In a solar rooftop system, the solar panels are installed in the roof of any residential, commercial, institutional and industrial buildings.
This can be of two types
(i) Solar Rooftop System with storage facility using battery, and
(ii) Grid Connected Solar Rooftop System

Such rooftop system has battery as storage facility. The solar electricity is stored in the battery and can be utilized during night also when the sun is not available.

In grid connected rooftop or small SPV system, the DC power generated from SPV panel is converted to AC power using power conditioning unit and is fed to the grid either of 33 kV/11 kV three phase lines or of 440/220 Volt three/single phase line depending on the capacity of the system installed at institution/commercial establishment or residential complex and the regulatory framework specified for respective States.

These systems generate power during the day time which is utilized fully by powering captive loads and feed excess power to the grid as long as grid is available. In case, where solar power is not sufficient due to cloud cover etc., the captive loads are served by drawing power from the grid.

Such rooftop systems can be installed at the roofs of residential and commercial complex, housing societies, community centers, government organizations, private institutions etc.

There are provisions of concessional import duty/excise duty exemption, accelerated depreciation and tax holiday for setting up of grid connected rooftop power plants.

The rooftop solar systems from 1 kWp upto 500 kWp or in combination can be set up on the roofs.

About 12 sq.m area is required to set up 1 kWp grid connected rooftop solar system.

According to India Meteorological department, Rajasthan has 320 Days of 5-7 sun hours. We take 300 days to for the sake of calculation and expect average generation of 5 units per day by a system of 1KWp grid connected solar system.
Annual Generation = 5 units X 300 days = 1500 units/KWp

The land required for a 1 MW power plant setup is around 4.5-5 acres for Crystalline technology. This is only a rough benchmark and may vary based on technology and efficiency of panels.

The useful life of a typical Solar Power plant is considered to be 25 years. This is the duration for which long-term PPAs are signed and financial models are built. However, Solar Power plants can run beyond 25 years while producing a lower output. Many Solar Panel manufacturers guarantee an output of 90% at the end of 10 years and 80% at the end of 25 years.

Total project cost per MW would be in the range of Rs.6.5 Crores.

There is no subsidy available for utility-scale SPV plants. Various states offer a bouquet of incentives (such as exemption from Open Access charges, feed-in tariffs, tax benefits, accelerated depreciation etc.) to solar power projects that are set up under their state schemes.