Tired of paying steep electricity bills? Rooftop solar power installations can be pocket-friendly as well as an environment-friendly option. The Centre’s PM Surya Ghar scheme – one of the many centrally sponsored schemes now being made more available with the change of regime – makes it convenient to go solar in Kolkata or Bengal.
There is a caveat, though. If you live in an apartment, it might not be feasible because you need roof area to install the panels.
A shared roof, if consented to by all apartment owners, can be used for solar power generation.
Is rooftop solar right for your home?
Experts say the decision to install a rooftop solar electricity system should not be based on the size of the house alone. Monthly electricity consumption, the availability of an unobstructed rooftop and adequate sunlight are the factors that determine whether a solar power system will be effective.
"The first thing we determine is the household's monthly electricity consumption,” said Anupam Boral, founder and CEO, Geetanjali Solar, a renewable energy company in Kolkata, specialising in the design, manufacturing and installation of customised solar-power systems.
Several companies, including Tata Power Solaroof, Vikram Solar and Jupiter Solar Power, are also offering rooftop solar solutions in Kolkata.
“Our primary objective is to determine how many units of electricity the house consumes each month. Whether it's 60, 80, 100 or 150 units, that's the key figure."
The consumption determines the size of the solar units needed for the generation of electricity – more the consumption, bigger the units needed.
As a rule of thumb, a monthly electricity bill of around Rs 2,000 generally translates into a requirement of a 2-kilowatt rooftop solar system. Seasonal fluctuations, particularly during Kolkata's humid summers when air-conditioners run for longer hours, are also taken into account.
A 2-kilowatt solar unit takes approximately 200 square feet of concrete space for installation.
Electricity bill determines the system size
"Most homeowners don’t know how many units they consume every month, but they know how much they pay for their electricity. From that, we estimate the monthly consumption and calculate the required solar capacity," Boral said.
According to industry estimates, a household paying around Rs 2,000 a month for electricity would typically require a 2-kilowatt rooftop solar system.
Experts also factor in seasonal changes, particularly Kolkata's humid summers, when air-conditioners push up electricity consumption.
"If the summer bill is Rs 4,000 and the winter bill is Rs 2,000, we take an average and may recommend a 3-kilowatt system instead. These are practical estimates because household electricity consumption keeps changing over time," Boral said.
Roof space, sunlight and installation costs
Available rooftop space is another key consideration. A standard 2-kilowatt solar system usually requires about 200 square feet of reinforced concrete roof. The installation cost, excluding GST, is approximately Rs 1.5 lakh.
It is a one-time investment.
Tin roofs can often accommodate panels more efficiently because the structures allow closer placement. But roof size alone is not enough.
"Solar panels require direct sunlight. Even if a single panel in a series is partially shaded, it affects the performance of the entire series. That's why we always inspect neighbouring buildings and trees which might cast a shadow on the panels before recommending an installation," Boral explained.
Net metering and the PM Surya Ghar scheme
Homeowners opting for rooftop solar under the PM Surya Ghar scheme can apply for loans through the Jan Samarth portal using their electricity consumer number.
To receive the subsidy provided by the Union Ministry of New and Renewable Energy, consumers must install a net meter.
A net meter is a bi-directional device that measures the electricity you pull from the local power grid (import) and the surplus solar energy you send back (export). The utility calculates your monthly bill by subtracting the exported energy from the imported energy, ensuring you only pay for your "net" consumption.
A net meter starts from Rs 3,000 and can be purchased from your electric service provider or the open market. Permissions for a net meter are given by West Bengal State Electricity Distribution Company Limited (WBSEDCL) or Calcutta Electric Supply Corporation (CESC) in Bengal.
This system allows excess electricity generated by the rooftop panels to be supplied back to the grid, reducing overall electricity costs.
A homeowner's experience
Kalighat resident Moushumi Pal invested in rooftop solar three years ago and says it has significantly reduced household electricity expenses.
Her two-storey home runs on a hybrid system that combines solar energy with conventional grid power when solar generation falls.
"In summer, our electric bill is zero. During monsoon and winter, when the sunlight isn't as strong, we switch to hybrid mode. But still the bills vary from Rs 500 to Rs 600," she said.
To opt for a hybrid mode, you need a net meter installation and to apply through your local utility provider for the process.
Institutions are also making the switch
Some educational institutions in the city have embraced rooftop solar as part of their sustainability initiatives.
The Tara Devi Harakh Chand Kankaria Jain College in north Kolkata’s Cossipore has been using the system for the last five years.
"The panels were installed during the pandemic in 2021. We built the infrastructure and involved the students in learning about solar energy and how sustainable it is," said Mausumi Singh Sengupta, principal of the college.
"We went for an energy audit at the college in 2023. We found out that we can save 25 per cent of the solar power harvested through the panels," she added.
Subsidies and the road ahead
According to Santi Pada Gon Chaudhuri, former secretary at the power department in the Bengal government, the dip in installation costs would make rooftop solar more affordable in the coming days.
"The PM Surya Ghar programme aims to install rooftop solar systems in 1 crore households. The Government of India provides subsidies up to Rs 78,000, while the West Bengal government has announced an additional subsidy of Rs 5,000 for Scheduled Caste and Scheduled Tribe beneficiaries," he said.
An option without upfront investment
For consumers who do not want to bear the initial installation cost, a new business model is gradually gaining popularity.
Under the OPEX model, a third-party developer installs and owns the rooftop solar system, while the homeowner purchases electricity generated by the panels at rates lower than conventional grid tariffs.
"This is known as the OPEX model and is beneficial for both the developer and consumer," Gon Chaudhuri said.
To get an OPEX model in solar energy, you sign a long-term Power Purchase Agreement (PPA) with a third-party developer or Renewable Energy Service Company (RESCO). The developer handles 100 per cent of the upfront capital, installation, and ongoing maintenance, while you simply pay a fixed, discounted rate for the electricity generated.
Here’s a step-by-step on how to apply for solar energy for your home:
- Visit the National Portal for Rooftop Solar to register. You will need your mobile number, email, CESC or WBSEDCL electricity consumer number and details from your latest power bill.
- Once submitted, your application is sent to your local utility provider (CESC or WBSEDCL). Engineers will then review your roof's feasibility and contractual load (the maximum power you are allowed to draw). Approval typically takes seven to 15 days.
- After receiving the feasibility approval, select a Union Ministry of New and Renewable Energy-empanelled vendor (names mentioned above in the article) to install your system. A typical 2kW on-grid system costs roughly Rs 1.65 to Rs 1.95 lakh before subsidy, which is enough to power typical household appliances, including one AC.
- The chosen vendor will handle the physical installation. Ensure the solar panels and inverter used are from the Approved List of Models and Manufacturers (ALMM) to qualify for government subsidies.
- After installation, you must apply for a bi-directional net meter. This meter tracks the solar energy you export to the grid versus what you consume. CESC or WBSEDCL officials will inspect the setup and install the net meter.
- Once the net meter is installed and the system is successfully inspected, the electricity provider (CESC or WBSEDCL) will generate an online commissioning certificate.
- Submit your bank account details and a cancelled cheque through the PM Surya Ghar Muft Bijli Yojana Portal. The central government subsidy will be credited directly to your bank account within 30 days.