Solar PV Array Sizing Calculator
Size a solar PV array from your daily energy need, peak sun hours, performance ratio and module rating, and get the number of modules, with the formula.
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Estimate only. Not engineering or safety advice. Check the result against the applicable standard and the equipment data, and have a competent engineer review it before it is relied on. Terms of use.
Open in the calculator with these values
About this calculator
Use this to turn a daily energy target into an array rating and a module count. It divides the energy by the peak sun hours and the performance ratio, then rounds the number of modules up.
Limits of this calculator
Get the peak sun hours from irradiation data for the site and the tilt of the array. Roof area, the string voltage window and the inverter size are separate checks. The string length calculator covers the voltage limit.
Cross-check: 6 reference cases, calculated from textbook formulas coded separately from the engine by the same author, agree with this calculator. This is not an independent review.
Verification status: Indicative
Indicative. Estimation only; further engineering checks are required. Basis: Sizing estimate from an energy need.
What this calculator checks
- The arithmetic of the simplified model for the values you entered.
What remains unverified
- Whether the simplifying assumptions listed on this page hold for your case.
- Any standard, manufacturer or site data. Treat the result as an estimate and confirm it by a further engineering check.
Verification register entry
| Calculation author | Rahul Sharma (author) |
|---|---|
| Technical review | No independent technical review has been carried out |
| Individual professional approval | Not recorded |
| Formula reference | not recorded |
| Standard and edition | IEC 62548-1, 2023 + AMD1:2025, consolidated version |
| Standard review state | Public-scope screened; licensed clause review still pending |
| Scope-screening note | PV-array design and DC-system protection are relevant. The energy-demand sizing formula is a preliminary estimate; module configuration, inverter limits, shading, storage and site yield require separate design checks. |
| Cross-check test cases | 6 reference vectors (tests/reference_vectors.json) |
| Review date | not recorded |
| Next review date | not recorded |
| Status | Indicative |
Needed before this calculator can be marked Verified: reviewer name, qualification and review date; licensed clause-by-clause standard review; exact formula reference; formula source (textbook or standard); next review date.
Formula
Worked example
| Input | Value |
|---|---|
| Daily energy needed | 30 kWh |
| Peak sun hours per day | 5 |
| Performance ratio | 0.75 |
| Module rating | 550 W |
- Parray = 30 kWh / (5 × 0.75) = 8 kW
- Modules = 8,000 / 550 = 14.55, rounded up to 15
Assumptions
- PSH is the daily irradiation on the module plane in kWh/m²
- Performance ratio covers temperature, soiling, cable and inverter losses
Get PSH from site irradiation data. Roof area, string voltage window and inverter size are separate checks.
Inputs and results
| Input | Unit | Allowed or shown | Note |
|---|---|---|---|
| Daily energy needed | kWh | greater than 0 kWh | |
| Peak sun hours per day | (number) | 0.5 or more, up to 9 | |
| Performance ratio | (number) | 0.3 or more, up to 1 | 0.7 to 0.8 for a typical grid-tied system, lower with batteries |
| Module rating | W | greater than 0 W |
| Result | Unit | Allowed or shown | Note |
|---|---|---|---|
| Array rating | kW | Shown to 2 decimal places | |
| Modules needed | (number) | Shown to 0 decimal places |
How it is calculated
Each input is converted to the base unit of its quantity, the formula above is applied in the order shown in the worked example, and each result is shown in the unit you choose. Results are held at full precision and rounded only for display, except where a step selects a standard size, as the worked example shows. A value outside its allowed range is refused with a message instead of giving a result.
Typical values
| Daily energy needed (kWh) | Array rating (kW) | Modules needed |
|---|---|---|
| 5 | 1.33 | 3 |
| 10 | 2.67 | 5 |
| 30 | 8 | 15 |
| 60 | 16 | 30 |
| 100 | 26.67 | 49 |
Other inputs are the same as in the worked example above.
Standards and further reading
- IEC 62548 (photovoltaic array design requirements)
Module and battery limits come from the manufacturer data sheet; local grid codes set connection rules. These are named as background reading. Elecmetric does not embed clause text or rating tables, and the reviewer record for this calculator is separate from this list.
Frequently asked questions
What do I need to enter?
Enter daily energy needed, peak sun hours per day, performance ratio and module rating. Change the unit of a value with its selector and the result stays the same.
What are peak sun hours?
The daily solar energy on the module plane in kWh per square metre, which is equal to the hours of full sun at 1 kW per square metre. It depends on the site, season and tilt.
What does the performance ratio cover?
The losses between the nameplate rating and the energy delivered: temperature, soiling, cable and inverter losses. Use a value you can justify for the site and the equipment.
How many modules fit in a string?
That is a voltage question, not an energy one. Use the solar PV string size calculator, which limits the number of modules so the cold-weather open-circuit voltage stays under the system limit.
How accurate are the results?
Every figure comes from the same tested engine as the Elecmetric calculators and is meant for estimating. 6 reference cases, calculated from textbook formulas coded separately from the engine by the same author, agree with this calculator. This is not an independent review. Check design values against the standard and the equipment data you work to.
Formula guides and reference
Longer explanations with worked examples and tables, written for the same topic.
- Solar PV Formulas: Array Size and Strings: Solar PV formulas for array size from daily energy, yearly yield
- Solar DC to AC Ratio Formulas: Solar DC to AC ratio formulas: the array size, the ratio of array power to inverter power and the inverter size for a…
- Solar Energy Yield and Degradation Formulas: Solar PV yield formulas: the yearly energy from array size, peak sun hours and performance ratio
- Solar Charge Controller Sizing Formulas: Charge controller formulas: the output current of an MPPT controller from the array power and battery voltage
- Solar Array Row Spacing Formulas: Solar row spacing formulas: the solar altitude at the winter solstice, the shadow length
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