Five parts, and one of them decides whether the subsidy is legal.
Most quotes list a wattage and a brand. These are the five things that actually determine what you get, in the order they will matter to you.
Modules
12 years product, 27 years performance to 87.4%540–580 Wp monocrystalline half-cut, ALMM-listed, DCR cells
DCR — domestically manufactured cells — is not a preference, it is the condition for claiming the subsidy at all. A vendor offering you a cheaper non-DCR module and a subsidy is offering you a problem.
Inverter
7 years, extendable to 10String inverter, 97.5% Euro efficiency, 2 MPPT, Wi-Fi monitoring
This is the part that fails first. Budget for replacing it around year 12 and be suspicious of anyone whose 25-year saving figure does not.
Mounting
10 years against corrosionHot-dip galvanised MS, 2.5 mm, ballasted or chemically anchored
On an RCC roof we prefer ballast to drilling. If we must anchor, we do the waterproofing ourselves and we warrant it — most quotes leave that to you and your monsoon.
Cable & protection
5 yearsSolar DC cable, DC SPD, AC SPD, earthing to 2 electrodes
The cheapest place to cut a corner and the one that burns houses down. Ask any quote what surge protection it includes; most say nothing because they include nothing.
Meter
DISCOM'sBidirectional net meter, supplied and installed by the DISCOM
Not ours to sell. If a quote has a line item for the net meter, ask why.
What we would put on a roof, by what you actually use.
| Monthly units | We would fit | Roof needed | Cost | Subsidy | You pay | Payback |
|---|---|---|---|---|---|---|
| 150 | 1.5 kW | 150 sq ft | ₹87,000 | − ₹45,000 | ₹42,000 | 5.2 yr |
| 250 | 2.5 kW | 250 sq ft | ₹1,37,500 | − ₹69,000 | ₹68,500 | 4.6 yr |
| 350 | 3 kW | 300 sq ft | ₹1,65,000 | − ₹78,000 | ₹87,000 | 4.2 yr |
| 500 | 4.5 kW | 450 sq ft | ₹2,29,500 | − ₹78,000 | ₹1,51,500 | 4.7 yr |
| 700 | 6.5 kW | 650 sq ft | ₹3,12,000 | − ₹78,000 | ₹2,34,000 | 4.9 yr |
| 900 | 8.5 kW | 850 sq ft | ₹4,08,000 | − ₹78,000 | ₹3,30,000 | 5.3 yr |
Every figure in that table is computed from the same model as the estimator — a light water-tank shading, a fortnightly wash, 0.5% a year of degradation and an inverter replaced in year 12. Nothing in it is a headline number we would then walk back at the site visit.
