The advantage of adopting rooftop solar is received in terms of potential savings through lower electricity bills. Added benefit from adopting rooftop solar is the possibility of utilising a renewable source of energy (solar) which results in reduction of carbon emission.

With the target set for 450GW by 2030, the Government of India is encouraging adoption of solar energy. The present status for financing a Solar Rooftop project consists of CAPEX and RESCO model. The CAPEX model allows the customer to either pay 100% upfront or take up a loan where the customer must make regular payments to the bank at a rate of interest. In the RESCO model a third party company finances, installs, operates and maintains the rooftop solar installation. An agreement is reached between the third party and customer for the consumption of generated solar energy. The RESCO model offers savings as the solar energy tariff is usually lower than the grid energy tariff. However, the CAPEX model has the benefit for customers to own the system and usually offers lower tariffs as compared to the RESCO model.

The generation of electricity through solar energy offers the customer a cheap source of energy and contributes to the transition of electricity generation to renewable energy sources. Having rooftop solar installed at your property offers a higher value to the property for the reasons mentioned above (Monetary savings and Emission savings). However, the influence of rooftop solar on your property usually depends on factors such as the cost of grid-connected tariff in the area, and the size and lifetime of the installed system.

Generation of electricity using rooftop solar allows for in-house consumption of electricity and potential revenue in the case when excess is exported to the grid. To be able to account for the consumption from rooftop solar, grid and export of excess to the grid; different metering mechanisms (e.g.: Net metering, Gross metering) are employed. The detailed account for the consumption and export is shared with the customer through a billing statement depending on the billing cycle of respective states.

One of the critical aspects of utilising the rooftop solar system is the upkeep of the operation and maintenance activities. The activities range from supervising operation related parameters for optimum generation of electricity to replacement of spares and maintaining a cleaning schedule. There are multiple models that can be employed for operation and maintenance of the system, such as self-O&M, where the owner takes the responsibility to maintain the installed system. Another option could be contracting the operation and maintenance of the solar system to an external company, based on the terms of agreement. According to CERC, the O&M cost can be estimated to be 1.4% of the capital cost for the first year with an annual increase of 3.84% from the second year (this is subject to change with annual revision).

The benefit to customers is provided through subsidies and incentives. However, the subsidy for grid-connected solar systems is only available for the residential homes (https://mnre.gov.in/solar/schemes). The Government of India and relevant state bodies have offered various subsidies for group housing and installation of solar parks. The industrial and commercial sector enjoys various incentives such as tax benefits, accelerated depreciation, excise duty exemptions.

The Solar savings are incurred usually by replacing or reducing use of grid power by the solar system. The potential of savings depends on multiple variables such as size, tariff, cost of equipment, O&M cost etc. Thorough analysis of PV systems and/or Battery systems can provide the customer with an option to have potential savings on the electricity bill. Few economic indicators to gauge the financial benefit of the investment are Payback period, Return on Investment, Net Present Value of the investment. The application Solsavi provides an opportunity for the customer to enter relevant information (load profile, tariff details, investment details,…) and receive an optimally suggested solar panel and Battery system based on financial analysis.

A rooftop solar installation consists of a solar panel, inverter &/or battery system with relevant supporting components and systems of the power plant. The major investment would be the initial investment for the rooftop solar system. As the solar system is a solid state technology, no moving parts are available and hence lower wear and tear of equipment. However, regular operation and maintenance charges are applicable to upkeep the system to maximum efficiency. The cost for generating solar energy from rooftop installation in India is estimated to be $66/MWh (approx ₹ 5000/MWh) as compared to China ($68/MWh).

Solar Photovoltaics (Photovoltaic stands for photo, meaning ‘’light’’ and voltaic meaning ‘’electricity’’) utilises the principle of Photoelectric effect to produce electricity. The Solar panels convert sunlight to DC (direct current) electrical energy. Solar panels are made of semiconductor materials, which when exposed to sunlight produce a small amount of electricity. To produce a large amount of energy from the solar panels, they are placed in combinations which are called arrays. Solar panels are an assembly of photovoltaic cells mounted on a frame. Solar photovoltaic cells are made up of semiconductor materials, these materials generate electricity when exposed to light of particular wavelength. The efficiency of a photovoltaic cell depends on the semiconductor material used. Some common materials used for photovoltaic cell fabrication include Silicon(Si), Cadmium Telluride (CdTe), Copper Indium Gallium Selenide (CIGS) or Gallium Arsenide (GaAs).

The process spans from finding a suitable solar developer, analysing the consumption, selecting the appropriate solar (& battery – for storage of solar generated energy) size, Selecting the auxiliary equipments (such as inverter or hybrid inverter – in case battery storage is adopted), Procure relevant clearances from the local Nodal Agency, collecting quote for various purchase and installation of the system, Evaluating site & finance feasibility to Execution of the activity.

It depends on multiple factors including size of the solar system to be installed. The application and installation of a special meter for tracking generation and consumption also adds to the period of installation of the solar system.

In a grid-connected rooftop or small solar photovoltaic (SPV) system, the power generated from the solar panel must be altered to be able to use the power to operate appliances. This is achieved through a power conditioning equipment called Inverter, which converts the DC power generated from solar to AC power. Solar panel systems generate power during sunshine hours and can export solar power to the grid. Consumers with grid connected solar systems can self-consume solar energy that is generated, export surplus solar energy to the grid and import energy from the grid when required.

Alternating current, abbreviation AC, flow of electric charge that periodically reverses. It starts, say, from zero, grows to a maximum, decreases to zero, reverses, reaches a maximum in the opposite direction, returns again to the original value, and repeats this cycle indefinitely. Direct current, abbreviation DC, flow of electric charge that does not change direction. Direct current is produced by batteries, fuel cells, rectifiers, and generators with commutators

The solar system will be functional, however there would be low generation in shadow, cloudy days, rain or due to dust accumulation and no generation of power at night. Solar panels produce power only when exposed to light of specific wavelengths. Hence, anything that reduces the exposure of the panel to light will lead to reduction in the generation capacity of the panel.

The solar panel is covered by a protective cover that safeguards the solar panel from any rain or snow. However, in case of hail storm, the protective cover could be damaged and must be replaced. Electrical equipment must be protected from exposure to rain and snow to prevent damage.

Grid connected rooftop solar systems offer the customer an option to consume energy generated by renewable resources. Solar energy is available only during sunshine hours. Hence, if the power outage occurs during non-sunshine hours then the rooftop solar system would require a battery storage to act as a back-up source of energy.

Solar panels are capable of generating electricity only in the presence of direct sunlight and will not be able to generate during night time. Therefore, if the user wants to use the solar energy generated by the solar panel during daytime, then solar energy must be stored for later use. One of the most common methods of saving electricity is making use of battery storage systems, which store the excess (electricity units more than self consumption) generated from solar panels. The advantage of Solar panels plus battery systems offers reduced dependency on grid power, leading to savings from reduction in electricity bills.


Solar panels are responsible for generating electricity using the sun light. The use of solar panels allows the user to produce and use the electricity generated instead of grid connected electricity, leading to lower dependence on electricity from grid and monetary savings. During a particular time frame if the electricity generated by the solar panels is more than the units required (self consumption), the excess electricity generated can be stored in batteries for later use or the excess electricity generated can be sold to the respective DISCOMs at the predetermined rate determined by the Nodal agency. Every state has determined the compensation rate for the electricity sold back to the DISCOMs.


About 10 m2 of shade free area is required to set up a 1 kW grid connected rooftop solar system.


The primary component of a rooftop solar installation consists of a) Solar panels (to generate energy) b) Inverter ( to convert the generated DC current to AC current) c) Mounting system, cables, fuses, switchgears, etc ( Balance of system ) and if required d) battery system ( to store energy for later use). It is advised that the solar installation is done by approved and experienced personnel to avoid any mishaps to either the user or the equipment


Yes, the installed equipment and auxiliaries that comprises the part of the rooftop system can be disassembled and reassembled at another location. However, care must be taken before and during installation such that the activity does not damage the equipment. If the rooftop system is shifted to a new location, the consideration for the location feasibility must be reviewed along with any change in tariff or regulations.



A Solar PV system generally weighs 15 to 20 kg per square meter. This weight can be easily borne by most roofs. Since the life of a Solar panel system is about 25 years , do ensure that your roof is in good condition to bear the system’s load over its lifetime.


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Yes, you will need to replace it with bi-directional meter. For solar net metering and solar net feed-in, your electricity meter needs to record and display bi-directional energy flows (import and export). Usually, the energy meter are only programmed to record and display unidirectional energy flow (that is, import). When installing a rooftop solar system, they need to be replaced with bi-directional meter.


Yes, A solar panel can be installed at the site even if the user has a government provided electricity connection. The solar panel can be used to generate electricity either for self-consumption or direct sale to respective agencies.


Although there is no clear indication for the number of fires caused in a rooftop solar installation, a solar system bursting into flames is a very rare occurrence. However, the operation of rooftop solar systems must be evaluated for the existing risks with respect to the location of the installation. The risks associated with rooftop solar can include injuries from sharp edges, working with hot surfaces and include fire risks that can lead to hazard for human personnel as well as equipment damage. Hence, a thorough risk assessment must be included before installation of rooftop solar.


The ideal location for the best performance of a solar panel depends on variables such as orientation & tilt of the solar panel, availability of shadow-free area & cleaning and maintenance of the solar panel to name a few. The parameters are relative to the selected location for installation and hence suitable location for installation must be selected.


Solar energy generation depends on a variety of factors such as plant location, season, module efficiency, maintenance etc. but as a rule of thumb you can generate up to 4.5 kWh per day for a 1kW solar system.


There are multiple factors that influence the efficient performance of rooftop solar some of them are as follows (however, not restricted to the below list):
● Plant location
● Solar system design (including PV module tilt)
● Equipment quality
● Shading
● Maintenance (cleaning of panels)

To be able to effectively use the solar radiation for electricity generation using solar panels, the solar panels must be exposed to direct sunlight. To ensure optimum performance from solar panels , continual cleaning and maintenance is necessary. Therefore, regular cleaning of the panels is recommended and advised. However, the method of cleaning the panels can be decided by the user. The user can decide to either manually clean the panels or employ an automated system to maintain the panels. It must be noted that any decision taken with respect to maintenance of the panels must be added to the Operation and Maintenance cost of the system.


Yes, the installation of future devices/equipment can be accommodated. However, the use of high power consumption devices leads to consumption of higher units as compared to the average units consumed. The previous installation would have to be revisited to be able to accommodate the new load. Nonetheless, if the user does not desire to make a change; the installed system could continue to reduce the electricity bill as compared to a situation without an installed system.


Solar PV is a highly proven and reliable technology. A well-designed, installed, and maintained system will operate for 25 years or longer. The inverters may need a replacement after 10 to 12 years. Moreover, since there are no moving parts, there is practically negligible wear and tear for your solar system.

No. Solar panels reduce their generation capacity over time – degradation. The solar energy output will reduce between 0.3% to 1.5% per year.

Solar systems are highly reliable if designed well. Moreover, the key components of a solar system are backed by guarantees & warranties. However, it is advisable to buy an insurance cover for your solar system.

For grid-interactive solar systems, certain approvals are required. These approvals usually vary from state to state and for respective system sizes. Permits and approvals typically required are: Interconnection permission from your power distribution company. Safety certificate from the Chief Electrical Inspector to the Government of state for solar systems above a certain size (10 kW and above in the case of Tamil Nadu).

The installation procedure for industrial and commercial consumers does not vary in regard to acquiring the connection and permission for installation. However, the grid tariff varies for the industrial and commercial consumers and this influences the economic feasibility of the installation.

In the case the installed PV system is generating electricity above the load requirement during sunshine hours, the excess solar generation can either be stored in a battery storage system for later use or it can be exported to the grid to earn credits of units (kWh) or revenue depending on the adopted metering mechanism.

There are multiple metering mechanisms that can be used for energy accounting of a system that has a rooftop solar installation (redirect to blog). The availability of the metering mechanism depends on the respective state policy with regard to grid connected rooftop solar. The metering mechanism is used to account for the energy consumed and generated using the installed system. Net metering, Gross metering & Net feed-in are some of the common metering mechanisms employed around various states in India.

This means when your solar energy system produces more electricity than your home needs, the excess electricity is sent to the power grid and your utility pays you for it. Net metering is what makes rooftop solar panels such a great way to save money.
Solar net metering allows you to feed any surplus solar energy generation into the electric grid, and in return receive credits on your electricity bill. Essentially, surplus solar energy exported by you to the grid is compensated at the tariff that you pay to your electricity utility for import of grid energy. The availability of net-metering varies depending on the solar policy of your state.

Along with the installation of grid connected rooftop solar, the energy consumed and exported – in case of excess generation – must be accounted for, to determine the remuneration at the end of the settlement period. There are bi-directional meter employed to account for the imported and exported units for a billing period. The number of meter required depends on the metering mechanism adopted by the consumer. For e.g. in gross metering, the consumer would have to install two meter to account for imported and exported units separately.

Feed-in tariffs are a compensation scheme which offers guaranteed cash payments to producers of energy, based on an established rate per kWh. The rate of compensation established under FITs is often higher than the retail rate, and the payments are typically guaranteed through a long-term contract. Solar net metering allows you to feed any surplus solar energy generation into the electric grid. However, unlike solar net metering, this surplus energy exported is compensated at a fixed predetermined feed-in tariff, independent of your electricity tariff.

Gross metering is a mechanism in which the entire energy generated by your solar system is exported to t3he grid at a certain predetermined tariff (INR/kWh). Some states, such as Karnataka, allow a choice between net metering and gross metering.

The provision to switch between metering mechanisms is not dynamic or flexible. The procedure would involve submission of application for the desired metering mechanism and settlement of previous metering mechanism before switching to the desired mechanism. There can also be a possibility where the configuration for energy accounting also must be modified with the selected metering mechanism (installation of more meter). Hence, the switching between metering mechanisms would be similar to approaching the department for a new connection.

High Tension (HT) consumers means a consumer who is supplied with electricity at a voltage of 440V and above.

Low Tension (LT) consumers means a consumer who is supplied with electricity at a voltage below 440V.

For many consumer categories, solar energy today is cheaper than grid power. Moreover, solar is a one-time investment while grid tariffs will keep rising in future. An investment into solar energy today will help you against the future cost increase of grid energy.

The primary difference between solar power and grid power is the supply of electricity. Solar power is the power generated and supplied through a solar PV system. While grid power is generated through various sources (Renewable or Non-Renewable) and the supply of electricity is through a common distribution and transmission system to the user.

The cost of solar energy has dropped significantly over the last few years and subsidy is in most cases not required anymore for financial viability. However, in some cases, the Government of India, through the Ministry of New and Renewable Energy and its state-wise nodal agencies, provides a capital subsidy for the investments in solar systems.

Capital subsidy can be defined as a subsidy that can be availed on the capital expenditure of the project.

CAPEX and OPEX (RESCO) are two models of installing rooftop solar systems, CAPEX stands for Capital Expenditure. If you install solar PV under the CAPEX model, you are required to pay the total cost of the solar system upfront. This allows you to own the solar system and makes you eligible to avail the accelerated depreciation benefits.
OPEX stands for Operating Expenditure. If you install rooftop solar PV under this model, you essentially choose not to own the solar system. You rather buy the units of solar energy produced by the solar system on your premises. The solar system in this mode is installed and owned by the solar installer or a third party and you are required to sign a Power Purchase Agreement (PPA) for purchasing the electricity from the solar system at a specified rate for a certain number of years. These agreements are usually signed for 15~25 years.

There are a few criteria that everyone should use when choosing a solar installer. Confirm that they are certified, licensed and insured, have relevant experience, and can provide references. You may also get recommendations for installers from your network. Get quotations from multiple solar installers before deciding on the installation. Meet your solar installer in person and get a site audit done before you sign an agreement.

Solar power systems that include solar batteries, known as solar-plus-storage, are increasingly popular, but can be expensive. Luckily, batteries are not necessary for most solar homeowners. As long as you are connected to the grid, your system does not need a battery: excess power goes back to the grid, and you can draw from the grid if you need more electricity than your panels can generate. However, if you are in a location with frequent power outages a solar plus battery storage system can be an attractive solution and can replace your existing power backup solution.

A solar system has solar panels, a battery, a hybrid inverter (or possibly multiple inverters), plus a connection to the main electricity grid. The solar panels supply power during the day, and the home generally uses the solar power first, using any excess to charge the battery. At times of high power usage, or at night and on low-sunlight days, the home draws power from the battery, and as a last resort from the grid. Depending on your electricity tariff, using electricity from your battery can be cheaper per kilowatt-hour than using electricity from the grid.

TOD tariff is a tariff structure in which different rates are applicable for your use of electricity at different times of the day. It means that the cost of using 1 unit of electricity will be different in mornings, noon, evenings and nights. This means that using your appliances during certain times of the day will be cheaper than using them during other times. If you have a solar plus battery storage system you can draw storage solar energy during hours with higher tariffs to reduce your electricity charges. Check your electricity bill to see if TOD tariffs are applicable to you.

If you are in a state in which solar net feed-in, net metering or gross metering is applicable or if you intend to install a solar plus battery storage system, having an accurate estimate on your electricity consumption (load profile) helps in optimising your rooftop solar capacity and energy storage requirement. For more please see: (reference to blog)

Solsavi helps you to evaluate your optimum Solar panel and Battery size based on your load pattern, local solar policies, economic feasibility and metering mechanism. The tool will help you determine the capacity of your solar panel & battery storage and also calculate the possible savings from installation of the system. Solsavi also provides the potential carbon emission (Co2eq) reduction on installation of the suggested system. The tool can be utilised as an aid for decision makers who are interested to install rooftop solar and find the potential savings for a period of 25 years.

The application collects multiple inputs from the user to determine the location, metering mechanism, interconnection voltage (LT or HT), consumer category, consumption pattern and battery technology suggestion. Additionally, certain assumptions with respect to the technology, O&M & economical parameters are considered for the analysis. Through the provided inputs, the weather information and tariff details for the specific location are retrieved from a database. From the consumption pattern provided by the user a load curve is generated. Suggestion for technology is taken from the user. In case when the user selects ‘Optimise’ option on the run page, multiple inputs collected from the user and information retrieved from the database are processed through an optimiser to provide an optimum solar panel and battery size, based on minimising the payback period. Further the optimised solar panel and battery size are processed through a calculator which determines the potential investment and savings for a period of 25 years. In case when the user selects ‘Customise’ option on the run page, the user is prompted to enter the desired solar panel and the battery size. The collected information is further processed through the calculator to determine the potential investments and savings for a period of 25 years.

It is an online tool and can be used as a decision making tool for grid connected rooftop solar installation. Developers and solar rooftop installers are the ones who can use the tool. Initially the details for TN are fed in the database but gradually the details of all the states will be uploaded in the database.

Solsavi is a free tool and can be utilised by a user interested to install rooftop solar panels to reap benefits in form of potential savings and reduction in carbon emissions.

Refer Solsavi to people planning to adapt rooftop solar

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