12V 24V
12V 24V

Solar Charge Controller Calculator

This is a simple solar charge controller calculator to help you figure out exactly what size system you need. Please note, there are a few complexities in this choice and it will depend on how you wire you solar panels (serial or parallel).

The online tool below gives you a quick answer to the question 'what size solar charge controller do I need?'

We do recommend that you talk to one of our experts to make sure you are designing your electrical system in an efficient and safe way. (We offer a 30min Consultation, or a full Electrical Design Service)

The Basics of Solar Charge Controller Choice

Solar charge controllers are defined in Amps, typically 10, 20, 30, 50, 75Amps. It is important to choose the correct size Solar Charge Controller because if it is underrated you could either damage the unit or cause overcharging and damage to your battery.

Once you know the size of your solar array, if you are going to wire them in series, it is easy to specify your solar charge controller.

(Solar Panel Watts / System Voltage) x 1.1

The 1.1, adds 10% to the calculation as a margin of safety.

For example:
(500W Solar Array / 12V) x 1.1 = 45.8Amps In this circumstance, a 50Amp solar charge controller would do the job just fine. (Based on wiring your Solar Panels in Parallel)

camper van electrical system safety components

Parallel vs Series - How Should I Wire My Solar Panels? 

How you wire your solar panels is important and impacts the design of your system. In short, if you wire your solar panels in parallel you will need a larger solar charge controller. 

Series wiring In series, the system’s voltage is added up, while the amps are not. This means you can use a lower amp-rated solar charge controller. 

Parallel wiring In parallel, the voltage stays the same, but the amps are multiplied - requiring a larger (and more expensive) amp-rated solar charge controller. 

As batteries often require a higher voltage in order to charge, panels in series mean that you are able to charge your system for longer periods of the day. 

There are also advantages to parallel wiring - if one panel is covered by shade (say a close tree) - the others will continue to produce electricity. In a series system, the whole array is taken out. 

Personally, I always wire my panels in series because it means I can use a cheaper Solar Charge controller. 

Usually, you park fully in the sun when you need solar - if the sun moves behind something and casts shade - the difference in gain while one panel is shaded (and the others are not) is not so much.