There are many aspects one should keep in mind while setting up solar panels. Few important factors such as do you have sufficient open space on your roof or does your region get sufficient sunlight during the year? Although India is considered a sunshine country, few states get maximum benefits for getting a solar system such as Rajasthan and Gujarat.
One important question you should ask your installer if he is using the correct direction to set up the solar system. Basic theory behind the direction of solar panel is that better the angle of solar panels, better will be the output from your solar plant. For India thumb rule is to set up the panels in the direction of south. The reason for that is because India falls on northern hemisphere so most of the time sun will be available directly over south facing panels.
Another important factor is the tilt of solar panels. Tilt angle should be decided based on where you are setting up the system. It is based on the latitude of the place. Generally solar installers will use software like PVsyst to determine tilt angle for your location. But generally it is considered around 12 degrees for southern part of India and 30 degree for northern part of India.
Let us know what angle and direction your solar plant is installed.