Solar panels for factories — is rooftop solar worth it for your plant?

For most factories, yes — and the arithmetic is not close. Rooftop solar lands at roughly ₹3.5–5 per unit levelised over the plant's life against ₹7.5–9.5 for industrial grid supply, so every unit the plant generates and the factory consumes is bought at about half price for twenty-five years. Two conditions decide whether that arithmetic reaches you. The first is daytime coincidence: solar only pays where the load runs while the sun is up, which is why single-shift manufacturing is the ideal case and a night-shift plant is not. The second is capacity: your DISCOM caps net-metered capacity against sanctioned load, and the distribution transformer has its own headroom, so what you may install is often smaller than what your roof would hold. Where both conditions hold, payback typically lands in the three-to-six year band and the plant runs for two decades after that.

They answer different constraints, and large units increasingly run both. Rooftop is behind the meter: no wheeling charge, no cross-subsidy surcharge, the lowest per-unit cost available to you — and a hard ceiling set by your roof and your sanctioned load. Open access buys power from an off-site plant across the grid: it scales far past what any roof allows, but the delivered cost carries wheeling, cross-subsidy and additional surcharges that vary by state and are revised, and it is a contractual commitment rather than an asset you own. The common answer for a power-hungry plant is a hybrid — rooftop for the daytime base load, open access for the balance. Anyone selling only one of the two will not raise the comparison.

OPEX, RESCO and PPA are three names for one arrangement: a developer funds, owns and maintains the plant on your roof, and you buy the units it generates at an agreed tariff. Under CAPEX you fund it, own it, claim accelerated depreciation and keep every rupee it saves. The engineering is identical — this is a finance decision, not a solar one. CAPEX suits a company with the capital and the tax position to use the depreciation, and over the plant's life it wins because nothing is shared. RESCO suits a company that wants the savings without the capital outlay or the maintenance responsibility. Read the term, the tariff escalation and the buyout clause before comparing headline tariffs: a RESCO rate below your grid tariff is not automatically the better ten-year outcome.

As a working figure at a ₹9/unit blended tariff, a ₹1 lakh monthly bill is roughly 11,000 units — about 90–95 kW of solar if you wanted to offset all of it, or less if your DISCOM caps net metering at your sanctioned load. Size against consumption and rules, not the bill alone; the calculator does this arithmetic for your numbers.

Under net metering it's exported and credited per your DISCOM's banking rules — which differ by state and are tightening in several. Under a captive/behind-the-meter design without export, Sunday generation is curtailed unless you shift load. This single policy detail changes optimal plant size by 10–20% and is exactly the kind of input an EPC should model before quoting.

Pre-engineered sheds usually take ~12–15 kg/m² of additional load comfortably, but older trussed roofs, corroded purlins and asbestos sheets need a structural verdict first. We survey before we design — replacing sheeting or reinforcing purlins is sometimes part of an honest quote, and skipping that check is how plants end up on roofs that can't hold them.

Current C&I turnkey benchmarks run roughly ₹24,000–32,000 per kW installed for rooftop systems (from ₹28,000–32,000/kW at 100 kW to ₹24,000–26,000/kW at 1 MW), varying with structure type, cable runs, inverter class and metering scope. See the detailed breakdowns for 100 kW, 250 kW, 500 kW and 1 MW plants, or run your own configuration in the calculator.

Materially. Businesses can claim accelerated depreciation (40% WDV) on solar assets and input credit treatment depends on how the contract is structured — both improve post-tax payback versus the sticker calculation. We flag the current treatment during proposal; confirm specifics with your CA, as tax positions change.

We do, in-house — net-metering application, CEIG approval and synchronisation. Approvals are our core trade as an MEPF contractor; our published guide on net-metering timelines in UP, Punjab and Haryana reflects filings we actually run, not theory.