, current, firmware, installation requirements and manufacturer instructions.

Should I use ambient temperature or cell temperature?

Use the temperature basis required by the project method and product documentation. The hot operating check normally needs a cell-temperature assumption, not only ambient air temperature.

What should I record before exporting?

Record the string reference, module count, module datasheet source, inverter limit source, cold temperature, hot cell temperature and calculated voltage margins.

PV string voltage calculator

String reference*

Choose a common string reference, or select Custom for a project-specific array or drawing label.

Modules in series*

modules

Enter the proposed number of modules in this string.

Module Voc*

Enter open-circuit voltage at STC from the module datasheet.

Module Vmp*

Enter maximum-power voltage at STC from the module datasheet.

Voc coefficient*

%/deg C

Enter the datasheet coefficient as a negative percent per degree C value.

Vmp coefficient*

%/deg C

Enter the datasheet Vmp voltage coefficient, not the power coefficient.

Cold temperature*

deg C

Use the cold design temperature selected for the project string-voltage review.

Hot cell temperature*

deg C

Use a hot cell temperature assumption for operating-voltage review.

Maximum DC voltage*

Enter the equipment maximum DC input voltage from the inverter or product documentation.

Minimum MPPT voltage*

Enter the lower MPPT voltage from inverter documentation.

Maximum MPPT voltage*

Enter the upper MPPT voltage from inverter documentation.

Notes

536.58V

The calculated string voltages sit inside the supplied limits. Keep the module datasheet, temperature basis and inverter limit source with the record.

PV string reference: PV-1
Modules in series: 10
Module Voc at STC: 49.5V
Module Vmp at STC: 41.2V
Voc coefficient: -0.28%/deg C
Vmp coefficient: -0.35%/deg C
Cold design temperature: -5 deg C
Hot cell temperature: 70 deg C
Cold string Voc: 536.58V
Cold string Vmp: 455.26V
Hot string Vmp: 347.11V
Maximum DC voltage: 600V
MPPT window: 120-550V
Maximum DC margin: +63.42V
Hot MPPT margin: +227.11V
Cold MPPT margin: +94.74V

Assumptions

Voltage values and temperature coefficients are entered from module datasheet data.
Maximum DC voltage and MPPT limits are entered from equipment documentation.
The result does not approve PV array compliance, inverter compatibility, DNSP connection, string fusing, isolation, cable selection or earthing.

Vstring = N x Vstc x (1 + (coeff_pct / 100) x (T - 25))

Enter voltage temperature coefficients with their sign, normally negative for PV module voltage.
Cold Voc is usually the maximum-voltage check and hot Vmp is usually the lower operating-voltage check.
Product documentation, equipment limits and DNSP/project requirements remain controlling.

Formula variables
Variable	Meaning	Unit	Use
N	Modules in series	modules	Number of PV modules connected in series in the string.
Vstc	Module voltage at STC	V	Module Voc or Vmp entered from the module datasheet.
coeff_pct	Temperature coefficient	%/deg C	Voltage coefficient entered as a negative percent per degree C value.
T	Review temperature	deg C	Cold design temperature for Voc or hot cell temperature for Vmp.
Voc_cold	Cold string open-circuit voltage	V	Temperature-adjusted string Voc compared with the entered maximum DC input voltage.
Vmp_cold	Cold operating-voltage estimate	V	Temperature-adjusted string Vmp compared with the entered MPPT maximum.
Vmp_hot	Hot operating-voltage estimate	V	Temperature-adjusted string Vmp compared with the entered MPPT minimum.
Vmax_dc	Maximum DC input voltage	V	Entered equipment maximum DC voltage limit.
Vmppt_min	Minimum MPPT voltage	V	Entered lower MPPT voltage from inverter documentation.
Vmppt_max	Maximum MPPT voltage	V	Entered upper MPPT voltage from inverter documentation.
Margin	Voltage margin	V	Entered limit minus calculated string voltage, or calculated string voltage minus entered lower MPPT limit.

PV string voltage calculator technical guide

Check PV string cold Voc and operating voltage range from entered module data, temperature values and equipment limits for Australian solar project records.

Use this page when a PV string count needs a traceable voltage record before the design is carried into an inverter schedule, quote note, project worksheet or review pack. The calculation is only as reliable as the module data, temperature basis and equipment limits entered by the user.

The key review is usually cold open-circuit voltage. A string that looks acceptable at STC can exceed an entered maximum DC input voltage when the cold design temperature is applied. The second review is operating voltage: a short string can sit too low for the entered MPPT minimum under hot cell-temperature assumptions, while a longer string can approach the entered MPPT maximum under cold conditions.

Field use cases

Practical PV string voltage use cases
Work setting	Real question	Useful action from this page
Residential inverter schedule	Can the proposed module count stay below the entered maximum DC input voltage on a cold day?	Enter module `Voc`, `Voc` coefficient, cold temperature and inverter maximum DC voltage before carrying the string count into the schedule.
Commercial string layout	Does a longer string remain inside the entered MPPT window under hot and cold assumptions?	Review cold `Vmp`, hot `Vmp` and both MPPT margins, not only cold `Voc`.
Quote note	Which module count was used when the estimate was prepared?	Export the record with module count, datasheet source and equipment limit source attached.
Design review	Is a voltage warning caused by module data, temperature assumption or inverter limit?	Compare the three margins separately before changing the string count.
Replacement module review	Can an older string count be reused with a different module model?	Re-enter the new module `Voc`, `Vmp` and coefficients instead of reusing the old string-voltage result.

A useful string-voltage record names the string and the data source. A record that only states the module count is weak. A record that says "PV-1, 10 modules, module Voc 49.5 V, Voc coefficient -0.28%/deg C, cold temperature -5 deg C, maximum DC input 600 V, cold string Voc 536.58 V" can be checked by another person.

Module data checklist

Datasheet values to collect before using the worksheet
Value	Where it normally comes from	Why it matters
Module `Voc` at STC	Exact module datasheet and revision	Check that the value belongs to the installed module model, not a similar wattage class.
Module `Vmp` at STC	Exact module datasheet and revision	Use the voltage value for the module being scheduled, not a substitute module family.
`Voc` temperature coefficient	Module datasheet	Confirm the coefficient is a voltage coefficient and is entered with the correct sign.
`Vmp` temperature coefficient	Module datasheet	Do not use the power coefficient unless the product documentation explicitly supports that method.
Maximum DC input voltage	Inverter or equipment documentation	Confirm the limit for the exact product variant and input arrangement.
MPPT voltage range	Inverter documentation	Use the window for the specific tracker or input group being reviewed.
Temperature basis	Project method, product data or design instruction	Record which method supplied the cold and hot assumptions.

Do not substitute a power temperature coefficient for a voltage coefficient unless the product documentation explicitly supports that use. Module datasheets often list several coefficients. The worksheet expects voltage coefficients entered as negative percent per degree C values.

Do not mix the cold ambient basis used for maximum Voc review with a hot cell-temperature assumption used for operating-voltage review. Record which project method, product instruction or design basis supplied each temperature.

Cold and hot voltage interpretation

Cold Voc is a maximum-voltage check. With a negative Voc temperature coefficient, lower temperature increases module open-circuit voltage. The calculated cold string Voc is compared with the entered maximum DC input voltage. A negative maximum DC margin is a stop point for module count, equipment limit and temperature-basis review.

Hot Vmp is an operating-window check. Higher cell temperature normally reduces module operating voltage. The calculated hot string Vmp is compared with the entered MPPT minimum. A negative hot MPPT margin does not automatically condemn a design, but it is a clear sign that the string count, inverter operating window and temperature assumption need review.

Cold Vmp is also useful because it estimates the upper side of the operating-voltage range. The worksheet compares cold Vmp with the entered MPPT maximum. This is separate from maximum DC input voltage. Confusing those two limits can create a record that looks tidy while checking the wrong equipment boundary.

Limit review matrix

PV string voltage review states
Calculated value	Entered comparison	What a warning usually means	Practical review
Cold string `Voc`	Maximum DC input voltage	The string may exceed the entered equipment maximum at the cold design temperature.	Recheck module count, `Voc` coefficient, cold temperature and inverter input limit.
Hot string `Vmp`	MPPT minimum voltage	The string may sit below the entered operating window in hot conditions.	Recheck module count, hot cell temperature and inverter MPPT range.
Cold string `Vmp`	MPPT maximum voltage	The cold operating-voltage estimate may sit above the entered MPPT maximum.	Confirm the MPPT upper limit and whether the string count belongs on that input.
Margins close to zero	Any entered voltage limit	Small input changes can change the review result.	Keep datasheet revision, temperature method and equipment model visible.

The matrix is a record aid, not an approval table. It helps identify which assumption or limit is driving the result. It does not check inverter current, product listings, string fusing, isolation, earthing, array layout, shading, cable routing or DNSP connection conditions.

Review workflow

Identify the string reference from the array layout, inverter input schedule or design note.
Take Voc, Vmp and voltage temperature coefficients from the module datasheet for the exact module model.
Enter the module count in series for the string being reviewed.
Enter the cold design temperature and hot cell temperature basis used for the project record.
Enter maximum DC input voltage and the MPPT voltage window for the specific inverter input or tracker being reviewed.
Read the cold Voc margin first, then review hot and cold Vmp margins.
If any margin is negative or narrow, check the module count, data source and equipment limits before changing the design note.
Carry the exported record forward only with the datasheet source, inverter source and temperature basis attached.

This workflow keeps the calculator as a voltage worksheet. It does not select modules, assign strings to inputs, determine inverter compatibility or complete the PV array design.

Worked records

PV string voltage examples
Situation	Inputs	Result	Record use
600 V residential string	10 modules, `Voc` 49.5 V, `Vmp` 41.2 V, coefficients -0.28 and -0.35%/deg C, -5 deg C cold, 70 deg C hot, 600 V max DC, 120-550 V MPPT	Cold `Voc` 536.58 V, hot `Vmp` 347.11 V, maximum DC margin +63.42 V	PV-1: supplied 600 V max DC and 120-550 V MPPT limits are satisfied on the listed datasheet and temperature basis.
1000 V commercial string	18 modules, `Voc` 49.8 V, `Vmp` 41.5 V, coefficients -0.29 and -0.36%/deg C, -5 deg C cold, 70 deg C hot, 1000 V max DC, 250-850 V MPPT	Cold `Voc` 974.39 V, hot `Vmp` 625.99 V, maximum DC margin +25.61 V	PV-C1: maximum DC margin is narrow; keep exact module, inverter input and temperature basis with the record.
Cold-limit review	12 modules, `Voc` 50 V, `Vmp` 41 V, coefficients -0.29 and -0.35%/deg C, -10 deg C cold, 70 deg C hot, 600 V max DC	Cold `Voc` 660.90 V, maximum DC margin -60.90 V	PV-COLD: cold `Voc` exceeds the supplied 600 V maximum DC input; revise module count or equipment basis before carrying forward.

The examples show why module count is not a standalone answer. The same number of modules can be acceptable or unsuitable depending on module voltage, temperature coefficient, cold temperature and equipment limit.

Boundary with neighbouring calculations

Where this calculator stops
Related task	Use this page?	Why
Inverter AC cable voltage rise or drop	No	AC cable work belongs to the inverter AC cable workflow when that route is released.
Battery DC cable voltage drop	No	Battery cable voltage drop is a high-current DC cable task, not a PV string voltage task.
PV string current, fusing or isolator rating	No	Current and protective-device decisions need module short-circuit current, product ratings and installation requirements.
General load current	No	Use the load-current calculator for AC load current outside the PV string-voltage worksheet.
Cable voltage drop	Sometimes	Use the cable voltage-drop calculator only after current, conductor and route data are known.
Final inverter compatibility	No	Compatibility depends on product data, input allocation, listings, firmware and manufacturer instructions.

Keeping this boundary clear prevents the voltage worksheet from turning into a solar design approval tool. The output is a structured voltage record that feeds into the wider PV design and review process.

Australian context

PV array installation and inverter connection work in Australia sits inside current Australian standards, local authority requirements, DNSP conditions, equipment listings and manufacturer instructions. AS/NZS 5033:2021 and AS/NZS 4777 are relevant context for PV array and inverter work, but this page only performs the string-voltage arithmetic entered by the user. It does not reproduce controlled standard tables and does not decide whether an installation is acceptable.

In practice, this record usually sits beside the module datasheet, inverter datasheet, array layout and inverter input schedule. The DNSP or export-limit process does not replace the DC string-voltage check, and this string-voltage check does not replace inverter listing, input allocation, current, isolator, fusing, earthing or connection-condition review.

The calculator deliberately asks for datasheet and equipment values instead of embedding fixed product data. That is the safer public model for a static tool. Module models, inverter inputs, allowable voltage ranges, temperature methods and connection requirements can change by product, site and network.

Minimum export record
Record item	Why it matters
PV string or inverter-input reference	Ties the voltage result to the array layout or inverter schedule.
Module datasheet source	Confirms the `Voc`, `Vmp` and coefficient values belong to the exact module model.
Inverter or equipment limit source	Shows where maximum DC and MPPT limits were taken from.
Temperature basis	Explains the cold and hot assumptions behind the voltage margins.
Module count in series	Identifies the proposed string count being screened.
Voltage margins	Shows which limit is controlling the next review.
Reviewer	Identifies who prepared or checked the arithmetic record.

Stop points

The exact module model or datasheet revision is unknown.
The entered temperature coefficient is copied as a positive number when the datasheet expects a negative voltage coefficient.
The cold string Voc margin is negative or very narrow.
Hot string Vmp is below the entered MPPT minimum.
The MPPT window is copied from a different inverter model, MPPT tracker or input group.
Maximum DC voltage or MPPT range is copied from a different inverter variant, tracker, firmware/manual revision or input grouping.
The result is being used to choose string fuses, isolators, cables or inverter inputs without product documentation.
DNSP, local authority, manufacturer or current standards requirements are being treated as optional.

PV string reference: PV-1
Modules in series: 10
Module Voc: 49.5 V
Module Vmp: 41.2 V
Voc coefficient: -0.28%/deg C
Vmp coefficient: -0.35%/deg C
Cold design temperature: -5 deg C
Hot cell temperature: 70 deg C
Maximum DC voltage: 600 V
MPPT window: 120-550 V

Cold string Voc536.58 V
Cold string Vmp455.26 V
Hot string Vmp347.11 V
Maximum DC margin63.42 V
Hot MPPT margin227.11 V
Cold MPPT margin94.74 V

Cold string Voc536.58 V

The entered string sits inside the entered voltage limits.

The cold string Voc is below the entered maximum DC voltage and the operating-voltage estimates sit inside the entered MPPT window.

Module voltage values and coefficients are entered from the module datasheet.
The MPPT window is entered from the inverter documentation.
The worksheet does not decide PV array compliance or inverter compatibility.

PV string reference: PV-C1
Modules in series: 18
Module Voc: 49.8 V
Module Vmp: 41.5 V
Voc coefficient: -0.29%/deg C
Vmp coefficient: -0.36%/deg C
Cold design temperature: -5 deg C
Hot cell temperature: 70 deg C
Maximum DC voltage: 1000 V
MPPT window: 250-850 V

Cold string Voc974.39 V
Cold string Vmp827.68 V
Hot string Vmp625.99 V
Maximum DC margin25.61 V
Hot MPPT margin375.99 V
Cold MPPT margin22.32 V

Cold string Voc974.39 V

The entered string sits inside the entered voltage limits.

The string remains within the entered voltage window, but the maximum DC margin is small enough to keep datasheet source and temperature basis visible.

The maximum DC input voltage is an entered equipment value.
The cold temperature and hot cell temperature are project assumptions.
Parallel strings, current protection and inverter input grouping are outside this voltage worksheet.

PV string reference: PV-COLD
Modules in series: 12
Module Voc: 50 V
Module Vmp: 41 V
Voc coefficient: -0.29%/deg C
Vmp coefficient: -0.35%/deg C
Cold design temperature: -10 deg C
Hot cell temperature: 70 deg C
Maximum DC voltage: 600 V
MPPT window: 120-550 V

Cold string Voc660.9 V
Cold string Vmp552.27 V
Hot string Vmp414.51 V
Maximum DC margin-60.9 V
Hot MPPT margin294.51 V
Cold MPPT margin-2.27 V

Cold string Voc660.9 V

At least one entered voltage limit needs review.

The cold string Voc is above the entered maximum DC input voltage. The module count, equipment limit and temperature basis need review before the string is carried forward.

The cold design temperature is entered by the user.
The calculator uses the entered negative Voc coefficient directly.
The result is a stop-point record, not a final array redesign.