In a solar rooftop system, the solar panels are installed on the roof of any residential, commercial, institutional and industrial building.

A 1 kw rooftop system generally requires 7.5 sq. metres (80 square feet) of flat, shadow-free area (preferably south-facing). Actual sizing, however, depends also on local factors of solar radiation and weather conditions and shape of the roof.

These are two types:
(i) Solar Rooftop System with storage facility using battery
(ii) Grid Connected Solar Rooftop System

The grid connected rooftop system can work on net metering basis wherein the beneficiary pays to the utility on net meter reading basis only. Alternatively two meters can also be installed to measure the export and import of power separately. The mechanism based on gross metering at mutually agreed tariff can also be adopted.

It depends on the consumption cycle. If the consumption cycle matches with the generation cycle then battery may not be required. Also, in case of net metering, excess power will be credited in the bill so no battery is required.

Solar panels manufacturer’s warranty is 25 years. So, broadly life of solar rooftop is 25 years. However, it does function after 25 years with 80% output.

Solar panels work just fine in ambient light and will produce significant energy in the fog or on overcast days. In bad weather, the production may not be 100% but they will produce power. On cloudy days, they may produce 60% of the required output. Germany, who ranks low in sunny days, is the solar energy capital of the world.

They rarely require any  maintenance or cleaning, plus they have warranty of minimum 25 years. All it  requires is to clean panels once every 20-25 days with a cloth.

Subsidies are available from multiple channels for setting up  Rooftop PV projects.

Subsidy / Support from Central Government through MNRE. Government Institutions including Public Sector Undertaking (PSU) shall not be eligible for subsidy; instead they will be given achievement-linked incentives / awards. Subsidy / Support from State Government through State Nodal Agencies (SNAs): Subsidy support is also available in various states. The percentage of subsidy varies according to the state policies.

(a) Reduce water usage
(b) Reducing air pollution
(c) Help in mitigating climate changes