Sizing, Payback Examples and Checklists
Rooftop solar for housing societies and RWAs: subsidy, approvals and a worked example
How apartment societies and RWAs in India can install rooftop solar for common areas, the PM Surya Ghar CFA of ₹18,000 per kW, approvals, metering options and cost sharing.
An apartment society or resident welfare association can install rooftop solar on the common terrace to supply common loads, such as lifts, water pumps, corridor and street lighting and EV charging, and claim PM Surya Ghar central financial assistance of ₹18,000 per kW (₹19,800 in special category states and UTs). The CFA is available up to 500 kW, counted at 3 kW per house, and that limit includes rooftop systems installed by individual residents. The usual route is a general body resolution, a structural check of the terrace, an application on the national portal in the society's name against its common-area electricity connection, a registered vendor using DCR modules, and DISCOM net metering. Because common-area bills are often large, a society system can pay back faster than a single home's. This guide explains the steps, the choices and the arithmetic.
What the subsidy covers
| Point | Position under the scheme pattern published by MNRE |
|---|---|
| Who applies | Group housing society (GHS) or RWA, as a registered body with its own electricity connection |
| What it is for | Common facilities, including EV charging |
| CFA rate | ₹18,000 per kW (₹19,800 in special category states/UTs) |
| Capacity limit for CFA | Up to 500 kW, at 3 kW per house, including individual residents' rooftop systems |
| Module condition | DCR modules, as for individual households |
So a 40-flat society could claim CFA on up to 40 × 3 = 120 kW, minus any capacity already subsidised for individual flats in the building.
Steps for a society
- Collect data: 12 months of common-area bills (all connections: lifts, pumps, lighting, clubhouse), the sanctioned load of each, and the terrace area free of water tanks, lift machine rooms and antennas.
- Structural check: ask a qualified structural engineer to confirm the terrace can carry the structure, ballast and wind loads, and that waterproofing is sound. This protects the society and residents.
- Committee proposal and general body resolution: follow your bye-laws and the state's cooperative societies or apartment ownership law for approving capital expenditure and use of common property. Record the capacity, budget, funding source and how savings will be used.
- Invite quotations from vendors registered for your DISCOM on the national portal. Use a written scope, as in the solar quotation and vendor checklist.
- Apply on the portal in the society's or RWA's name, against the common-area consumer number.
- Installation, net metering and inspection by the DISCOM, then submit the society's bank details for CFA.
- Operation and maintenance: assign responsibility for cleaning, monitoring generation and following up on faults during the vendor's maintenance period.
Metering options
How the system connects depends on your state's regulations:
- Net metering on the common-area connection: the simplest. Solar offsets the society's common bill.
- Several common connections: if pumps and lifts are on separate connections, the system may only offset the one it is wired to unless your state allows aggregation.
- Group or virtual net metering: some states allow credits from one system to be shared across several connections, including individual flats. Availability and rules vary; check your SERC's rooftop regulations.
See net metering vs gross metering.
Worked example (illustrative)
A 60-flat society uses about 4,000 units a month on common loads, at an illustrative ₹7.50 per unit for the units solar will replace.
- Size: 4,000 ÷ 120 ≈ 33 kW. The terrace has room for 35 kW. CFA limit: 60 × 3 = 180 kW, so not binding.
- Price: 33 × ₹50,000 = ₹16,50,000 including GST (illustrative; larger systems usually cost less per kW).
- CFA: 33 × ₹18,000 = ₹5,94,000.
- Net cost: ₹10,56,000, about ₹17,600 per flat if shared equally.
- Generation: 33 × 1,300 = 42,900 units a year.
- Saving: 42,900 × ₹7.50 = ₹3,21,750 a year, about ₹5,360 per flat.
- Simple payback ≈ 3.3 years.
Paying for it
| Funding route | How it works | Points to agree |
|---|---|---|
| Sinking or corpus fund | Use existing reserves | Rules on use of the fund under bye-laws |
| One-time contribution | Equal or area-based share per flat | Treatment of flats that refuse or are vacant |
| Loan to the society | Bank loan repaid from the savings | Bank requirements for registered bodies |
| Lower maintenance charges | Savings passed on to residents | Record in the accounts each year |
Put the agreed method in the general body resolution. Disputes in societies usually start with unclear cost sharing.
Individual flat owners
If an individual resident wants panels on the common terrace for their own flat's connection, they need the society's permission and an allocated area, and the DISCOM must be able to connect the system to that flat's meter. Many societies prefer a single common system because it is simpler to maintain and fair to all.
Mistakes to avoid
- Skipping the structural and waterproofing check.
- Not recording who maintains the system after the vendor's period.
- Installing on a connection with low daytime use in a state that pays little for surplus.
- Forgetting access for cleaning and fire safety: keep walkways and leave space around tanks and machine rooms.
Back to the pillar guide: how many kW of solar you need. Related: PM Surya Ghar subsidy explained, payback worked examples.
Frequently asked questions
Does every resident have to agree?
Approval follows your bye-laws and state law, usually a majority at a properly called general body meeting. Record dissent and how costs will be handled.
Can the society claim both the RWA CFA and individual CFA?
The 500 kW and 3 kW-per-house limit counts both together, so individual systems reduce the capacity the society can claim.
Who owns the system?
The society, as common property. Keep the invoice, warranties and portal records in its name.
When should we consult a professional?
For structural assessment, for contracts above a large amount, and for disputes among members, consult a structural engineer, a chartered accountant or an advocate.
Official sources
- PM Surya Ghar national portal — GHS/RWA application and vendor list
- Ministry of New and Renewable Energy — scheme guidelines for GHS/RWA
- Forum of Regulators — links to your SERC's rooftop regulations
