Step 1 - there is no public electricity grid present in an off-grid system. Household appliances use the solar power and excess power (remaining power after using in the house) will be sent to the battery bank. Once the battery bank is full it will stop receiving power from the solar system. When the solar panel stops working such as night time or cloudy days, household appliances will start using the power from the battery bank.

Step 2 : due to weather condition majorly in cloudy weather, many times of the year when batteries are low on charge, we need a backup power source called backup generator or gen-set. The size of the backup generator of gen-set must be according to the consumption of the supply in the house.

What is a Solar Rooftop Power Plant?
In a Solar Rooftop Power Plant, solar panels are installed on the roofs of any residential, commercial industrial or institutional buildings.

How much area is required to install a Solar Rooftop Power Plant?
Typically, 1 kW Solar Plant requires shadow free rooftop area of minimum 10 sq. Mt. Therefore to install a plant of size 30 kW you need at least 300 sq.mt.

How much does a Solar Rooftop Power Plant Cost?
The cost of a rooftop solar PV system depends on the function it serves (to feed power into the grid,to support the load during a power failure, etc.) And incentives subsidies available. Cost also depends upon the type of system viz Grid Connected or off-Grid Power Plant as well as the size of the system. 1 kw Grid Connected system will cost around Rs. 90,000/- to Rs. 100,000/- As the size of system increases, cost tend to come down. The above prices are for components from Tier 1 manufacturers with 5-year manufacturer’s warranty. In addition the PV modules have output warranty of 90% of rated capacity for the first 10 years and 80% of rated capacity for the next 15 years. Cost of battery backup has not been considered as that can alter the economics significantly depending on the extent of backup (autonomy) required. Not only do batteries add to the initial cost but also recurring maintenance, and replacement expenditure as well as the energy loss on charging and drawing from the battery also adds to the cost of power. A battery backup could add significant costs to the above system.