PV string voltage formulas
Formula chart for PV string voltage, temperature adjustment and module-count relationships.
PV string voltage formulas explains formula chart relationships for Australian solar, battery and ev records. Show PV string voltage formulas without replacing product, inverter, DNSP or authority checks. Read the variables, formula notes and PV string voltage handoff before using the relationship with entered site values, product data, DNSP conditions or competent review.
PV string voltage relationships for product records
Use these row summaries to read the calculation relationship before checking the value table.
Coefficient conversion
Convert datasheet percent per deg C into a decimal coefficient.
coeff_decimal = coeff_pct / 100Cold open-circuit voltage
Adjust module open-circuit voltage for cold design temperature.
Voc_cold = Voc x (1 + (coeff_pct / 100) x (T_cold - 25 deg C))Cold operating voltage
Estimate the cold operating point for MPPT review.
Vmp_cold = Vmp x (1 + (coeff_pct / 100) x (T_cold - 25 deg C))Hot operating voltage
Estimate the hot operating point for MPPT review.
Vmp_hot = Vmp x (1 + (coeff_pct / 100) x (T_hot - 25 deg C))String voltage
Scale adjusted module voltage by modules in series.
Vstring = Vadjusted x Nseries
- Module voltage, temperature coefficient, temperature delta and module count relationships.
- Show PV string voltage formulas without replacing product, inverter, DNSP or authority checks.
- AS/NZS 5033, AS/NZS 4777, product and inverter requirements noted for project review.
- Temperature calculations use coeff_pct / 100 and T - 25 deg C context; record Voc_cold, Vmp_cold, Vmp_hot, MPPT window, datasheet, inverter limit and DNSP context.
Temperature-adjusted PV voltage formula rows
Show PV string voltage formulas without replacing product, inverter, DNSP or authority checks.
| Relationship | Formula | Use | Boundary |
|---|---|---|---|
| Coefficient conversion | coeff_decimal = coeff_pct / 100 | Convert datasheet percent per deg C into a decimal coefficient. | Coefficient sign and units must match the current datasheet source. |
| Cold open-circuit voltage | Voc_cold = Voc x (1 + (coeff_pct / 100) x (T_cold - 25 deg C)) | Adjust module open-circuit voltage for cold design temperature. | Compare with equipment maximum voltage and inverter limit before project review. |
| Cold operating voltage | Vmp_cold = Vmp x (1 + (coeff_pct / 100) x (T_cold - 25 deg C)) | Estimate the cold operating point for MPPT review. | Not a complete MPPT compatibility review without inverter datasheet context. |
| Hot operating voltage | Vmp_hot = Vmp x (1 + (coeff_pct / 100) x (T_hot - 25 deg C)) | Estimate the hot operating point for MPPT review. | Product, inverter, DNSP and project requirements still control design decisions. |
| String voltage | Vstring = Vadjusted x Nseries | Scale adjusted module voltage by modules in series. | Final count needs datasheet, inverter, DNSP and authority review. |
- Use current datasheets and inverter limits.
- The calculator owns entered project-specific values.
Formula variables
Use these symbols and units when reading the chart rows.
| Variable | Meaning | Unit | Use |
|---|---|---|---|
| Voc | Module open-circuit voltage. | V | Use the current product datasheet value. |
| Vmp | Module maximum-power voltage. | V | Use the current product datasheet value. |
| coeff_pct | Temperature coefficient percent per degree. | %/deg C | Convert with coeff_pct / 100 before applying T - 25. |
| coeff_decimal | Temperature coefficient as a decimal per degree. | 1/deg C | Derived from coeff_pct / 100. |
| T | Cell or design temperature. | deg C | |
| T_cold | Cold design temperature. | deg C | Use the selected cold design condition. |
| T_hot | Hot design temperature. | deg C | Use the selected hot operating condition. |
| T - 25 | Temperature delta from STC. | deg C | Use the selected cold or hot design temperature. |
| Vadjusted | Temperature-adjusted module voltage. | V | Use Voc_cold, Vmp_cold or Vmp_hot depending on the row. |
| Voc_cold | Cold adjusted open-circuit voltage. | V | Compare with equipment maximum voltage. |
| Vmp_cold | Cold adjusted operating voltage. | V | Compare with the inverter MPPT range. |
| Vmp_hot | Hot adjusted operating voltage. | V | Compare with the inverter MPPT range. |
| Nseries | Modules connected in series. | Use the proposed string count from the design record. | |
| Vstring | String voltage after multiplying by modules in series. | V | Compare with equipment or MPPT boundaries as appropriate. |
| MPPT | Inverter MPPT operating window. | Check current datasheet and DNSP context. |
Worked relationship example
This example shows how one set of entered values reads through the relationship.
PV cold string Voc relationship reading
A module datasheet value is temperature-adjusted before comparing a string with equipment limits.
- Module Voc
- 49.5 V
- Temperature coefficient
- -0.28 %/deg Cconvert to -0.0028
- Cold design temperature
- -5 deg C
- Modules in series
- 12
- Convert coefficientcoeff = coeff_pct / 100 = -0.28 / 100 = -0.0028 per deg C.
- Apply temperature deltaT - 25 deg C = -5 - 25 = -30 deg C.
- Find cold module voltageVoc_cold = 49.5 x (1 + -0.0028 x -30) = 53.7 V.
- Find string voltageString Voc_cold = 53.7 x 12 = 644 V.
Compare this estimate with equipment maximum voltage, inverter limits, MPPT range and DNSP/project requirements.
Use the example to read the temperature relationship; product datasheets, inverter limits and approval context still control design decisions.
- Datasheet values are current for the selected module.
- Temperature basis and DNSP context are project-entered records.
Where the PV string chart belongs
Use the chart to understand the formula basis; calculators handle project-specific inputs, warnings and results.
| Item | Value |
|---|---|
| Purpose | Show PV string voltage formulas without replacing product, inverter, DNSP or authority checks. |
| How to use the source | Module voltage, temperature coefficient, temperature delta and module count relationships. |
| Standards and project context | AS/NZS 5033, AS/NZS 4777, product and inverter requirements noted for project review. |
| Where judgement is still needed | Use this chart to understand the relationship behind a calculation; do not treat it as a substitute for entered project values. |
| Before relying on it | Confirm current standards, local authority requirements, DNSP conditions, project documents and manufacturer data before relying on a decision. |
| Context | Applies to | Public boundary |
|---|---|---|
| AS/NZS 5033, AS/NZS 4777 and product context | PV string voltage, module count and inverter compatibility records | The chart does not approve a design or reproduce controlled standards text. |
| Datasheet and inverter limits | Voc_cold, Vmp_cold, Vmp_hot, equipment maximum voltage and MPPT range | Use current module and inverter datasheets before making product or string-count decisions. |
| DNSP and project boundary | Connection context and final design review | DNSP, local authority and project requirements can override worksheet estimates. |
Formula basis for PV string voltage
Review the cited calculator source, module datasheet basis, inverter boundary, DNSP context and Australian project limits before using these PV string formulas.
| Item | Value |
|---|---|
| Source | AUWiring PV string voltage calculator formula notes. |
| Source type | Product and project record model |
| Derivation basis | Derived from AUWiring calculator logic and user-entered module data; no product listing or controlled standards text is reproduced. |
| Last checked | 2026-07-13 |
| Review interval | Annual or when PV calculator formulas, product-data practice or Australian energy-system requirements change. |
| Review trigger | Formula change, standards update, product limit change or project feedback. |
| Version used | R27-2026-07-13 |
| Australian application | Australia; product listings, inverter limits, DNSP and authority requirements govern final decisions. |
Use a calculator for project values
Use the chart to read the formula relationship, then open a calculator when you need entered project values, warnings and result context.