6kW Solar System vs 6.6 kW Solar System: Pros, Cons & Best Use Cases

As Indian homeowners look to cut electricity bills in 2025, the decision between a 6kW solar system and a 6.6 kW solar system is more relevant than ever. Though both are ideal for mid-sized homes, understanding the pros, cons, and ideal use cases can help you make the smartest solar investment.

This guide compares both systems based on performance, cost, and practicality.

⚡ Overview of Power Output

SystemDaily OutputMonthly Output6kW Solar System24–26 units720–780 units6.6 kW Solar System26–29 units780–870 units

✅ Key Insight: A 6.6 kW solar system produces about 8–12% more electricity than a 6kW solar system under similar conditions.

✅ Pros of a 6kW Solar System

• ✅ Lower initial cost
• ✅ Requires less roof space (~400–450 sq. ft.)
• ✅ Ideal for homes with <750 units/month electricity usage
• ✅ Short payback period (4–5 years)

❌ Cons of a 6kW Solar System

• ❌ May not cover full demand in larger homes
• ❌ Less future-proof for EVs or new appliances
• ❌ Slightly lower ROI over 25 years compared to 6.6 kW

✅ Pros of a 6.6 kW Solar System

• ✅ Higher power output (up to 90 extra units/month)
• ✅ Better suited for high-consumption households
• ✅ Quicker ROI in many cases (3.5–5 years)
• ✅ Ideal for future upgrades like EV chargers or battery storage
• ✅ Higher net metering benefits due to extra units

❌ Cons of a 6.6 kW Solar System

• ❌ Slightly higher cost (₹20,000–₹30,000 more)
• ❌ Requires more roof space (~450–500 sq. ft.)
• ❌ Not ideal if monthly usage is low (<700 units)

💰 Cost Comparison (2025, India)

SystemApprox. Cost (With Subsidy)6kW Solar System₹1.8 – ₹2.2 Lakhs6.6 kW Solar System₹1.9 – ₹2.4 Lakhs

📝 The difference in upfront cost is minor compared to the long-term value the 6.6 kW system delivers.

🏡 Best Use Cases

Best Use Case for 6kW Solar System:

• 2–3 BHK home
• Power usage <750 units/month
• Budget-conscious households
• Limited roof area

Best Use Case for 6.6 kW Solar System:

• 3BHK+ home with ACs, geysers, or EVs
• Monthly usage above 800 units
• Families with rising electricity needs
• Homeowners wanting better ROI and more savings

📈 Long-Term Savings Difference

Over 25 years:

• 6kW Solar System can save ₹18–₹20 lakhs
• 6.6 kW Solar System can save ₹20–₹22.5 lakhs

✅ The extra investment in a 6.6 kW solar system leads to ₹2+ lakh more in lifetime savings.

📝 Final Verdict

Factor6kW System6.6 kW SystemCostLowerSlightly higherPower OutputGoodBetterRoof SpaceLess neededSlightly moreROI4–5 years3.5–5 yearsFuture ReadyLimitedExcellent

Conclusion:

Both systems are excellent, but if you want more power, faster ROI, and flexibility for future upgrades, the 6.6 kW solar system is the better choice.