Start with the common-meter bill
Collect 12 months of common-area bills. Note the monthly units, the sanctioned load and the tariff category. Common loads such as lifts, pumps, the STP and lighting run through the day, which matches solar generation.
Estimate the plant size
Use two limits and take the smaller one:
- Load limit: monthly daytime units divided by about 125 units per kW per month (4 to 4.5 units per kW per day).
- Roof limit: usable shadow-free area divided by roughly 80 to 100 sq ft per kW.
Illustration: a society using 6,000 common-area units a month could, on load alone, use about 48 kW. If the shadow-free roof fits only 30 kW, the roof is the limit.
What the subsidy gives
Under PM Surya Ghar, RWAs receive ₹18,000 per kW for common facilities up to 500 kW, calculated at 3 kW per house and inclusive of individual rooftop plants in the society. For a 30 kW plant this works out to ₹5.4 lakh. Confirm the current terms before budgeting.
Metering routes
- Net metering on the common-area connection.
- Group net metering across multiple connections of the same consumer.
- Virtual net metering to share one plant across several consumers.
See virtual and group net metering for the details.
Prepare for the AGM
Committees decide faster with a one-page summary: plant size, yearly generation, monthly saving on the common meter, saving per flat, subsidy, total cost, annual maintenance and payback. Present two or three options, and note the assumptions.
Roof rights and safety
Confirm who controls the roof, where the plant sits relative to water tanks and lift rooms, how modules and cables reach the roof, waterproofing, lightning protection and fire access. Society projects stall most often on roof rights and access.
Operating the plant
Assign someone to monitor daily generation and to arrange cleaning. A maintenance contract with a clear scope and a yearly cost removes the guesswork. See our AMC service.
Frequently asked questions
Who owns the solar plant in an apartment society?
Usually the society, funded from its corpus or a special levy, with the subsidy applied to the cost. Ownership and payment terms should be written into the contract.
How are savings shared among residents?
Savings on the common meter reduce the maintenance charge for everyone. Residents with their own rooftop plants are separate and count towards the 500 kW subsidy limit.
Keep reading
Need a solar proposal for your managing committee?
We prepare the plant size, yearly generation, per-flat saving and the ₹18,000/kW subsidy numbers in a format your committee can take to the AGM. Tap Free Survey to start, or call us.
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