Apartment / flat solar guide — RWA options, group net metering, Chennai/Coimbatore case studies

**Why individual flat solar is limited:** rooftop is common property owned by RWA/society. Individual flat owner cannot claim exclusive roof rights without RWA vote. Balcony solar limited to 200-400W (single panel + micro-inverter) — enough for phone chargers, not real bill impact.

**Option 1 — Common area solar (most popular, easiest):** 15-50 kW system powers common area loads only — corridor lighting, elevator, pumps (water + STP), gate, security cameras. Bill reduction 60-90% on common area electricity. RWA maintenance fee direct impact.

**Common area cost math (25-flat mid-rise Chennai example):** common area monthly bill ₹28,000. 20 kW rooftop solar generates 2,600 units/month, offsets 90% → new bill ₹3,000. Monthly saving ₹25,000 = ₹3L/year. System cost ₹9.5L (net after depreciation ₹7.6L for a private ltd RWA — treated as commercial). Payback 2.5 years.

**Option 2 — Group Net Metering (GNM):** single large solar system (100-500 kW), generation credits distributed pro-rata to participating flat owners' individual TNEB accounts. Each flat's individual bill reduced.

**GNM eligibility TN 2026:** min 20 flats participation + roof capacity 3 kW/flat + all flats on same TNEB feeder (usually within one apartment). Regulatory framework TNERC gazette Nov 2024, 40+ pilot apartments Chennai + Coimbatore approved 2025-26.

**GNM cost math (60-flat luxury Coimbatore project):** 180 kW system serves all 60 flats. Each flat gets 3 kW share generation (~360 units/month). Individual TNEB bill drops ₹2,500-3,500/month per flat. Total system cost ₹78L, per-flat contribution ₹1.3L over 5-year EMI scheme. Individual flat payback 3.5 years.

**Option 3 — Virtual Net Metering (VNM):** solar system located off-apartment premises (ground-mount farm 20-30 km away), credits transferred to participating flat accounts via TNEB back-office. Enables apartments with shaded/small rooftops to still benefit.

**VNM status TN 2026:** framework finalized August 2025, first commercial VNM projects Chennai IT corridor apartments Q4 2025. Adoption slow — regulatory complexity + rooftop-first preference. Best for 100+ flat mega-projects with poor roof access.

**Option 4 — ESCO model (Energy Service Company):** SVN or third-party installs at own cost, RWA pays monthly for solar-generated units at 60-70% of TNEB rate for 7-10 years, then system ownership transfers to RWA free. Zero capex for society.

**ESCO cost example (100-flat Chennai society):** ESCO installs 60 kW common area system worth ₹28L. RWA pays ₹4/unit × 8,000 units/month × 84 months = ₹27L over 7 years. Post-year 7 free electricity 18+ years. Cash-flow positive from month 1 (RWA save 30-40% on common area bill immediately).

**Governance requirements (RWA level):** (1) Special general body meeting approval — 2/3rd majority typical. (2) Roof-use no-objection formalization + affidavit. (3) TNEB HT feeder capacity check (LT connection may need upgrade for 50+ kW). (4) Municipal building approval (usually not needed for < 20% roof cover). (5) Fire NOC for 50+ kW.

**Structural feasibility check:** roof load capacity 15-25 kg/sq m needed. Modern RCC roof easily supports. Old apartments (pre-2000) need structural engineer sign-off — column loading + terrace slab reinforcement assessment. SVN offers structural audit report free during quote.

**Common objection handling:** 'Roof leaks after install?' — SVN waterproofing warranty 5-year backed by rubberized coating + drip caps at every mount penetration. 'What if 2-3 flats disagree?' — GNM allows voluntary participation (non-participating flats unaffected). 'Insurance impact?' — solar insurance ₹8k-25k/year addition, RWA maintenance-fund-funded.

**SVN apartment solar portfolio:** 45+ Chennai + Coimbatore apartments (2022-2026). Reference sites: 8 residential complexes in Anna Nagar, 12 in OMR, 6 in Race Course Coimbatore. Free RWA meeting presentation + roof survey + custom cost-benefit report.

**Recommended pathway for interested RWA:** step 1 — SVN free site visit + roof audit + electricity bill 6-month analysis. Step 2 — RWA committee presentation (SVN provides). Step 3 — general body vote. Step 4 — vendor selection + financing model choice (capex/EMI/ESCO). Step 5 — TNEB feeder application + install 60-90 days. Step 6 — commissioning + monitoring app training.