A simple grid-tied PV system generates and sends electricity directly to your home's electric panel. If you can't use all the electricity immediately, your system sends the extra to your local utility.
Grid-tied systems have the lowest initial cost because they have the fewest components. Fewer components also means greater system efficiency. The main drawback to a simple grid-tied system is that when you lose utility power, your inverter shuts down, and you can't generate power for your own use even if the sun is shining.
Utilities require a signed net metering agreement before you're allowed to connect to their grid. This agreement covers maintenance and reporting responsibilities. Most utilities credit your account at full retail rate for the power you send them and bill you only for the power you use above what your system has produced. Credits roll over month to month and are zeroed out periodically.
Because net metering agreements are subject to change by Public Service/Utilities Commissions, check your state's most current rules regarding how long your credits will roll over and what the reimbursement rate is for the power you generate.