A future sustainable society need to rely more on renewable energy sources. One of the most promising alternatives is solar power. However, there are inherent fluctuations accompanied with solar power, for example if the shadow of a cloud blocks the sun light on a whole solar cell it will not produce any power. This will cause problems with connecting the solar panels to the power grid. Clear sky index (CSI) is a measurement of how much of the sky that is covered by clouds, and is a key parameter for planning of large scale solar panels. This report describes the manufacturing and programming of a cheap device for calculating the so called clear sky index (CSI) over a large portion of the sky. The device contains a Raspberry PI computer with a camera module, and utilize a program that through the computer-vision library OpenCV can calculate the CSI of the images provided by the camera. The resulting prototype costs about 800 SEK, and has possibility to be improved by adding a fish-eye lens to cover a bigger area, or to be water resistant by improving the casing, without exceeding a 1000 SEK price tag.