The assumptions behind every number here
- Specific generation: 1,480 kWh per kWp per year (≈4.05 kWh/kWp/day), typical of a 5.2–5.5 kWh/m²/day irradiance band at a 78% performance ratio.
- Turnkey prices: ₹70,000/kW at 3 kW, ₹65,000/kW at 5 kW, ₹58,000/kW at 10 kW, ₹45,000/kW at 50 kW, ₹42,000/kW at 100 kW — GST inclusive.
- Offset tariff: ₹7.50/kWh residential, ₹9.00/kWh commercial.
- Central subsidy applied to residential 3 kW and 5 kW only (₹78,000 cap); no state top-up assumed.
- Simple payback, no tariff escalation, no financing cost, no accelerated depreciation.
Benchmark table
| Size | Annual yield | Net cost after subsidy | Year-1 saving | Simple payback |
|---|---|---|---|---|
| 3 kW residential | 4,440 kWh | ₹1,32,000 | ₹33,300 | ≈4.0 years |
| 5 kW residential | 7,400 kWh | ₹2,47,000 | ₹55,500 | ≈4.5 years |
| 10 kW residential | 14,800 kWh | ₹5,80,000 | ₹1,11,000 | ≈5.2 years |
| 50 kW commercial | 74,000 kWh | ₹22,50,000 | ₹6,66,000 | ≈3.4 years |
| 100 kW commercial | 1,48,000 kWh | ₹42,00,000 | ₹13,32,000 | ≈3.2 years |
Why commercial payback beats residential
Commercial systems offset a higher tariff (₹9.00 vs ₹7.50) at a lower cost per kW (₹42,000 vs ₹70,000) — a roughly 2× swing in economics that has nothing to do with panel efficiency. Accelerated depreciation shortens it further.
Tariff escalation changes the story
The table uses a flat tariff, which understates lifetime returns. At 5% annual tariff escalation, the 5 kW system's cumulative 25-year saving rises from about ₹13.9 lakh to roughly ₹26.5 lakh, and payback shortens by around six months. Every SolvSolar proposal renders this as a cumulative savings arc on the cover page so the client sees the escalation effect rather than a single flat number.
What moves payback most, in order
- The tariff slab being offset — a consumer on ₹11/kWh pays back nearly twice as fast as one on ₹6/kWh at the same system size.
- Self-consumption share under net billing — where exports are credited below retail, daytime consumption is worth far more than export.
- Cost per kW, which falls roughly 40% from 3 kW to 100 kW purely on scale.
- Subsidy eligibility, worth up to ₹78,000 but only for residential connections.
- Shading and soiling losses — a 10% performance ratio gap adds roughly half a year to payback.
Use your own numbers
These are benchmarks, not quotes. The SolvSolar sandbox takes the client's actual monthly bill, tariff, roof type and state irradiance and returns the sized system, year-one saving and payback in about 45 seconds — then turns it into a branded four-page proposal with the same maths on the Financial Plan page.