This depends on how your system is designed.
Each households electricity consumption, home's solar radiation and home's roof space varies!
A customized quote can be provided to offset nearly any percentage of your estimated consumption.
There is no right amount of panels to put on your home. You can choose to offset 100%, or 50%, but you will receive a similar percentage return on investment for both.
It is all relative to the unique conditions of your home, and the amount of money you'd like to invest into a P.V. System.
If there is any reason you anticipate more consumption, for example purchasing an electric vehicle, or adding A.C. to your home, additional panels can be built into your installation to accommodate for this.
You can also select to offset just a portion of your consumption.
It all depends on your goals and budget for your solar project!