Open access solar for industries — when it beats your roof, and what it really costs
Open access solar lets a factory buy power from an off-site solar plant, delivered over the grid — so the plant can be far larger than your roof. Whether it saves money depends on a stack of state-set charges, the banking rules and your load shape. We engineer rooftop plants ourselves, so we compare the two on your bills and recommend whichever the numbers support — very often both.
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Request an open-access vs rooftop comparison
Four details to start. An engineer reads your connection and consumption, then tells you whether open access, rooftop or both is worth modelling.
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Send my electricity bill on WhatsAppWhat the assessment covers — and what it does not
What an engineer looks at: a suitable system size range for your site; how much of your roof is realistically usable once shading, skylights and walkways are taken out; how much of your consumption falls in daylight hours, because that is what solar can actually offset; an indicative investment range; and the engineering checks that come next — sanctioned-load headroom, roof structure and the DISCOM route for your district.
Assumptions we state rather than hide: generation figures are modelled from regional averages, not measured at your site. Indicative costs are exclusive of GST and exclude roof strengthening, HT-side works, battery storage and statutory fees.
What this is not: not a detailed engineering design, not a guaranteed saving, not an assurance that any approval will be granted, and not a commitment to a site visit. Your connected load is not the same as the solar capacity you can install, and solar offsets energy charges — it does not make an entire bill disappear. Where a number depends on something we have not seen, we will say so rather than assume it.
How open access solar works — and how it differs from rooftop
Under open access a developer builds a large plant elsewhere; you contract for its output and the energy is wheeled to you over the transmission and distribution network. On a rooftop captive plant the generation sits behind your meter and offsets your consumption directly. They answer different constraints: rooftop is cheap per unit and capped by your roof; open access is scalable and contractual.
| Open access solar | Rooftop captive | |
|---|---|---|
| Where the plant sits | Off site, delivered across the grid | Your roof, behind your meter |
| Who can use it | From 100 kW contracted demand under the GEOA Rules, 2022 (historically 1 MW and above); state adoption varies | Any connection, sized within the sanctioned-load rules |
| Size ceiling | Effectively your contracted demand | Usable roof area, structure and sanctioned load |
| What you pay | The PPA rate plus wheeling, transmission, surcharges, banking charges and losses | Your own capital (or a RESCO tariff); no wheeling, no surcharges |
| Tariff certainty | Lower — the charges are revised in tariff orders | High — you avoid the retail tariff, whatever it becomes |
| Banking of surplus | Banking windows have tightened across states | Net-metering rules, state-specific |
| What you end up with | A long-tenor supply contract with termination clauses | An asset you own for its 25-year life |
The charges that decide whether open access solar saves money
The headline on a PPA term sheet is not the price you pay. The landed rate is the PPA rate plus a stack of regulated charges, each set by your state's regulator and each revisable:
- Wheeling and transmission charges — for using the network between the plant and your connection.
- Cross-subsidy surcharge — industrial tariffs cross-subsidise other consumer categories; when a factory moves its supply off the DISCOM, the surcharge claws part of that margin back.
- Additional surcharge — levied on top, by state order.
- Banking charges and banking windows — what happens to units delivered when you cannot use them.
- Losses — the energy that does not arrive.
States have repeatedly raised surcharges when industrial migration hurt DISCOM revenue, and several have narrowed banking into time slots. None of that makes open access a bad deal — large consumers with strong daytime load routinely do well — but it means the saving on the term sheet rests on a charges schedule that is one tariff order away from changing.
The comparison worth making is the delivered cost per unit over ten years, both models, with the open-access case stress-tested for surcharge revisions and banking restrictions. The full reasoning is in our guide to open access versus rooftop captive, and the term itself is defined in the glossary.
Third-party open access or group captive — which structure
Third-party open access PPA
A developer owns the plant and sells you its units. You carry no capital and no plant risk, and you pay the full charge stack on every unit. The contract terms — tenor, escalation, termination, the developer as a counterparty — matter as much as the tariff.
Captive and group captive
You hold equity in the generating plant — alone, or with other consumers in a group captive. Equity participation that meets the statutory tests can waive the cross-subsidy surcharge, often the largest single charge. The tests are legal conditions, so the structure is settled with your legal and finance advisers; the engineering and the load data it rests on are ours.
Whichever structure carries the contract, the funding question is separate: who puts up the capital and who keeps the savings is covered in solar PPA, RESCO or bank loan.
Rooftop first, then open access for the balance
For most industrial consumers the robust order is layered. Fill the roof first, because behind-the-meter units are insulated from the entire open-access charge stack and from banking-rule churn — those savings depend on nothing but the sun and your own load. Then contract open access for the consumption the roof cannot serve, sized against your genuine daytime demand.
Start with what the roof can do: solar panels for factories covers whether the arithmetic reaches your plant, the industrial rooftop solar EPC page covers HT-connected plants, and the 1 MW solar plant cost page shows what a large rooftop costs. Check the cap before anything else with the sanctioned-load calculator.
Who open access suits — and who it doesn't
- Continuous-process plants running flat through daylight hours
- Multi-shift operations that absorb solar as it arrives, without leaning on banking
- Groups able to take a genuine equity stake in a captive plant
The worst candidate is a factory whose consumption is modest, seasonal or evening-weighted: every unit it cannot use as delivered leans on banking provisions that states keep narrowing. The honest first step is a year of consumption data laid against a solar delivery curve — before anyone shows you a term sheet.
An open access solar evaluation, engineered from your bills
- Bill and consumption analysis — your load shape against a solar delivery curve
- Rooftop potential first: usable roof, structure and the sanctioned-load cap
- Open-access eligibility read against your contracted demand and your state's route
- Delivered cost per unit over ten years, both models, stress-tested for surcharge and banking changes
- For the rooftop half: design, DISCOM net-metering and CEIG submissions prepared and filed by us — the DISCOM and the inspectorate decide — then installation and commissioning under our solar EPC contract
Because we engineer the rooftop side ourselves, we have no reason to favour the model that needs less engineering. If the numbers say open access, we will say so.
Open access solar in the states we serve
Open-access approvals, charges and banking are state matters. For each state we serve, the solar policy page carries the net-metering rules and filing route, and the contractor page carries the DISCOM and the electrical inspectorate.
Open access solar — straight answers
Who is eligible for open access solar?
Under the Green Energy Open Access Rules, 2022, consumers with a contracted demand of 100 kW or more can apply for green energy open access. Before those rules the route was historically open to 1 MW and above, and states have adopted the lower threshold at different speeds — so eligibility is checked against your state's current regulations and your own connection, not assumed.
Is open access solar cheaper than rooftop solar?
Per unit, usually not. Rooftop units are consumed behind your meter, so every unit avoids your retail tariff with nothing added on top. Open access adds wheeling and transmission charges, cross-subsidy surcharge, additional surcharge, banking charges and losses to the PPA rate. Its advantage is scale: the plant is not limited by your roof. That is why the usual answer for a power-hungry plant is rooftop first and open access for the balance.
What is group captive solar?
A captive arrangement in which the consumers hold equity in the generating plant they draw power from — with group captive, several consumers share one plant. Equity participation that meets the statutory tests can waive the cross-subsidy surcharge, often the largest single charge, which is why captive structures sit behind most of the open-access deals that survive tariff revisions. The shareholding and consumption tests are legal conditions, so the structure is settled with your legal and finance advisers.
Why is there no open-access saving per unit on this page?
Because it depends on charges your state regulator sets and revises — wheeling, transmission, surcharges, banking — and on your voltage level and load shape. A saving quoted without the current orders for your connection is a today number. The open access savings calculator lets you enter your own landed rate; when we model it for you, we price the current orders for your connection.
Can open access and rooftop solar run together?
Yes, and for a large daytime load it is the common answer: rooftop for the base load behind the meter, open access for the consumption the roof cannot serve. Your sanctioned load bounds what both can register against, so the sizing starts there — and any load enhancement or new HT connection the plan assumes moves at DISCOM speed.
Compare open access with your roof — on your own bills
Send a recent electricity bill and your contracted demand. We model the rooftop first, then the open-access balance, and tell you which half carries the saving.