The App Solar Consult can calculate for you the output of solar panels. With this tool for comparing solar panels displays the optimal output of solar panels. Interestingly, the solar panels now looked a lot nicer then a few years ago and a lot of black panels are offered. The panels are also standard equipped with partitions so that the weather will not affect the setup.
My father has installed 13 black solar panels of 315 Wp on his roof and the cables are neatly concealed in plastic tubing. The reason for choosing this supplier was (in addition of the good price) that we have received a certificate after the installation. With this certificate, an output of 3,750 kWh per year was guaranteed and this will be checked after five years and after ten years (online). If the panels have less output than described in the certificate, the difference will be paid for $0.20 per kWh.
For this, the converter was connected to our network via WiFi and can be reached online via their website (after logging with his account) to see the revenue per day, per month and in the entire period after installation.
We have both installed a solar panel system on a flat roof. So we can compare the cost of the entire system (including the inverter, standards, mounting hardware, wiring, installation and additional group in the fuse box) after 5 years. So I have reference material to compare the prices of solar panels (with my personal experience), which are nearly halved since 2010:
With the App Solar ROI (only for iPhone/iPad), we calculated the payback period of solar panels and concluded that his investment was returned within seven years.