Calculating Solar Panel Power Requirements

I am mesmerized every time I take my project outside, hook it up to some solar panels, and it just works. Every time (except when it’s cloudy or nighttime). Natures gift of free, clean, always on energy powering my little project. How cool!

Now I have a project that I have been testing with my bench power supply. It’s powered at 6V and draws a maximum of 135mA. How do I find the right solar panel to power this project? Well it’s really pretty simple. Solar panels are usually rated at a certain Wattage and Voltage.

We know that:

So, for our project, we can determine that:

That easily we determined our project consumes 0.81W at peak. We might then decide that a 6V 1W solar panel will suit our project. The extra 0.19W is just a safety buffer to be absolutely sure we have enough power!

That’s it! Now get outside and enjoy the sun!