The PM Surya Ghar Subsidy Is Paid in Slabs, Not a Percentage — Here Is How That Trips Up Calculators

PM Surya Ghar: Muft Bijli Yojana is the single biggest driver of India's residential rooftop solar demand today, and the subsidy amount it pays is the number every customer asks about first. It is also, surprisingly often, the number online calculators and installer quote tools get wrong — not by a rounding error, but by using the wrong formula entirely.

What the scheme actually pays

The Central Financial Assistance under PM Surya Ghar is paid in fixed slabs, not as a share of system cost: ₹30,000 per kW for the first 2 kW of system capacity, ₹18,000 per kW for the third kilowatt, and a hard cap of ₹78,000 for any residential system 3 kW or larger. A 1 kW system gets ₹30,000. A 2 kW system gets ₹60,000. A 2.72 kWp system — a very common real-world size, since panel wattages rarely divide evenly into whole kilowatts — gets the pro-rated third-kilowatt rate on top of the first two, working out to roughly ₹72,960. Nothing above 3 kW changes the subsidy; it stays capped at ₹78,000 regardless of whether the system is 3 kW or 10 kW. Group housing and RWA installations follow a separate schedule entirely — ₹18,000 per kW up to 500 kW collectively — and should never be quoted against the residential cap.

Why a percentage-based calculator seems reasonable, and isn't

It is easy to see how a percentage shortcut gets built: take a typical cost-per-kWp figure, apply something like "30% subsidy," and the output looks plausible on a demo. The problem shows up the moment the tenant's own price-per-kWp setting differs even slightly from whatever number the calculator was built against — because a percentage of system cost tracks the *installer's price*, not the *government's slab table*. Raise your price and, under a percentage model, the "subsidy" appears to go up with it. That is backwards: the subsidy is a fixed number set by the scheme, entirely independent of what any individual installer charges.

What gets wrong, and in which direction

• At the small end (1–2 kW), a percentage-of-cost model built around a lower assumed price per kWp routinely under-quotes the subsidy by tens of thousands of rupees against what the household is actually owed.
• At the large end (a 10 kW-plus system, common in bigger homes), the same percentage model can over-quote the subsidy substantially, because it never respects the ₹78,000 cap — the cap is the whole point of the scheme's design, and a percentage formula has no way to express a hard ceiling.
• Because the error direction flips depending on system size, there is no single "correction factor" that fixes a percentage-based calculator — the fix is to stop using a percentage at all and implement the actual slab table.

What an accurate calculation actually requires

A correct subsidy figure needs exactly three things: the fixed per-kW rate for the first 2 kW, the pro-rated rate for the third kilowatt (since real systems rarely land on a whole number), and a hard cap applied after both are summed. None of that depends on the price the installer is charging — the subsidy calculation and the pricing calculation are two entirely separate pieces of arithmetic, and a platform that lets a tenant's own pricing setting quietly influence the government's number has a structural bug, not a cosmetic one.

Solset AI's Design Studio and its free public subsidy calculator compute the subsidy from the real slab table — one shared piece of logic used everywhere the number is shown, so a residential quote, a design report, and the calculator itself can never quietly disagree with each other. For the fuller walkthrough of the scheme's disbursal timelines, application volumes, and where installer-side applications typically stall, see our complete PM Surya Ghar guide for EPCs.