Rooftop first, then open access, in that order
C and I buyers are moving on both at once and getting the sequence wrong. Why the roof comes first, what open access is actually for, and how to pitch both.
A factory owner who has decided to do something about the power bill usually has two proposals on the table: someone selling a rooftop system and someone selling an open access contract. They are often presented as alternatives, and they are not.
They solve different parts of the same bill, and doing them in the wrong order costs money.
Why anyone is having this conversation
Commercial and industrial consumers pay the highest tariffs in the system and absorb a disproportionate share of every revision. Trade coverage of C and I procurement this year has quoted commercial rates running as high as Rs 15 to 20 a unit in some categories, against diesel generation at Rs 18 to 24 and battery backed supply at Rs 6.5 to 10.
Do not use any of those numbers in a proposal. Use the customer's own bill, because the spread between categories and states is enormous. Use them only to understand why the phone is ringing.
Meanwhile, open access has become practical at a much smaller scale. Policy changes have brought consumers with loads above 100 kW into reach of renewable power through open access, which used to be the preserve of much larger buyers. Maharashtra alone had around 4.8 GW of open access solar by September 2025, roughly 17 percent of the national total.
What the roof does that open access cannot
It sits behind the meter. Every unit generated and consumed on site avoids the full retail tariff including most of the charges layered on top of it. No wheeling, no banking arrangement, no cross subsidy surcharge, no transmission loss.
It is fast. A rooftop system is a matter of weeks. Open access is a contract, an approval process and a construction timeline elsewhere, typically several months.
It uses an asset the customer already owns. The roof is otherwise idle.
It is the cheapest energy the customer will ever buy, precisely because it never touches the network.
The constraint is equally clear: the roof is finite. A factory with a 2 MW load and 400 kW of usable roof cannot solve its problem on the roof, no matter how good the arithmetic is on those 400 kW.
What open access does that the roof cannot
Scale beyond the roof. This is the whole point. It covers the load the roof cannot reach.
Night and monsoon supply, depending on the structure of the contract, which a daytime only rooftop array does not.
A different risk profile. Open access moves the customer into regulatory territory that can change: charges, banking rules and surcharges are all revisable, and the contract lives for years. That is not an argument against it, but it is an argument for reading the state's current open access regulations rather than last year's.
The sequence that works
- Get the load profile before anything else. Not the monthly units, the shape across the day and the week. Which hours carry the demand, when the plant runs, when the shifts change, what happens on Sunday.
- Size the rooftop against the daytime baseline. The portion of load that is reliably present while the sun is up is the part the roof should cover, because every one of those units is consumed on site at full retail value.
- Take the residual to open access, if it is large enough to interest a developer and the state's rules make it worthwhile.
- Consider storage last, for the evening peak and for demand charge management. In Maharashtra, storage is no longer a choice above 100 kW, which is covered in Maharashtra wants a battery on every job above 100 kW.
Selling in that order also happens to be the order that builds trust. You are telling the customer to do the cheap, fast, low risk thing first.
What changed this year that touches both
Four things, and a C and I proposal written in 2025 gets at least two of them wrong.
- GST on solar moved to 5 percent, which changed the landed cost of both. A GSTIN registered buyer reclaims it anyway, so the real effect is on cash flow rather than cost. See GST on solar is 5 percent.
- ALMM List-II applies to open access projects and net metered installations commissioned from 1 June 2026. It does not apply to a purely private behind the meter rooftop system with no net metering. That difference is worth real money and is explained in ALMM List-II is live.
- Storage mandates above 100 kW in Maharashtra, with other states drafting.
- Net metering is narrowing for larger consumers, which strengthens the case for sizing against self consumption rather than against annual units. See net metering is being rewritten.
What the proposal has to show
For a C and I buyer, three things decide it, and none of them is the price per watt.
- Landed cost per unit over the contract life, for each option, on the same page. Rooftop, open access, and the customer's current tariff with a stated escalation.
- What happens to the payback if the tariff does not rise as assumed. C and I buyers test the downside, and an EPC who has already shown it looks like the adult in the room.
- Who carries which risk. Generation shortfall, regulatory change, approval delay, and what your contract says about each.
Payback expectations in this segment are short. Trade coverage this year has put commercial paybacks at 12 to 18 months and industrial at two to three years, with project execution running four to six months. Whether your job lands in that range depends on the tariff the customer actually pays, which is why the bill, again, comes first.
The short version
- Rooftop and open access solve different parts of the bill. Rooftop first, open access for the residual, storage last.
- Rooftop is behind the meter, fast, and avoids network charges entirely. Its limit is roof area.
- Open access scales past the roof and now reaches consumers above 100 kW, but carries regulatory and contractual risk.
- Start from the load profile across the day, not from monthly units.
- ALMM List-II catches open access and net metered projects, not purely private behind the meter rooftop.
- Show landed cost per unit for each option, the downside case, and who carries which risk.
Sources
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