Solar shadowing is like blocking a water pipe. If one cell is fully shadowed, it does not just block current through that cell, it blocks the entire string. Because of this, only a few shadowed cells can block your total solar output. If partially shadowed, (e.g. by light cloud) the loss is proportional to the amount of sunlight being blocked. The higher quality solar modules produce some output unless clouding is severe. It is, however, rare to have zero during ‘daylight hours’.
Top quality solar modules for homes and properties catch 18% to 20% of the solar energy available. This is typically 140 watts-180 watts per square metre in full sun from about 10 am to 2 pm. Input tapes off before and after. The most efficient are priced accordingly.