Solar for Apartments in Tamil Nadu: Sizing, Subsidy, Savings & Approvals

For an apartment community, going solar is not simply the same decision as installing solar on an individual house at a larger scale. The electricity being reduced is usually the society's common-area consumption, the rooftop is shared, multiple stakeholders are involved, and subsidy, metering and approvals depend on the common service connection.

A well-planned apartment solar project can reduce electricity purchased for lifts, water pumps, common lighting, security systems, sewage-treatment equipment, clubhouses, EV charging and other shared facilities. But the right system size should come from actual common-area electricity usage and rooftop feasibility — not simply from the number of flats or the maximum number of panels that can fit.

This guide explains how rooftop solar for apartments, housing societies and RWAs works in Tamil Nadu, including system sizing, common-area savings, PM Surya Ghar subsidy eligibility, roof feasibility, metering, approvals and the questions an association should resolve before selecting a solar proposal.

Most apartment communities have electricity loads that are separate from the electricity used inside individual flats. These common facilities may be supplied through one or more common service connections and paid for through association maintenance charges or other shared expenses.

A rooftop solar plant connected appropriately to the common service can generate electricity during the day and reduce the amount of electricity the association purchases from the grid.

The actual value of solar depends on when these loads operate. A society with meaningful daytime common-area consumption can use a larger portion of its solar generation directly, which can improve project economics.

There is no standard answer such as “3 kW per flat” for designing the actual common-area solar plant. The system should first be sized using the association's electricity consumption and site conditions.

A practical assessment begins with recent common-area electricity bills, service-connection details and the major shared loads operating throughout the property.

The goal is not to install the largest possible system. It is to identify a capacity that makes technical and financial sense for the association's actual electricity profile.

Apartment rooftops often appear large from the ground, but the total terrace area is rarely the same as the usable solar area.

Water tanks, lift rooms, staircases, ventilation structures, parapet walls, plumbing, telecom equipment, shaded areas, access pathways and maintenance requirements can all reduce the area available for panels.

A proper rooftop assessment should also consider the condition of the structure, mounting method, safe equipment access, cable routing, inverter placement, earthing and the ability to maintain both the solar plant and existing building services after installation.

Satellite images can help with a preliminary assessment, but the final layout should be based on an actual site survey. Small obstructions, changing shade, usable mounting zones and access constraints are often difficult to judge accurately from an aerial image alone.

For a housing society, the final proposal should therefore include a realistic panel layout rather than only quoting a system capacity.

Under the current PM Surya Ghar: Muft Bijli Yojana guidelines, eligible Group Housing Societies, Resident Welfare Associations, Apartment Owner Associations and similar resident entities can receive Central Financial Assistance for rooftop solar serving common facilities.

For Tamil Nadu, which falls under the general-state category, the current Central Financial Assistance for eligible GHS/RWA common-facility rooftop solar is ₹18,000 per kWp.

The scheme permits supported capacity for common facilities, including EV charging, up to 500 kWp, subject to a limit of 3 kWp per house. The overall supported-capacity ceiling also includes individual rooftop solar plants installed by residents within that GHS/RWA.

Important: the GHS/RWA connection receiving this common-facility subsidy must be dedicated to common facilities. It is not intended to become a single subsidized electricity source that directly supplies the individual residential consumption of every flat.

The eligible subsidized capacity is not automatically the entire solar plant size. It is constrained by the number of households, the installed system capacity, the overall 500 kWp ceiling and any individual rooftop systems that count toward the scheme limit.

At the current ₹18,000-per-kWp CFA rate, the scheme's own examples translate to ₹10.8 lakh of CFA on 60 kWp in the first example and ₹18 lakh on 100 kWp in the second example.

These examples explain the subsidy calculation; they should not be used to decide how large the apartment's solar plant should be. The actual project should still be sized using electricity consumption, roof feasibility and technical requirements.

MNRE has clarified that in certain residential projects where common facilities are still being managed by a developer or promoter because an RWA, GHS or Apartment Owner Association has not yet been constituted, CFA may be available subject to the prescribed undertakings.

Among other requirements, the rooftop solar asset must ultimately be handed over to the resident body when it is created, and the benefit of the subsidy must be passed on to residents through the common-facility charges or tariffs as applicable.

Because subsidy procedures can change, associations and developers should verify the latest National Portal and TNPDCL requirements before committing to a financial assumption.

One of the most important checks in an apartment solar project is the tariff category and structure of the common electricity service connection.

In Tamil Nadu, domestic consumers and non-domestic consumer categories do not necessarily use the same solar settlement mechanism. Eligible domestic consumers can use net metering under the applicable TNERC framework, while other consumer categories generally operate under net billing or net feed-in provisions.

An apartment association should therefore not assume that the metering arrangement used for an individual residential home will automatically apply to its common service.

The service number, tariff classification, sanctioned load, proposed solar capacity and applicable TNPDCL rules should be reviewed before the savings model is finalized.

This distinction matters because the value of solar electricity consumed directly inside the apartment complex may differ from the value received for surplus electricity exported to the grid.

The most useful starting point is the association's existing common-area electricity bill.

Solar savings depend on the amount of solar electricity generated, how much of that generation is used directly by common facilities, the applicable electricity tariff, export-credit mechanism, system performance and any applicable charges.

For example, a property with lifts, pumps, treatment equipment and other daytime loads may be able to consume a meaningful portion of solar generation while it is being produced. A property whose common electricity use occurs mainly after sunset may have a different financial outcome even if both properties install the same solar capacity.

This is why proposal comparisons should not rely only on statements such as “this many kW will save this much money.” The generation assumption, self-consumption assumption, applicable tariff and export treatment should all be visible.

Subsidy can improve the economics of an eligible project, but subsidy should not determine the system size. A properly sized system should continue delivering value long after the subsidy has been received.

Not automatically.

A standard grid-connected on-grid solar system is designed to shut down when the utility grid fails. This protects the electricity network and personnel working on it.

Therefore, installing rooftop solar does not by itself mean the society's lifts, pumps or common lighting will continue operating during a power cut.

If backup is an important requirement, the project needs a separate engineering assessment covering critical loads, battery capacity, inverter architecture, backup duration and electrical segregation.

For many apartment communities, the correct decision may be to use on-grid solar primarily for electricity-cost reduction while retaining an existing generator or separate backup arrangement for essential loads. Other properties may justify a hybrid solution. The answer depends on the actual requirement rather than a universal rule.

A good housing-society solar project should resolve governance, engineering, financial and regulatory questions before panels arrive at the site.

The exact sequence can vary according to project category and current regulatory procedure, but the underlying principle should remain the same: approvals and system economics should be planned before installation, not solved afterward.

A lower quoted price does not automatically mean a better solar investment. Apartment solar is a long-term infrastructure decision involving a shared building, shared electricity costs and multiple residents.

The strongest proposal is usually the one that makes the design logic and financial assumptions easiest for the committee and residents to verify.

The core subsidy and Tamil Nadu regulatory framework is state-wide, but every apartment property still needs its own technical and financial assessment.

For a housing society in Coimbatore, Tiruvannamalai or another part of Tamil Nadu, factors such as common-area consumption, tariff category, roof geometry, surrounding buildings, shading, water tanks, structural conditions and local grid feasibility can change the final recommendation.

This is also why genuine local project experience matters. A proposal should not merely state that apartment solar is possible; it should demonstrate how the common loads, roof and electrical connection at that specific property have been evaluated.

For housing societies, the first question should not be “How many panels can we install?” It should be “What solar system makes sense for this community?”

Scaler Solar begins with the common-area electricity requirement and site conditions, then works through system sizing, roof feasibility, design, expected generation, subsidy eligibility, approvals and project economics before the final recommendation is made.

The objective is to make the proposal understandable to both the committee making the decision and the residents whose common expenses and shared property are affected by it.

Policy note: PM Surya Ghar subsidy rules, CFA limits, Tamil Nadu metering provisions, TNPDCL procedures and other regulatory requirements can change. This guide reflects official information reviewed on 19 October 2026. Verify the latest applicable scheme and electricity-service requirements before making a final project decision.