Solar Enquiry Form
FAQ: Grid Connected Solar Rooftop System
Solar On Grid Solutions FAQs
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.
Cost of System and Subsidies
The current benchmark cost of grid connected rooftop solar systems can be seen in notification section at
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 selfgenerated. 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.
Metering Arrangement for Solar Rooftop
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 predecided 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.
Business Model for Solar Rooftop System
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
Installation of Solar Rooftop System
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.
