Open Access vs Captive Rooftop Solar: MIDC Nagpur 5 MW Limit

For CFOs, plant engineers, and factory owners in MIDC Nagpur, solar buying should be judged on usable day energy, delivered cost, and capital risk, not on the headline tariff. This open access vs captive solar Maharashtra note, titled Open Access vs. Captive Rooftop Solar in MIDC Nagpur: Banking Restrictions, CSS/AS Charges & MSEDCL 5 MW Limit, compares on-site captive rooftop solar, off-site group captive solar, and third-party open access for factories in Butibori, Hingna, and Kalmeshwar. The goal is to separate rule facts from project assumptions so each proposal stays auditable.

Which solar procurement route fits a Nagpur factory?

Start by testing rooftop solar against measured daytime demand. Then compare off-site group captive where the roof cannot cover the need. Keep third-party open access as a cash-flow benchmark, especially when management does not want plant assets or SPV equity. This is a screen, not a universal rank: approve the structure with the best risk-adjusted cash flow.

The distinction matters because captive means ownership and use, while open access means grid access. An off-site group captive project therefore also uses open access; the two are not rival legal types. The captive rules still test ownership and use under the Electricity Rules amended in March 2026.

For the investment committee, compare three separate paths:

• On-site captive rooftop: equipment on the factory roof, with roof condition, upkeep, and settlement risk.

• Group captive SPV: equity plus a power contract, with governance and captive-rule checks.

• Third-party IPP PPA: bought power with no captive equity, with close review of delivered charges and legal risk.

Use the same demand forecast, discount rate, escalation, and shutdown plan for all bids. If you do not, model gaps can look like cost gaps.

The MSEDCL 5 MW net-metering limit

MERC's 2023 change lifted the net-metering ceiling to 5 MW or the consumer's contract demand or sanctioned load, whichever is lower. It is not a right for every industrial connection to install 5 MW.

Before you commission a rooftop design, ask the engineer to reconcile approved demand, proposed inverter capacity, grid link needs, and usable roof space. A factory called a 2 MW load still needs its connection papers checked. Peak load and approved connection capacity should not be treated as the same input.

When you compare MSEDCL 5 MW net metering vs open access, require a capacity waterfall for any 5 MW rooftop solar ROI check in a Nagpur factory: roof fit, electrical fit, connection eligibility, and economically absorbable output. The smallest limit should set phase one. Filling the roof is not the goal if the extra output has weak settlement value.

Regulatory timing matters: MERC issued draft rooftop rules in September 2026, then extended the consultation in October. Do not treat draft text as live rules; get a status check before close.

Banking restrictions change the value of solar output

Under MERC's 25 March 2026 review order, solar-hour energy banked during 09:00--17:00 can be drawn only during solar hours. It cannot offset use from 6 PM to 10 PM. That four-hour span is also not the full peak window: the order marks 17:00--24:00 as the peak ToD period. Open-access banking is monthly.

Model consumption by settlement period

Do not value savings by multiplying annual solar output by the factory's top rate. Split generation into direct use, banked credit, and leftover surplus. Apply the right avoided cost to each bucket, then deduct the matching procurement and settlement costs.

For example, a Sunday shutdown should trigger its own surplus case. Ask whether exported energy can be used inside the settlement window, what deductions apply, and what happens to the balance. Keep rooftop and open-access worksheets separate; do not assume the same carry-forward rules.

Evening production requires a separate budget

For underwriting, assign zero evening-offset value to day-banked solar units. A plant that runs furnaces, machining, or other process loads after sunset should keep a separate evening power budget. Moving generation off-site does not fix this timing gap by itself.

If storage is proposed, require a separate case for charging cost, conversion loss, wear, replacement, and dispatch limits. Do not hide battery cost inside a blended solar tariff. Review any production shift plan on its own, including labour and throughput effects.

Landed Cost Comparison Table

A credible green energy open access landed cost for Nagpur needs real bids and an interval bill model. The table below uses formulas where there is no verified project quote. A fixed rooftop or PPA price would create false certainty.

For FY 2026--27, the reviewed HT-I industrial schedule shows ₹8.44/kVAh energy charges plus ₹0.81/kVAh wheeling, for ₹9.25/kVAh before other items. Approved HT industrial third-party CSS is ₹2.07/kVAh.

Define every line item on usable, credited energy, not on gross output. For rooftop ownership, include upkeep, insurance, inverter replacement, and finance cost in R. For open access solar, show which network charges are built into the quoted PPA and which are still payable.

Because HT billing uses kVAh while proposals may quote energy units, require a documented conversion and settlement method. Do not just relabel ₹/kWh as ₹/kVAh. Ask the billing specialist to tie both units to the factory meter data.

For MSEDCL industrial solar tariff analysis in Butibori MIDC, use the actual consumer type and voltage level. A location name is not a tariff type. Keep retained grid demand charges in the whole-factory model instead of assuming they vanish.

Regulatory Burden Matrix

Use this matrix as a diligence checklist, not as a substitute for connection-specific approval. Separate a conditional charge from one that already applies. Ask each bidder to attach the order and explain it in the model.

MERC's review order makes rooftop GSC conditional on statewide rooftop capacity reaching 5,000 MW; the FY 2026--27 HT schedule lists ₹1.42/unit. Confirm rollout and the charge base, rather than assuming immediate use or permanent exemption.

The 2023 framework also separates interim rooftop banking charges from GSC. Avoid stacking both automatically without checking the settlement rule.

For additional surcharge open access MSEDCL proposals, do not copy unsupported assumptions from old bills or petitions. The approved forward revenue schedule records no additional-surcharge revenue for the control period. Still, get written billing confirmation for the proposed deal and include change-in-law allocation in the contract.

Captive equity is an ongoing compliance exposure

The captive solar 26 percent equity rule in Maharashtra must be read with the 2026 national changes: captive users together need at least 26% ownership and 51% annual generation use. SPVs are treated as associations of persons, with updated share-rule language. A user holding at least 26% ownership has a specific exception to that share rule.

Do not read 26% ownership as 26% of project cost. Get the share-capital math, voting rights, ownership records, and allocation method. Assign someone to track changes in shareholding and use before the shareholders' agreement is signed.

If captive checks fail, surcharge and carrying cost can apply. Require reporting rights, cure steps, and contract liability split; a low energy price is no help if the compliance duty is not measured.

Sensitivity Scenario Table: a 2 MW factory load

The following is an illustrative screen, not a generation forecast. Assume a factory runs at 2 MW for ten hours a day over 300 days: annual use is 6 GWh. Assume rooftop output of 1,500 kWh per installed kWp a year, only to show sensitivity.

These percentages compare annual amounts only. They are not guaranteed replacement rates: shutdowns, seasonal output, losses, and settlement limits still apply. Replace the assumed yield with a site-specific engineering estimate before you use the figures in an investment memo.

For Hingna or Kalmeshwar plants that may expand, run separate existing-load and expanded-load cases. Do not use uncertain future demand to justify an immediate long-term minimum offtake duty. Stage capacity where the downside case would otherwise depend on growth.

Executive decision matrix

Use the matrix below after engineering checks and bill simulation. Score rooftop ownership and group captive against the same after-tax NPV, downside cash flow, and liquidity tests. Keep third-party open access in the tender when equity preservation is a hard requirement.

Before approval, require 12 months of bills and interval data, a roof structural review, a charge-by-charge landed-cost model, and legal review of the PPA and any SPV papers. Ask for downside cases covering lower output, late commissioning, charge changes, and early exit.

For MIDC Nagpur factory owners, the choice is simple: use rooftop where the roof and day load justify ownership; use group captive where off-site capacity gives better risk-adjusted economics. Approve neither on headline tariff alone.

Q&A

Q1: Does the 5 MW rooftop limit mean every MIDC Nagpur factory can install 5 MW under net metering?

Short answer: No. The ceiling is 5 MW or the consumer's contract demand or sanctioned load, whichever is lower. A factory must still verify its approved connection capacity, inverter capacity, grid link needs, roof fit, and ability to absorb the output economically. The practical project size should be governed by the tightest limit, not by the headline 5 MW number.

Q2: Why is headline solar tariff not enough for comparing rooftop, group captive, and third-party open access?

Short answer: Headline tariff usually does not capture usable credited energy, banking limits, network charges, losses, CSS, additional surcharge treatment, retained demand charges, finance cost, upkeep, or compliance exposure. The guide recommends comparing all options through a landed-cost and cash-flow model using the same demand forecast, discount rate, escalation, and shutdown plan.

Q3: Can daytime solar banking reduce evening or night electricity bills for a factory?

Short answer: The text advises against assuming that benefit. The cited MERC review order allows users to draw solar-hour energy banked during 09:00--17:00 only during solar hours and prohibits counting it as an offset for evening use, such as from 6 PM to 10 PM. Plants with furnaces, machining, or process loads after sunset should keep a separate evening power budget.

Q4: When is group captive more suitable than on-site rooftop solar?

Short answer: Group captive becomes relevant when the factory has stable daytime demand but the roof is limited, not fit, or unable to meet the desired eligible use. However, it requires equity participation, governance review, captive compliance monitoring, and a delivered-cost analysis that includes network charges, losses, banking treatment, and the cost of equity.

Q5: What documents should management require before approving a solar procurement route?

Short answer: The guide recommends at least 12 months of bills and interval data, a roof structural review, a charge-by-charge landed-cost model, connection-specific rule confirmation, and legal review of the PPA and any SPV papers. It also recommends downside cases for lower output, late commissioning, charge changes, and early exit.