Grid-connected photovoltaic system is one of the simpliest ways to use solar power, and depending on the setup, it can easily generate enough power to cover its costs. A grid-connected doesn't require batteries, so it has no storage losses. You use the power immediately as you generate it.

If the system falls short of needed power, because it is 'grid-connected', the traditional electric grid is used to cover the remaining usage. This means you don't have to build a system that will cover your entire house usage, you can start small and reduce your power bill proportionately.

If the system generate more power than is consumed, you can often sell that power into the grid itself and get paid for it, depending on your local power configuration, ask your power company for more details.