Grid-tie systems depend on a local or regional electrical grid to replace the function of batteries in an independent system. The power that is produced is continuously fed into the grid and power consumption is not constrained by generation rate since peak power demands are satisfied by the grid. In grid-tie systems, the owner is allowed full retail value for the energy produced. These systems must conform approximately to the existing demand. Historically in Costa Rica, excess power generation was credited for future use. Now, modest excess production is compensated with payment for the power, within limits.