Off Grid Solar Panel Power Sizing Calculator

This solar PV panels power sizing calculator will help you determine the solar panel wattage requirements for your off grid solar project. Please note: this calculator uses average solar insolation data - if you require a system which must function even on very low solar insolation days you will need to size your system using minimum daily solar insolation for your area.

Use the yearly deficit/surplus data in the calculator to size your system so that it will still on average supply enough energy during the lowest solar radiation months over which you will be using the system. If you are planning on using the system over summer only then choose the lowest summer solar radiation month for your location. If you require a year round more mission critical system you should size your system using minimum daily solar insolation for your area in winter.

* Assumes a true Solar North panel mounting at the optimal fixed tilt which is approximately equal to your latitude, L. Note: if you want to optimize your system for winter collection the optimal tilt angle is L + 23.5º. If on the other hand you want to optimize your system for summer collection then the optimal tilt angle is L - 23.5º.
‡ If working in Amps - a 24V battery of a certain AmpHour rating will have twice the energy of a 12V battery of the same AmpHour rating.
† Deeper discharge cycles shorten a battery's lifetime, also for this value you should consider the age of the battery.

You can also size your solar regulator wiring using our solar wire sizing calculator. You can also size your solar charging regulator by using our solar regulator sizing calculator.

Details about this Solar Calculator

  • This calculator uses data from the Australian Solar Radiation Data Handbook (T. Lee, D. Oppenheim, and T. J. Williamson, Canberra: Energy Research and Development Corporation, 1995)
  • This calculator assumes the standard derate factor of 0.7 for the solar panels.

Useful links

  • Google maps (use to estimate deviations from Solar North)

Disclaimer: This free to use calculator is provided as is. While we have endeavoured to make this calculator as accurate as possible we take no responsibility for accuracy of the assumptions, data or advice it provides. This calculator should be cross checked with other information and should not be used as the sole means in making your purchasing decisions.

Recent Blog Post Articles

Back to top