KOLKATA: Give us your rooftop and we will give you cheap solar power – this is the model being used by many solar power companies to rake up their rooftop solar installation capacities.Industrial establishments, commercial buildings, malls and large gated communities are the target for these operators who would set up solar rooftops for free and sell you power at rates that are cheaper than the local utilities.“Around 240 sq mt of rooftop space is good enough for setting up a rooftop solar power plant that can viably sell power to the building and earn some decent profits,” said Sunil Jain, chief executive of Hero Future Energies.“In fact, some five-six companies including Hero Future Energy have already entered the fray and are on the lookout for large rooftop space in industrial complexes, commercial buildings, malls and gated communities,” he said.According to officials, about 8sq mt of rooftop is required to set up panels to generate 1 kilo watt and a minimum capacity of 30 kW makes an installation viable. The power generated can help building owners cut down on power costs and gainfully use the roof which would otherwise remain unused.However, there are no model lease agreements and there is no way of making these agreements between the solar company and the roof owner a binding agreement. This has been one of the factors holding back the success of the large scale rooftop solar installations.“Nevertheless, with the cost of solar photo voltaic cells on the de-cline at a rapid rate, the cost of power generated from solar installations has been on the decline,” an official said.Cost of generating power differs in different places due to difference in the intensity of sun’s rays. For example, the sun is the strongest in Rajasthan and the intensity reduces as it moves towards east.“In Delhi, solar power can be made available between Rs 6.25 and Rs 7 per unit from rooftop installations. This is cheaper for the companies that consume large volumes of power,” said Jain.Additionally, it offers a shield against frequent power cuts and hedge against rising power costs as rooftop owners enter into long terms, mostly 25-year, agreements for buying the power at a fixed cost.In contrast, power tariffs of utilities are expected to rise at regular intervals. The model, popularly referred to as the OPEX – operational expense model – however, has its limitations when it comes to gated communities.“There is a feeling that the rooftop belongs to the families staying on the top floor, hence they feel that they are entitled to the power being generated from rooftop. But legally, the roof belongs to all flat owners and the power generated should be used for common purposes,” a senior executive from a solar power company said.“A standard format for legal documents and agreements for rooftop solar plants will go a long way is increasing rooftop installations even on residential apartments,” he said.