Your solar PV system only produces when the sun is out, with the majority of the production occurring during a 4-6 hour window. So in order to offset ALL your usage, you will likely need to overproduce during the day to compensate for the power you use when the sun is not shining. This is where net metering comes in.
Net metering is the tracking and compensating of the power your solar PV system sends back to the grid.
Net metering acts as a more affordable battery, where instead of storing the excess power, the utility company will send it to someone else who can use it immediately, and compensates you for the overproduction.
The best utilities offer a 1 to 1, meaning, for each kWh you send them, you get a full kWk in return. More common is some kind of reduced rate. So in Utah, the average cost is 13¢/kWh, and the net metered rate is about 6¢/kWh - not bad, and still more cost effective than a battery.
If you live in an area with NO net metering, that doesn't mean solar is bad. You might either have to size your system for your daytime usage OR get a battery to cover your nighttime needs.
For more details on net metering and different state policies, click here.