As you know in grid-tied connection the PV system is connected to the national grid. Armenian regulation allows to sell the excess electricity to the grid at the half-tariff. Taking this into account the majority of “autonomous producers” (consumers who have switched to solar electricity to cover their needs) wants to install more powerful systems than they need, in order to make some revenue by selling electricity. But before investing (paying for a PV station) the payback period must be calculated.