☀️ ELECTRICAL

Rooftop Solar PV System Sizing Calculator

Size rooftop solar PV system for India — panels, inverter kW, annual generation and savings. City-wise peak sun hours. IS 16221 / MNRE.

📐 Standard: IS 16221 / MNRE
✅ Free to use
📄 PDF export
📱 Mobile friendly

ℹ️ About This Calculator

India receives 4–6 peak sun hours daily across most of the country, making rooftop solar one of the best investments for commercial and residential buildings. The MNRE (Ministry of New and Renewable Energy) PM Surya Ghar scheme provides subsidies for residential rooftop solar up to 3 kWp. Our calculator determines the optimal system size, panel count, and payback period for your energy demand.

IS 16221 covers the requirements for photovoltaic systems. The PM Surya Ghar Muft Bijli Yojana scheme (2024) provides subsidies of ₹30,000 per kW for first 2 kW and ₹18,000/kW for 2–3 kW for residential connections. Net metering regulations (per CERC 2023 guidelines) allow you to export surplus solar power to the grid and receive credit. For commercial buildings, accelerated depreciation under Section 32 of the Income Tax Act allows 40% depreciation in the first year.

📐 Solar PV Sizing Formula (MNRE / IS 16221)

IS 16221 / MNRE

System Size (kWp):
  kWp = E_daily / (PSH × η_system)

Where:
  E_daily   = Daily energy demand (kWh/day)
  PSH       = Peak Sun Hours for your city
  η_system  = System efficiency (1 - losses)
             = 1 - 0.20 (20% typical losses: soiling, wiring, inverter)

Number of panels:
  N = kWp_required × 1000 / Panel_Wp

Annual Generation:
  E_annual = kWp × PSH × 365 × η_system

Peak Sun Hours by city:
  Rajasthan: 5.8h | Delhi: 5.5h | Chennai: 5.6h
  Mumbai: 5.2h | Bangalore: 5.0h | Kolkata: 4.8h

❓ Frequently Asked Questions

How many solar panels do I need for a 1 kWp system? +
At 400Wp per panel (standard in 2024–25): 1000W / 400W = 2.5 panels → 3 panels for 1.2 kWp. At 540Wp (larger commercial panels): 2 panels for 1.08 kWp. A 3 kWp residential system (eligible for full MNRE subsidy) needs 7–8 standard 400Wp panels and requires approximately 20–25 m² of shadow-free roof area.
What is the payback period for rooftop solar in India? +
For commercial installations at ₹8/kWh electricity tariff: typically 4–6 years. For residential with MNRE subsidy: 5–7 years. System life is 25 years, so the return on investment is 15–20 years of free electricity after payback. Panel degradation of 0.5–0.7% per year means a 25-year-old panel still produces about 85% of original output.
What losses should I assume for solar PV system sizing? +
Typical system losses: soiling and dust (3–5%), temperature derating (3–5%), wiring losses (2–3%), inverter inefficiency (3–5%), shading (0–10% depending on site), module mismatch (1–2%). Total system losses of 15–25% are typical in Indian conditions. Use 20% as a conservative design assumption.
On-grid vs off-grid solar — which is better for India? +
For urban and semi-urban buildings with grid connection: on-grid (grid-tied) with net metering is always preferred. No battery cost, no battery maintenance, simpler system, better ROI. Off-grid with batteries is only justified for remote locations without grid access or for critical backup power. Hybrid systems (grid-tied with battery backup) are now available for buildings wanting both net metering benefits and outage protection.
What is the MNRE subsidy for rooftop solar in 2024? +
Under the PM Surya Ghar Muft Bijli Yojana (2024): ₹30,000/kW for first 2 kW, ₹18,000/kW for 2–3 kW for residential consumers. Maximum subsidy: ₹78,000 for a 3 kWp system. Commercial and industrial installations do not receive MNRE capital subsidy but qualify for accelerated tax depreciation.

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⚠️ Disclaimer: For preliminary engineering design only. Verify all results with a licensed engineer before use. Full disclaimer →

☀️ Solar PV Sizing Calculator
Reference: IS 16221 / MNRE