Solar Planning Tools

Introduction

Welcome to the solar panel string calculator. Calculating how many solar panels you can connect in a single string can be daunting. Especially, when you consider that the temperature plays an important role. This calculator not only calculates based on your panel’s ratings, but also adjusts for temperature.

How To Use

To use the Solar String Calculator, you’ll need access to your solar panel’s data sheet and/or the module information sticker (usually on the back of the panel).

All but two pieces of information are located in these two panels. You’ll need the temperature coefficients (Voc for series or Isc for parallel), the voltage open circuit (Voc) or short circuit current (Isc), and the ambient temperature at which the test were conducted for the panels. In the above example it is in the blue bar on Figure TR-1-2.

You will also need to find the data on your inverter. You’ll need to know how many inputs you have and their voltage and current ranges. Keep in mind that an MPPT often has a narrower range of voltages than the actual inverter. For more information on this see my post: Solar Power System – Design and Planning

The last piece of information is something you’ll need to look up for your particular area. That is the record low temperature. Panel output changes with temperature. The colder it gets outside, the more the panels will produce. This is often overlooked when sizing panel strings, but can cause damage to your inverter if not calculated. The temperature needs to be in °C for the solar string calculator. Use the above converter if needed.

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