A solar rooftop system is a type of solar panel system that is installed on the roof of a building. It converts sunlight into electricity that can be used to power the building or sent back to the grid. It typically consists of solar panels, an inverter, and a monitoring system. These systems can be used to reduce a building’s reliance on the grid, lower energy costs, and reduce carbon emissions. 

There are a few different types of solar rooftop systems, including:

• On-grid systems: These systems are connected to the utility grid, allowing excess energy generated by the panels to be sent back to the grid and credited to the homeowner.
• Off-grid systems: These systems are not connected to the utility grid and rely on battery storage to store excess energy for use during times when the sun is not shining.

 An on-grid solar rooftop system is a type of solar panel system that is connected to the utility grid. This allows excess energy generated by the panels to be sent back to the grid and credited to the homeowner. The system is connected to the utility grid through a bi-directional meter, which allows the homeowner to receive credits for the excess energy they produce and also draw power from the grid when their solar panels are not producing enough energy to meet their needs.

This type of system is ideal for homes or buildings that are connected to the grid and want to reduce their dependence on fossil fuels and lower their energy costs. It also allows for net metering, which is a mechanism for homeowners to get credits for the energy they feed back into the grid.

The on-grid solar rooftop system is also useful for homes or buildings that are not occupied all the time, or for homes or buildings where energy consumption is not constant throughout the day, as the excess energy generated can be sent back to the grid for others to use.

An off-grid solar rooftop system is a type of solar panel system that is not connected to the utility grid. Instead, it relies on battery storage to store excess energy generated by the solar panels for use during times when the sun is not shining. This type of system is ideal for homes or buildings that are located in remote areas where access to the utility grid is not available or is too expensive to install.

An off-grid solar rooftop system typically includes solar panels, an inverter, a battery bank, and a monitoring system. The solar panels convert sunlight into electricity, which is then sent to the inverter to convert it into usable AC power. The excess energy is then stored in the battery bank for use during times when the sun is not shining or for use as backup power during grid outages.

The main advantage of an off-grid solar rooftop system is that it allows for energy independence and can provide power in remote or off-grid locations. However, it also requires careful management of the battery bank to ensure that the batteries are not overcharged or over-discharged, which can lead to a decrease in their lifespan. Additionally, off-grid systems may require more maintenance and can be more expensive to install than on-grid systems because it requires a battery bank and the maintenance cost of battery is high.

 In India, the government provides various subsidies and incentives for the installation of solar rooftop systems. The subsidy and incentives schemes are implemented by the Ministry of New and Renewable Energy (MNRE) and the state governments. The main subsidy scheme for residential and commercial rooftop systems is the Capital Subsidy Scheme, which provides a subsidy of 30% of the benchmark cost for systems up to 3 kW and 20% for systems above 3 kW and up to 10 kW.

In addition to the capital subsidy, there are also other incentives available such as:

• Generation-based Incentive (GBI): This provides a financial incentive for every unit of electricity generated by the solar rooftop system and fed back into the grid.
• Net metering: it allows the consumer to get credit for the excess energy sent to the grid.