Frequently Asked Questions

In grid connected rooftop or small solar photovoltaic (SPV) system, the DC power generated from solar panel is converted to AC power using power conditioning unit/Inverter and is fed to the grid. Operating modes of grid connected rooftop solar PV system can be explained

• Solar PV Modules/Solar Panels – The Solar PV modules/Solar Panels convert solar energy to DC (direct current) electrical energy. They are available in different technologies such as crystalline silicon, thin film silicon, CIGS, CdTe, HIT, etc. Crystalline Silicon Solar PV panels are most commonly used in solar. rooftop system. Multiple panels are connected together to form arrays as per the desired capacity of the system.
• Inverter – Inverter converts variable DC output of Solar PV panels into AC power. Inverter also synchronizes with the grid so that generated power from the module can be injected into the grid.
• Module mounting structure – The module mounting structure, is the support structure that holds the Solar PV panels in place for full system life and is exposed to all weather conditions. These are normally fixed at particular angle and orientation in case of solar rooftop system. But these can also be of type that tracks the Sun, called as trackers.
• Bi-direction Meters – Meters are used to record the generation or consumption of electricity. Bi-direction (or Net-Meters) are used to keep track of the electricity that solar PV system injects to utility grid and the electricity that is drawn from the utility grid.
• Balance of System – These consist of cables, switchboards, junction boxes, earthing system, circuit breaker, fuses, lightning protection system, etc.

A 1 kW rooftop system generally requires 10 sq. metres of shadow-free area. However, actual area requirement may vary depending on the efficiency of solar module, and their placement etc

Solar modules (and cells within) need uninterrupted sunlight to produce maximum electrical energy. With the shadow even on a part of the module, the generation reduces to a great extent thereby wasting installed system capacity. Also, prolonged
(regular, though intermittent) shadow on some cells or modules reduces their life substantially and these become useless much before their standard life of over 25 years.

Rooftop solar PV systems can be installed on any type of roof having sufficient load bearing capacity. .

On a clear sunny day, 1 kWp solar power plant can generate 4 to 5.5 units in a day.

No, the daily energy generation from the RTS shall be dependent on the temperature and solar irradiance among other parameters and these may not be same every day

• Plant Location
• Quality of equipment used
• No. of sunshine hours
• Workmanship
• PV module tilt angle and orientation
• Module Cleaning
• O&M activities etc.

No. On exposure to sunlight and outside environment, the solar module lose their generation capacity and this is called degradation.

• Saving on electricity bill by the consumer.
• Utilization of available vacant roof space, no additional land required.
• Low gestation period.
• No additional requirement of transmission and distribution (T&D) lines.
• Reduces T&D losses as power consumption and generation are collocated.
• Improvement in the tail-end grid voltages and reduction of system congestion.
• Long term energy and ecological security by reduction in carbon emission.
• Better management of daytime peak loads by DISCOM/ utility.
• Meeting of the Renewable Purchase Obligations (RPOs) of obligated entities.

The current benchmark cost of grid connected rooftop solar systems can be seen in notification section at https://solarrooftop.gov.in/notifications/view

Central financial assistance (or subsidy) is available only for residential sector grid connected solar rooftop projects only. For other sectors e.g. Govt., institutional, social, commercial, industrial etc. CFA is not available. Central Financial Assistance (CFA)* to Residential sector

• CFA @ 40% of benchmark cost or @40 % of tendered rates (whichever is lower) for capacity up to 3 kWp
• CFA @ 20% of benchmark cost or 20 % of tendered rates (whichever is lower) for capacity beyond 3 kWp and up to 10 kWp
• CFA @ 20% of benchmark cost or @ 20 of tendered rates (whichever is lower) for GHS/RWA capacity up to 500 kWp (limited to 10 kWp per house and total upto 500 kWp)

For calculation of CFA, the PV plant capacity will be inverter capacity or the PV module capacity, whichever is lower. For availing CFA, the PV module and cell shall be manufactured in India only.

No. Consumer has to pay the balance amount after deducting the subsidy (eligible CFA) from the L1 project cost discovered by the DISCOMs. Advisory on scheme is also available at https://mnre.gov.in/img/documents/uploads/file_f1610949591054.pdf

Consumers are advised to pay only according to the rates (L1 rates) decided by DISCOMs. If any vendors are charging more price than the rates decided by DISCOMs from domestic consumers, in that case consumers are advised to inform DISCOM so that the DISCOM identify and punish such vendors.

Information on state subsidies can be seen on the website of the concerned electricity distribution company. The rooftop solar portals of electricity distribution companies can be assessed at: https://solarrooftop.gov.in/grid_others/discomPortalLink

No. MNRE is implementing the programme through power distribution companies/DISCOMs of various States. These DISCOMS are responsible for discovery of rates and empanelment of vendors for implementation of the projects..
Consumers can apply online through the portals of these DISCOMS which can be assessed at: https://solarrooftop.gov.in/grid_others/discomPortalLink

The system price, though important, should never be the only factor for deciding vendor. Customer should consider at least the following factors:

• Price of the offered system.
• Warranties of system and components.
• Energy generation estimates and guaranties.
• Service backup and arrangements the vendor has in the area.
• Reference installations in the track record of the vendor – along with those customers’ feedback about system performance and service provided by the
  vendor

Since the system is grid connected through net metering, DISCOM will generate bill based upon the reading provided by the net meter installed at the consumer premises. The consumer will have to pay for the net units (total imported units minus exported solar units) only

This is possible in very rare cases because the consumer shall be required to pay some minimum charges like fixed charges, etc. even if the consumed energy is all self-generated. However, ‘electricity charges’, a major component of the monthly bill, can be reduced to zero by optimally designing and maintaining the RTS. The monthly electricity bill may come to zero in States which give revenue for surplus power generated.

All solar PV systems generate power only during daytime when sun is available. In net metered systems, the generated power is utilized for self-consumption, and excess power is exported to the grid as long as grid is available. In case, where solar power is not sufficient due to cloud cover etc., power is drawn from the grid to power the loads. A bi-directional or net meter records the energy flow in both the directions and at the end of billing period net energy used is calculated. The beneficiary has to pay for only the net energy used.

In gross metering the power generated from the Rooftop Solar plant is only fed to the grid. The system owner gets paid by the DISCOM for such exported power at a pre-decided tariff

Connections in net billing RTS are similar to net metering. However, at the end of the billing cycle (normally a month) any excess energy in the grid shall not be carried forward like in net metering, but shall be purchased by the DISCOM as per pre decided tariff. Therefore, energy banking in the grid is only within a billing cycle.

Yes, the plants which are not connected to the grid are normally called behind the meter plants and MNRE subsidy is not available for such plants even for residential sector. However, it is required to follow rules and regulations specified for this purpose by the state authorities.

CAPEX Model: Here, the system is owned by the consumer himself and he bears the cost of the system.

RESCO Model: Here, the entire system is owned by the 3rd party project developer. The consumer only purchases the generated energy by paying pre-decided tariff on a monthly basis as per Power Purchase Agreement (PPA). Responsibility of O&M for the system lifetime (25 years) is also with the developer.

A simple payback period can be calculated by using rooftop calculator available at following web link: https://solarrooftop.gov.in/rooftop_calculator

Residential consumers and Group Housing Society can apply for installation of solar rooftop system through the online portal of DISCOMs. The link for the online portal of DISCOMs is mentioned https://solarrooftop.gov.in/grid_others/discomPortalLink

The interested beneficiary may install the solar rooftop systems through project developers/system integrators/manufactures etc. after taking necessary approval from DISCOMs within the capacity limit as laid down in the order of respective State Electricity Regulatory Commission/Joint Electricity Regulatory Commission of the respective States/UTs.

The RTS under any framework like net or gross metering can be installed by the electricity consumer. So, if you have electricity connection in your name and you pay regularly the electricity bill in your own name and also you have the permission of use the roof for solar rooftop installation from the owner, you can install the RTS

With several common rooftops available in a society, there is a great potential for harnessing solar energy through rooftop PV systems. The energy generated from these systems is used to offset the common loads of the society (common lighting, lift, pumps, etc.). A Net Meter shall be provided against, the Single Point Delivery (SPD) common meter of Cooperative Group Housing Society (CGHS). In this, the society ultimately gets benefitted in terms of reduced monthly electricity expenses.

The system is easy to be dismantled and reassembled elsewhere. So, it can be shifted to your new residence

Yes. Only indigenously manufactured PV modules with indigenous solar cell can be used in Solar PV systems power plants for subsidised sector projects. For reference, as per the ALMM list 10th March 2021 Clause 4 IV- Link:-(https://mnre.gov.in/img/documents/uploads/file_f-1615380939218.pdf). However, there is no such limitation in case the project installed without any subsidy.

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 overall workmanship of the SPV power plants/ systems must be warranted against any manufacturing/ design/ installation defects for a minimum period of 5 years

Compared to most other power generating technologies, solar PV systems have very low maintenance and servicing requirements. However, suitable maintenance of a PV plant is essential to optimise energy yield and maximise the life of the system. Some of the maintenance activities typically may include but not limited to the following:

Module cleaning is required periodically (dust, bird dropping and other debris can cause decrease in power generation). Periodicity depends on local conditions like dust, birds, air pollution, etc.

Other items should be checked periodically as stated below:

• Checking module connection integrity
• Checking junction boxes / string combiner boxes
• Inspecting mechanical integrity of mounting structures
• Tightening cable connections that have loosened
• Replacing blown fuses
• Repairing lightning damage
• Repairing equipment damaged by intruders or during module cleaning

The solar modules are made up of toughened or tempered glass top and so are not easily broken due to monkeys or any falling objects. These can be broken if deliberately someone throws stones. Guarding of module surface with wire mesh is one solution for monkey menace, but not recommended because this regularly casts shadow on the modules.