Solar PV ROI & Payback Calculator
Calculate your rooftop solar plant’s payback period, 25-year cumulative net savings, IRR, and Levelized Cost of Electricity (LCOE). Modeled for real Indian operating conditions.
1. System & Capital Investment
2. Energy Generation & Aging
3. Electricity Tariff & Consumption Slabs
4. Plant Maintenance (AMC) & Overhauls
25-Year Cumulative Cash Flow & Break-Even Trajectory
| Yr | Gen (kWh) | Tariff (₹) | Gross Savings | Maintenance | Net Annual | Cumulative Position |
|---|
The Engineering Math Behind Solar ROI
1. How does the 4.0 units/kW/day generation formula work?
Across Maharashtra and central India, solar plants receive an average of 4.0 to 4.5 Effective Sun Hours (ESH) per day throughout the year (accounting for monsoon lulls and summer peaks). Multiplying 4.0 units/day by 365 days yields a canonical annual benchmark of 1,460 units per kW of installed solar. For a 5 kW plant, that is 7,300 clean kWh in Year 1.
2. Why does high consumption make solar pay back much faster?
In India, progressive electricity billing means higher slabs carry punitive per-unit rates. For a home consuming ~400 units/month, the blended average rate is ~₹10/unit. But every unit consumed between 301 and 500 units is charged at ₹15.00/unit, and units above 500 cost ₹17.50/unit! When solar cuts your consumption down from 500+ units into the lower slabs, it displaces the most expensive power first.
Frequently Asked Questions
How does 0.75% yearly degradation affect 25-year returns?
Tier-1 monocrystalline panels feature a 25-year linear performance warranty. Degrading at 0.75% annually, a plant that produces 7,300 kWh in Year 1 will still reliably generate approximately 6,090 kWh in Year 25 (over 83% of original generation capacity).
How do tariff and AMC escalation rates impact returns?
Over 25 years, utility grid tariffs and field maintenance costs both grow due to inflation. We provide separate escalation controls (both defaulting to 4.0% per year). While rising electricity tariffs expand your annual avoided-cost savings, AMC escalation realistically accounts for increasing technician wages and operational servicing costs over the plant's 25-year life.
Protect Your 25-Year Solar Investment
A great financial model is only as good as physical rooftop maintenance. Solabrix delivers engineering diagnostics, scheduled washing, earthing maintenance, and rapid problem resolution across Pune.