• Rooftop solar on new residential buildings can help install up to 3 GW of new rooftop capacity in the next five to seven years, according to a new report called "Solar Rooftop: Replacing Diesel Generators in Residential Societies"
  • Replacing diesel generator sets with rooftop solar panels can bring down the cost of power generation by 50%
  • A change in the mindset is needed to make the necessary shift from diesel generation sets to rooftop solar as full power back up is not the basic need anymore in urban India
  • The report recommends banning diesel gensets in new multi-storied residential buildings and making rooftop solar mandatory for all new residential societies
  • To promote its idea, CSE has also come out with a website based rooftop solar calculator to help residential consumers install rooftop solar plant

If residential societies replace diesel generators (DG set) for power back-up with rooftop solar power systems, they will save 50% less on the cost of power generation. At the same time, India has the scope of installing 3 GW of solar rooftop capacity on new residential societies over the next five to seven years. A report and policy brief titled ‘Solar Rooftop: Replacing Diesel Generators in Residential Societies’ makes this recommendation. It has been published by the Centre for Science and Environment (CSE), a public interest research and advocacy organization in India.

As per this study, capital cost along with power generation cost from a DG set comes to a total of 27 INR to 33 INR ($0.40 to $0.48). Compared to this, the tariff for rooftop solar comes down to less than 10 INR ($0.15).

For the purpose of this report, CSE assessed the feasibility of installing rooftop solar panels in residential societies across Delhi, Haryana, Uttar Pradesh and Rajasthan. Deputy Director General of CSE, Chandra Bhushan said, “In all the residential societies that CSE studied and analysed, the cost of power from solar rooftop with battery back-up was found to be about half the cost of power generated by DG sets. This alone should make residential societies move away from the extremely polluting diesel generator and adopt solar rooftop to meet their power back-up needs.”

With the electricity situation improving over the years, full power back up is no more a ‘basic need’ as it was for upscale societies when the outages went on for several hours at a stretch. At such a time, installing a solar rooftop with battery storage makes more economic sense. Bhushan added, “Moving away from the DG set to solar rooftop requires a change in mindset. If power outage is less than a hour a day then the very definition of “full back-up” needs to be changed. For tens of minutes of outage, even for the
high end societies “partial load back-up” should be sufficient.” Partial load here refers to the basic load for individual flats covering lighting, fans and some communication and entertainment appliances.

The Indian government has been pushing on all fronts to encourage the use of rooftop PV. However, so far it has only been successful in getting its own departments and ministries to head towards solar rooftops (see India Launches 1 GW Rooftop PV Tender). Now commercial and institutional entities too are warming up to the idea to save on huge utility bills. But adoption of the same by common people is yet to take off owing to the capital cost involved, lack of awareness, among other issues. The government is also offering subsidies on capital cost, yet things seem to be moving slowly.

CSE argues up to 3 GW of solar rooftop capacity can come up on new residential homes in the next few years. This, it says, can be a key to achieving the country’s target of installing 40 GW of rooftop PV capacity by 2022, according to CSE researchers.

CSE has put forth a number of recommendations to push residential solar:

  • Make installation of solar rooftops mandatory for all upcoming residential societies.
  • Ban DG sets in new multi-storied residential buildings except for common area loads in polluted areas.
  • Support discoms to encourage them to push solar rooftop.
  • Provide subsidy for hybrid solar rooftop systems.
  • Increase awareness among residential welfare associations (RWAs) – provide single window information and initiate campaigns.
  • Initiate monitoring by regulatory authorities.

The policy brief is available for download here.


CES calculator for residential solar rooftop design in India

To promote its idea, CSE has also come out with a website based rooftop solar calculator to help residential consumers install rooftop solar plant. It covers the entire country. The users will need to enter pin code of the area to get feasibility analysis for a grid-connected, off-grid and hybrid systems based on the presence of grid power and battery. They will get a comparative analysis between the three kinds of systems and make their choice. It is similar to the Project Sunroof of Google that is only available in the US as of now.

The link for the rooftop calculator can be found here.

CSE has invited user feedback and suggestions on the calculator to upgrade it. Later on, it also plans to include solar plant installers in the area, including industrial and commercial sectors.