Implementation of Solar rooftop project:

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Solar rooftop project installation: Is your roof suitable for installation of solar PV?

The first step in the project development process is to assess whether it is even worthwhile to proceed. Undertaking that assessment, which is also known as conducting a prefeasibility study, can evaluate a number of factors depending on the individual needs of the rooftop owner. One of the steps involved in prefeasibility study is checking the suitability of the roof for installation of solar PV.

A rooftop solar PV installation comprises of Solar PV panels assembled in arrays, module mounting structures (MMS) to support the panels and secure them to the roof, wiring, inverters, and other components (BoS) depending on the type of installation. The roof site must be able to accommodate all of these components.

For evaluating this, there is a need of examining the following aspects:


The roof must be accessible to carry out installation and maintenance. It must be possible to lift the solar system components onto the roof and for personnel to physically access the roof to install and maintain the system.

Roof configuration.

The orientation of the rooftop towards the sun is important. South exposure is the ideal orientation for the panel. If the roof is naturally sloping and facing towards south, then it is very ideal for installing rooftop solar panels. This is because India is situated in the northern hemisphere and south facing rooftops receive the maximum amount of sunlight as the earth rotates on its own axis at an inclination. However, if the roof is flat, then the solar panels will need to be installed at an angle facing south to receive the maximum possible sunlight. A roof plan can help quantify the roof area available for the PV power plant. The plan should indicate the location (including longitude and latitude), height, and slope of the roof itself, as well as any additional structures present on the roof. Also, identify any possible conflicts in usage of the roof, such as a communication antenna, and contact relevant bodies to ascertain if any special permission is required to use and/or alter usage of the roof space.

Roof materials and structure.

In the case of old roofs, first determine the remaining life span of the roof. If a roof is nearing the end of its life span, it makes more sense to repair or replace the roof first. Making changes to the roof after solar panels have been installed is more expensive, as they will have to be removed first. Also, it is better to integrate a system into a new roof from the stage of designing.

Also, determine if the roof can be drilled to secure the mounting frames. Many times, flat roofs will lose its waterproofing properties if drilled—in this case, the ballasted mounting system (with concrete weights) is suggested.

The engineer should also determine the weight bearing capacity of the roof to bear the additional weight of a PV system. As a general rule of thumb, a crystalline PV system will place about 15–20 kilograms per square meter (kg/m2) of dead load on the roof, but this varies depending on the panels and mounting system used, the spacing between panels, and the wind load.

In general, a flat, concrete terrace roof will normally have the strength to bear the additional weight of the solar panels and supporting structures. But in the case of inclined roofs made of metal sheet, tiles, or similar materials, it would be necessary to check whether the trusses can support additional weight.

If the roof is unable to support the load of a crystalline PV system, then lighter thin-film modules could be an option.

Also, check for the warranty violation of the installed roof structure due to installation of panel over it.


The area for the installation of Solar panel must be shadow free. During the site feasibility, check for the shading elements such as nearby buildings/structures, trees, water tanks, etc. which can shade a roof during certain periods of the day and will lower the power output of the solar PV system. The roof must be observed at various times during a day to get the idea of typical sun hours as the shading changes throughout a year.


Check that the solar PV modules would not negatively affect the aesthetics of the building. As solar modules will be more visible on a sloped roof than on a flat roof from street level.

Roof leasing

Before leasing the roof space to a solar developer (owner of the rooftop PV system), consult a legal advisor to confirm whether that type of arrangement is permissible in your area or not.

Electrical load

To calculate the capacity to be installed, also check for the sanctioned load or and load profile of the building. Electricity bills of the buildings can be referred for this. Either plan a system of smaller size than the actual consumption of the building or plan to use the excess energy—either store the energy in batteries, send it to another building within the facility, or feed it into the grid.

During the designing phase of a new building, above mentioned aspects can easily be incorporated.

However, the investigation will take more effort for solar installations on an existing roof.