Off-grid solar sizing equations
Daily energy determines array energy, battery autonomy, and inverter starting capacity separately.
PPV = Edaily / (Hsun × ηsystem)Ebattery = Edaily × Dautonomy / (DOD × ηbattery)Cbat = 1000 × Ebattery / Vsystemwhere:
- PPV
- Required PV array power[kWp]
- Edaily
- Daily load energy[kWh/day]
- Hsun
- Peak sun hours[h/day]
- DOD
- Allowed depth of discharge
Seasonal hourly simulation is required for a firm system design.
How to use the Off-Grid Solar System Sizing Calculator
Estimate PV array, battery-bank capacity, and inverter power from daily energy, sun hours, autonomy, and system voltage. Start by choosing the operating mode, then enter values from nameplates, measurements, or project documents in the units shown. The result updates immediately and keeps intermediate quantities visible for review.
- Confirm the system and calculation mode.
- Enter measured or manufacturer-rated values.
- Review the primary result and intermediate metrics.
- Continue with the related protection or equipment-selection checks.
Calculation method and validation
The equations and symbol definitions above show the complete calculation basis. Inputs are checked before calculation so zero, negative, incompatible, or physically impossible combinations are flagged instead of silently producing a misleading result.
How to interpret the result
Use the main result as a starting value and read every supporting metric. Average daily energy and peak-sun-hours inputs are representative No seasonal simulation or battery aging model A passing or recommended result means the entered mathematical conditions are satisfied; it does not certify the complete installation or a particular product combination.
- Average daily energy and peak-sun-hours inputs are representative
- No seasonal simulation or battery aging model
Selection limits and next checks
Preliminary engineering estimate only. Verify the final design against the current applicable standard, local rules, manufacturer data, and project conditions. Compare the output with the current applicable standard, local rules, exact VIOX product datasheet, environmental conditions, protection coordination, and the engineer's project requirements before procurement or installation.
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Assumptions
- Average daily energy and peak-sun-hours inputs are representative
- No seasonal simulation or battery aging model
Important Warnings
- Preliminary engineering estimate only. Verify the final design against the current applicable standard, local rules, manufacturer data, and project conditions.