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FAQ – For Solar Power

What is a Solar Rooftop System?

In a solar rooftop system, the solar panels are installed in the roof of any residential,
institutional, social, Government, commercial, industrial buildings etc.. This can be of two

  • Solar Rooftop System with storage facility using battery
  • Grid Connected Solar Rooftop System.
What is a Grid Connected Solar Rooftop System?

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

What are the main components?

Solar PV Modules/Solar Panels – The Solar PV modules/Solar Panels convert solar
energy to electrical energy. They are available in different technologies such as
crystalline, thin film, CIGS, CdTe, HIT, etc. Crystalline Solar PV panels are most
common in use on roof tops.

  • Inverter : Inverter converts DC output of Solar PV panels into AC power.
  • Mounting structure : The mounting structure, is the support structure that holds the
    Solar PV panels.
  • Balance of System : These consist of cables, switchboards, junction boxes, meters,
    structures, tracking system (if required), earthing system ,circuit breaker,fuses etc.
What are the models for implementation of Rooftop PV systems?
  • CAPEX Model : Here, the entire system is owned by the rooftop owners and he bears the cost of the Soalr system. Responsibility of O&M for the system lifetime (25 years) is also with the rooftop owner. Developer is responsible for installing the system and initial 2 years O&M and five years warranty.
  • RESCO Model : Here, the entire system is owned by the developer. Responsibility of O&M for the system lifetime (say about 25 years) is also with the developer. Rooftop owners may consume the electricity generated, for which they have to pay a pre-decided tariff on a monthly basis. Excess generation may be exported to the grid, subject to availability of requisite state regulations.
Which model is best for me?
For consumers that have adequate manpower/expertise for O&M, rooftop access concerns, availability of funds upfront, CAPEX model is better. Consumers in states that have netmetering regulations can take benefit of the same in case they have substantial excess generation. On the other hand, consumers who prefer not to take responsibility for the system O&M, do not have rooftop security concerns and prefer to pay on a monthly basis rather than bulk upfront payment may choose to go for RESCO model.
What is net-metering?
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.
What is Gross Metering?
In gross metering the energy generated from the spv plant is feed to the grid . In lieu to the energy fed to the grid , they are paid a feed in tariff.
How much area is required for a 1 kW rooftop Solar PV system?
A 1 kW rooftop system generally requires 10 sq. meters of shadow-free area. Actual sizing, however, depends on local factors of solar radiation and weather conditions, efficiency of solar module, shape of the roof etc. If you are using latest high technology modules like Mono PERC then required area can significantly reduced.
What is the minimum warranted period envisaged under the scheme?
Solar PV modules used in solar power plants /systems must be warranted for their output peak watt capacity, which should not be less than 90% at the end of 12 years and 80% at the end of 25 years. The mechanical structures, electrical works including power conditioners/inverters/charge controllers/maximum power point tracker units/distribution boards/digital meters/switch gear/storage batteries, etc. and over all workmanship of the SPV power plants/ systems must be warranted against any manufacturing/ design/ installation defects for a minimum period of 5 years.
What are the other fiscal incentives are available for Solar Rooftop Systems?
There are provisions of concessional import duty, accelerated depreciation, tax holiday for setting up grid connected rooftop power plants.
Kindly name the States having notified the solar rooftop policy?
Please see the details in website . Amendments if any may kindly be seen at the respective websites of the State Renewable Energy Department.