📋 Solar Panels Needed — Quick Reference (India 2026)
Monthly Bill
Units/Month
System Size
400W Panels
Roof Area
Cost (after subsidy)
₹1,000
~143
1.5 kW
4 panels
~110 sq ft
₹35,000–₹45,000
₹1,500
~215
2 kW
5 panels
~140 sq ft
₹60,000–₹80,000
₹2,000–₹2,500
~285–360
3 kW
7–8 panels
~200 sq ft
₹97K–₹1.3L
₹3,000
~430
4 kW
10 panels
~280 sq ft
₹1.5L–₹1.8L
₹4,000–₹5,000
~570–715
5–6 kW
13–15 panels
~380 sq ft
₹2.0L–₹2.6L
₹7,000+
1000+
8–10 kW
20–25 panels
~550 sq ft
₹3.5L–₹4.5L
* Based on ₹7/unit tariff, 5.0 peak sunshine hours, 400W panels. Cost after ₹78,000 PM Surya Ghar subsidy.
Frequently Asked Questions
How many solar panels for a 3 kW system?
A 3 kW system needs 7–8 panels of 400W each (3000W ÷ 400W = 7.5, round up to 8). If you use 440W panels, you need 7 panels. Premium 545W panels need only 6 panels. More watt-per-panel = fewer panels but higher cost per panel.
How much roof space do I need for solar panels?
Each 400W solar panel requires about 25–30 sq ft of usable roof area including mounting clearance gaps. For a 3 kW system (8 panels): 200–240 sq ft. A standard Indian terraced roof of 600 sq ft can accommodate up to 6 kW (15–16 panels). Sloped/RCC roofs need slightly more clearance between rows.
Should I get 400W or 545W solar panels?
Both are good. 400W panels: wider availability, cheaper per panel, more vendors. 545W (bifacial/HJT): fewer panels needed, better in low-light, higher efficiency (21%+ vs 20%), but cost ₹2–4 per Watt more. For roof-limited installs, 545W makes sense. For standard roof sizes, 400W is more economical.
Can I add more panels later to expand my system?
Yes, most inverters support expansion. String inverters can be expanded by adding more panels to the array (up to their rated capacity). Hybrid inverters are the easiest to expand. Always size your inverter 10–20% larger than current panel capacity if you plan to expand.