A solar system does not only work at maximum capacity. In low light conditions such as early in the morning or when it is overcast, solar panels will still convert light into power for your home, just at a reduced rate.
For example, a 5kW system may only be outputting 2kWs of power on a cloudy day. There is a point where the energy produced is no longer strong enough to power the inverter and the system will turn off. This happens every evening and perhaps during an especially dark storm.
Here is an example of one of our high performing Enphase Micro Inverter systems on an overcast day. As you can see output can change minute by minute as the sun comes out and disappears again behind the clouds. This system is orientated just west of north so the peak solar output occurs from late morning through to around 4 pm in the afternoon. This is an early spring day (September) so the peak output period will increase in length over summer, and be a little shorter in winter.