A word of caution to all.
Check the power input rating of your inverter charge controller and, after taking into account the thermal derating factor, make sure your solar panel output does not exceed this. I differ a bit from others inasmuch I apply a derating of 10% which gives me a fair margin that I happen to be comfortable with.
The worst case conditions are:
1. New panels.
2. Spotlessly clean.
3. Sunlight perpendicular to the surface of the panels.
4. A goodly breeze to waft some of the heat away from the panels.
Another very important point is to make sure that your maximum panel string* voltage (Voc) does not exceed the maximum permitted input voltage of the inverter charge controller. If it does, damage will occur and you will get some of @Crossy magic smoke.
Solar panels will loose 1%/annum of their rated output so after 20 years your output will be down to 80% of new.
There are some new techniques which improve on both the maximum output and longevity (25 years) but the regular panels are still at around 20% output which is to say that if 1kW of sunlight is shinning perpendicular to a 1 metre² panel, the panel will produce 200W of power.
* A string of panels is a number of panels connected in series so that their voltages are summed.