Rooftop Solar Power Generation


Solar energy in India is most beneficial for industries, particularly rooftop solar plant. Of the revised target of 100 GW, 40 GW has been reserved for rooftop solar energy and the balance for utility scale ground mounted plants. The new trend of solar energy in India analyses that industries should adopt rooftop solar in current fiscal itself, solar energy in India is increasingly becoming competitive with grid. Rooftop solar power are still competitive and give a better control over consumption. Accelerated depreciation benefits for industries will be reduced to 40% from next fiscal reducing the overall tax benefits. Apart from these, network losses are negligible, consumer is able to offset his surplus solar units on electricity bill.


Ways to have solar energy generation & utilisation are very simple and depends on State Electricity Boards. Owner can invest in solar plant on roof/land within his premises and use fir own power consumption and in case of excess power generation, he can sales back to Grid, this option is suitable for industrial clients. Owner can also invest solar plant outside premises and use for own consumption. Or third party (contractor) can invest on solar plant on roof/land and sales power to client as per unit basis. Another way is third party (Investor) can invest on solar plant on roof/land and sales power to client as per unit basis through PPA (Power Purchase Agreement).


There are contractual agreement for industrial projects depending upon utilisation and generation of Energy. Owner can utilise only the ‘Energy’ generated from roof top solar PV or he can utilise both ‘Energy from rooftop’ as well as renewable source of energy for meeting PPA of renewable credits. Owner can avail renewable power max. 50% of sanctioned load/demand of Owner as per Gujarat Solar Power Policy. In case of surplus power with owner, shall be purchased by Discoms at Average Pooled Power Purchase cost rate of the year in which solar power generation is commissioned at the end of the billing cycle.

Mostly there are three types of PV cells have been used for solar power generation i) polycrystalline silicon, ii) Monocrystalline silicon, iii) Thin film silicon. Thin film silicon cells are not recommended to use on roof top. Due to availability and low cost, Polycrystalline Silicon based PV cells are widely used.

Installing 100 kW roof top solar power plant it would cost you around Rs.45 Lac, cost may change according to size of generation capacity and subsidy obtained from state and central government. Nearly 20 kg/ Sq. Meter dead load can be considered for roof design. If standing seam roofing sheet is installed then panels can be installed without picturing. However for screw down sheet, panel shall be installed by puncturing with waterproofing guarantee from solar panel vendors. Generally 1 kW of solar panel will take around 10 Sq. Meter roof area if roof is south facing and 17 Sq. Meter per KW for north facing inclusive of space required for maintain ace and manoeuvring. Solar panel requires maintenance like dust removal, twice in a week.

Solar panel works at maximum efficiency of 80 % between 11 AM to 3 PM in summer and winter. Average payback of solar plant depends on Government Policies and Location of plant, but general it can be estimated to be 4-6 years, any case not more than this.

For initial capital investment and decision making to have solar roof top system certain points should be clear from client’s side. Usable roof top area excluding shading, roof monitor, sky lights and raceways and facing of roof top are major factors for design consideration. Capital Investment items includes PV modules, Inverter, Cabling and other Electrical equipment and structure support as well as fabrication. Return investment calculation are based on cost of energy generated from solar system, maintenance cost, rate of interest if money deposited in banks as well as time period of Investment.

However all the calculation may vary according to cost of capital items, efficiency of solar panel, State Electricity Board policy for purchase and selling of energy units. Before coming to any decision it is very essential to consider the economy and ecology aspects, but one thing is certain that solar energy is our future!