This is done by means of softwares that are specifically developed for energy and power systems.
PVSyst is the industry’s most credible software in simulating solar system. It’s not a free software, but is widely used by many companies in the industry to carry out their design work. It may need a bit of introductory knowledge from the user before being able to run a full simulation.
RETScreen, which is developed by the Natural Resources Canada and is available for free, can be used for preliminary purposes of design work.
In general in southern Ontario, you can assume that your system will generate around 1,100 to 1,200 kWh of electricity per kW of system installed, in a year.
For example if you have a 5.5kW DC system, then system annual generation will be:
5.5 x 1,100 = 6,050 kWh in the first year.