A roof that does a little more
Solar panels turn daylight into electricity. An inverter changes that electricity into a form your home can use. When the system is producing power and your home needs it, some of that demand can be met from your roof.
Your home still has a relationship with the grid
At times, your panels may produce more than your home needs. At others, you may need more than they produce. Your connection rules, electricity plan, and equipment determine what happens next. Ask how imported and exported energy are measured and valued on your actual tariff.
Size is a starting point, not the whole story
A system’s rated size and its real output are different things. Roof orientation, shade, weather, temperature, and installation design all affect production. A proposal should explain its estimate and the assumptions behind it.
The better question
Instead of asking for the biggest system you can fit, ask what design makes sense for your home. Bring your recent electricity bills and mention changes you expect, such as an electric vehicle or working from home more often.
Further reading: U.S. Department of Energy: Homeowner’s Guide to Solar. Local rules and individual circumstances vary. This guide is general information, not a quote or financial advice.