It certainly contributes but the overall design is more complicated than that. My location is fixed, my days of sunlight are reasonably well known, so calculating the output is not difficult.
Where the additional cost for the initial investment comes in are things like battery sizing, location vs distance to batteries, inverters, control panels, etc. Does one create enough energy to only offset some of my electricity? Would two units take me off grid or would I have to get three?
It is a spreadsheet exercise that I need to look into.
Compass orientation and verticle angle are critical to getting optimum output from panels.
Have you tried a small PV test panel in your location? People are always surprised when they get far less than rated max output from panels.
Good luck.