Such rooftop system has battery as storage facility. The solar electricity is stored in the battery and can be utilized during night also when the sun is not available

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

Such rooftop systems can be installed at the roofs of residential and commercial complex, housing societies, community centers, government organizations, private institutions etc.

The average cost of grid connected rooftop solar systems is about Rs. 80 per watt but cost decreases significantly as the system size increases.

There is a provision of Central Financial Assistance of 30% of the total cost or Rs. 18 per watt under the Grid Connected Rooftop and Small Solar Plants Programme of the Ministry. But this subsidy is available only to residential and charitable consumers.

There are provisions of concessional import duty/excise duty exemption, accelerated depreciation for setting up of grid connected rooftop power plants

Department of Financial services has instructed to all Public Sector Banks to encourage home loan/ home improvement loan seekers to install rooftop solar PV plants and include cost of system in their home loan proposals. So far, nine PSBs namely Bank of India, Syndicate Bank, State Bank of India, Dena Bank , Central Bank of India, Punjab National Bank, Allahabad Bank, Indian Bank and Indian Overseas Bank have given instructions to extend loan for Grid Interactive Rooftop Solar PV Plants as home loan/ home improvement loan.

The rooftop solar systems from 1 kWp upto 1000 kWp can be set up on the roofs

About 10sq.m area is required to set up 1 kWp grid connected rooftop solar system

Electricity generation at the consumption centre and hence Savings in transmission and distribution losses • Low gestation time • No requirement of additional land • Improvement of tail-end grid voltages and reduction in system congestion with higher self-consumption of solar electricity • Local employment generation

According to a study conducted by TERI, a potential of 124 GWp SPV Rooftop plants has been estimated in the country. This can be achieved through active supports from the States.

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.

In case the grid fails, the solar power has to be fully utilized or stopped immediately feeding to the grid so as to safe-guard any grid person/technician from getting shock (electrocuted) while working on the grid for maintenance etc. This feature is termed as ‘Islanding Protection’.

(i) States should have conducive solar policy to allow the grid connectivity. (ii) State Regulators have issued tariff order for appropriate tariff, net-metering/feed-in tariff and the grid connectivity, and (iii)The Distribution Companies agree to allow grid connectivity and purchase the electricity on feed-in-tariff or through net metering arrangement.

The Projects under these guidelines fall within two broad categories i.e.(a) the projects connected to HT voltage at distribution network (i.e. below 33 kV) (b) the projects connected to LT voltage i.e. 400/415/440 volts (3-phase) as the case may be or 230 volts (1-phase).

There can be many possible business models, some of which can be considered are as follows: (a) Solar installations owned by consumer
i) Solar Rooftop facility owned, operated and maintained by the consumer(s).
ii) Solar Rooftop facility owned by consumer but operated and maintained by the 3rd party.
(b) Solar installations owned, operated and maintained by 3rd Party If the 3rd party implements the solar facility and provides services to the consumers, combinations could be: i) Arrangement as a captive generating plant for the roof owners The 3rd party implements the facility at the roof or within the premise of the consumers; the consumer may or may not invest as equity in the facility as mutually agreed between them. The power is then sold to the roof owner.
ii) Solar Lease Model, Sale to Grid The 3rd party implementing the solar facility shall enter into a lease agreement with the consumer for medium to long term basis on rent. The facility is entirely owned by the 3rd party and consumer is not required to make any investment in facility. The power generated is fed into the grid and the roof top owner gets a rent.

1 kwp system will generate 4 units of electricity per day on average