The solar rooftop solutions are the most sought-after applications of solar energy. As the name indicates these solutions are installed in the rooftop of any building (both domestic and commercial). There two type of roof top solutions – Off-grid and On-grid / grid-tie. Here the word ‘grid’ refers to the electric power line of the utility company (in case of Assam it is APDCL).

The capacity of any solar power plant is measured by the capacity of the solar photovoltaic modules used in that plant. There are two types of solar PV modules – mono crystalline and poly crystalline. The productivity of mono crystalline/ mono perc modules is higher than the poly crystalline modules.

An on-grid solution is also known as a grid connected solar power plant. This on-grid system is the one which is connected to the power line / energy grid of the utility company. The on-grid or a grid connected solar systems can generate power when the utility power grid is available. The system must be connected to the grid to function. These systems can export any excess power generated by solar back to the utility grid and facilitate credit from the utility company to the user.

A grid connected solar solutions is the most popular and economically viable option available to buyers. This system of capable of generating and supplying electricity to the user directly by converting it from DC to AC by the help of the Grid-tie inverter. As this system does not have battery it can’t store the energy within itself and rather uses the utility grid for storage purpose. To facilitate energy injection/ export to the grid the energy meter of the buyer needs to be replaced by one bi-directional energy meter.

The Assam Solar Energy Policy 2017 has made clear provision for individual buyers to export the surplus energy generated to the grid of APDCL. However, to avail this facility one must take prior approval (NOC) from APDCL.
The grid-connected solar system is very useful for industrial and commercial users. The reason is that unlike residence the industry/ commercial establishment consumes most of their energy during the day time and hence by installing such a system they can reduce their purchase from the utility grid during the day time to the extent of their own captive solar production. Moreover, they can enjoy credit from DISCOM (utility company) by injecting the surplus energy on Sundays and holidays.

The situation is little different for residence as majority of the energy consumption in residence occurs during the evening time (say 5 to 11 pm). The residential users can get benefits by using solar energy during day time as per their load and the surplus can be exported to the grid and enjoy credit from the DISCOM. It is considered to be more beneficial to set up a solar plant by an individual as per the requirement for consumption rather than setting up a bigger plant with an objective to export/ sell energy to the grid and earn out of it. Therefore, it is very critical and essential for the buyers to do proper assessment of their requirement before deciding to buy / install a solar plant. The more the optimization in size/ capacity, the more will be the benefits to the buyers.

Another advantage of a grid-connected system is that one can keep increasing its capacity by just adding solar modules and inverters (string inverters) with the existing one. Whereas, in case off-grid the capacity of the inverter cannot be increased like this.