SolarSavings
How the Solar Cost & Payback Modeling Engine Works
The SolarSavingsHub Cost Explorer utilizes a multi-variable algorithmic model to calculate the financial return on investment (ROI) of grid-tied residential rooftop solar in India. Rather than presenting generic averages, our algorithm dynamically couples local solar irradiance data with state-specific retail electricity tariffs and government subsidy structures.
1. Core Financial Payback Equations
The system determines your capital break-even timeline using the levelized net cost formula:
Monthly Solar Energy Output (kWh) = System Capacity (kW) × 4.2 Peak Sun Hours × 30 Days × 0.85 (Derating Factor)
Monthly Financial Savings (₹) = Monthly Output (kWh) × Peak Tier Electricity Slab Tariff (₹/kWh)
Payback Period (Years) = Net Capital Investment / (Annual Financial Savings - Annual O&M Expenses)
2. State-Wise Economic Benchmark Matrix
Rooftop solar economics differ dramatically across state lines based on local DISCOM tariffs and state supplementary incentives:
| State / Region | Gross EPC Cost | Central Subsidy | State Grant | Net Outlay | Monthly Bill Savings | Payback Horizon |
|---|---|---|---|---|---|---|
| Maharashtra | ₹1,55,000 | ₹78,000 | ₹0 | ₹77,000 | ₹4,200 / mo | 3.2 Years |
| Uttar Pradesh | ₹1,50,000 | ₹78,000 | ₹30,000 | ₹42,000 | ₹2,700 / mo | 2.9 Years |
| Gujarat | ₹1,45,000 | ₹78,000 | Priority feed-in | ₹67,000 | ₹2,950 / mo | 3.5 Years |
| Delhi (NCT) | ₹1,55,000 | ₹78,000 | ₹3/u GBI | ₹77,000 | ₹3,600 / mo | 3.1 Years |
| Karnataka | ₹1,52,000 | ₹78,000 | ₹0 | ₹74,000 | ₹2,900 / mo | 3.8 Years |
| Other States | ₹1,50,000 | ₹78,000 | Varies | ₹72,000 | ₹2,800 / mo | 3.6 Years |
Key Factors Influencing Your Financial Return
- Connected Sanctioned Load: Your solar capacity cannot exceed 100% of your sanctioned load without applying for a load enhancement with your utility.
- Shadow Analysis: Parapets, lift rooms, and nearby trees casting shadows during the 9:00 AM to 3:00 PM peak generation window can reduce output by up to 30%. Elevated mounting structures mitigate this issue.
- Degradation Rate: Modern Tier-1 Mono PERC panels experience ~1% degradation in Year 1 and 0.5% annually thereafter, retaining > 84% output at Year 25.
Frequently Asked Questions (FAQ) on Solar Cost Estimation
Is a 3 kW solar system sufficient to run air conditioning?
Yes. A 3 kW solar plant produces 12 to 15 kilowatt-hours (units) daily. A modern 1.5-ton 5-star inverter AC consumes about 1.1 to 1.3 units per hour of continuous compressor run-time, meaning your 3 kW system produces enough energy to run the AC for 8 hours daily alongside standard lighting, ceiling fans, and a refrigerator.
Does the gross price include the bi-directional net meter?
In most states, the turnkey EPC quote includes liaisoning and net meter procurement. However, certain DISCOMs bill a separate statutory meter testing fee (typically ₹1,500 to ₹3,500) on your utility bill.
Can I expand my solar system capacity in the future?
Yes, provided your roof space and sanctioned connected load permit. However, government subsidies under PM Surya Ghar are only provided once per residential consumer connection (up to the 3 kW maximum cap of ₹78,000).