Rs 156.13 crore refund on hold: APTEL doubts a 2022 corrigendum can reopen NHDC's old tariffs
CERC ordered NHDC to refund Madhya Pradesh Rs 156.13 crore of Secondary Energy Charges after a corrigendum changed a unit of water measurement in the Indira Sagar clearance of 1984. The Appellate Tribunal for Electricity stays the payment direction, finding prima facie that settled tariffs cannot be rewritten retrospectively on that basis.
The Appellate Tribunal for Electricity (APTEL) has stayed a Central Electricity Regulatory Commission (CERC) direction that NHDC Limited refund Rs 156.13 crore to Madhya Pradesh's power purchaser, after finding prima facie that a corrigendum issued in 2022 cannot reopen tariffs settled years earlier.
The order of 2 November 2026 came on NHDC's stay application in Appeal No. 329 of 2026. The bench was Seema Gupta, Officiating Chairperson, and Virender Bhat, Judicial Member.
The appeal itself is yet to be heard. The stay is provisional, and the bench said its observations are prima facie and will not prejudice either side at final hearing.
A water unit corrected after four decades
NHDC runs two hydroelectric projects on the Narmada in Madhya Pradesh: the 1,000 MW Indira Sagar Project (ISP), which reached commercial operation on 25 August 2005, and the 520 MW Omkareshwar Project (OSP), which did so on 15 November 2007.
NHDC is a joint venture of NHPC Limited (51 per cent) and the Madhya Pradesh government (49 per cent). M.P. Power Management Company Limited (MPPMCL) buys its entire output at tariffs fixed by CERC.
CERC fixed Design Energy, Firm Power and tariff for both projects over successive tariff orders. It did so on the basis of Techno-Economic Clearances (TEC) issued by the Central Electricity Authority (CEA), on 22 May 1984 for ISP and 14 December 1993 for OSP.
On 29 March 2022 the CEA issued a corrigendum to the ISP clearance. It said the unit for water utilisation, the parameter 'Q', which had been given in Billion Cubic Metres (BM³), should be read as Million Acre Feet (MAFt).
MPPMCL then petitioned CERC, in Petition Nos. 378/MP/2022 and 220/MP/2022, to revise Design Energy and Firm Power for both projects on that basis.
What CERC ordered in March
By a common order of 30 March 2026, CERC held that Q should have been counted in MAFt and that the corrigendum relates back to the original clearance. It directed revision of Firm Power, Design Energy and consequential tariff for 2010-11 to 2018-19.
It also held MPPMCL's petitions to be within limitation, since the cause of action arose with the corrigendum, and not forum shopping or abuse of process.
The parties were told to reconcile the difference in three months, and NHDC to refund it in 12 equal, interest-free instalments. The reconciled sums are Rs 109.58 crore for ISP and Rs 46.55 crore for OSP, together Rs 156.13 crore, or about Rs 13.01 crore each.
Design Energy for 2019-20 onwards is to be handled in NHDC's pending truing-up petitions for 2019-24.
NHDC: concluded tariffs cannot be reopened
Suparna Srivastava appeared for NHDC. She argued that the corrigendum says nothing about retrospective effect, and that it cannot be called a clerical correction because it changes the technical basis of tariff and creates large liabilities.
She said MPPMCL took part in the tariff proceedings, accepted BM³ for years, and let the tariff orders become final.
NHDC also pleaded res judicata. In its order of 6 January 2022 in the 2019-24 tariff case, CERC had declined to revise the Design Energy at that stage, observing that Firm Power and generation would be reviewed on actual data after the three stages of water utilisation.
It added that the corrigendum was not new and important matter justifying review, that the review limit under CERC's regulations is 45 days, and that MPPMCL had asked only for declaratory relief but was given money.
It further relied on Section 62(4) of the Electricity Act, 2003 and said MPPMCL was pursuing overlapping reliefs before the Madhya Pradesh High Court, which amounted to forum shopping.
On balance of convenience, NHDC said the power purchase costs had already been accounted for and passed through in the annual revenue requirement and retail tariffs, so reconciling accounts retrospectively would have cascading financial and regulatory consequences.
MPPMCL: the formula was NHDC's own
Appearing for MPPMCL, Aashish Anand Bernard said NHDC never challenged the corrigendum. A corrigendum, he argued, relates back to the original document, unlike an amendment, which operates only from its date of issue.
He said the CEA had consulted NHDC before issuing it, and that NHDC itself wrote to the CEA on 2 November 2022 asking about its effective date but never challenged it when the CEA did not reply.
MPPMCL denied seeking a review. The formula for Design Energy came from NHDC, it said, and only the value of Q needed correcting. Limitation ran from the corrigendum of 29 March 2022, and the petitions were filed in August 2022.
It said the revision touched only Secondary Energy Charges, an incentive paid above the approved fixed charges. Total generation was unchanged, and only energy was reclassified between Design Energy and Secondary Energy.
The numbers, as MPPMCL put them: the TEC permits ISP Design Energy of 1,980 million units. NHDC had been computing it between 1,900.93 and 1,423.28 million units, against a range of 1,958.91 to 1,655.89 with Q in MAFt.
For OSP, the TEC figure is 1,166.57 million units. NHDC's computation ran from 865.05 to 736.45, and from 896.44 to 848.77 on MAFt. A lower Design Energy, MPPMCL said, leaves more output counted as Secondary Energy and so a bigger incentive claim.
Corrigendum or addendum?
The bench began with the test for interim relief: a prima facie case, balance of convenience and irreparable injury. The first is indispensable and at least two must be met together.
It then framed what it saw as the real issue:
"whether the letter dated 29.03.2022 can be considered a corrigendum or to be considered an addendum and even if at this stage it is assumed to be in the form of corrigendum, can it alter the concluded tariff determination since FY 2010-2011" (para 21)
A corrigendum, the bench said, is issued to rectify an error, omission or misstatement in the original and heals a defect in the text. An addendum supplements the original. In its words, "a corrigendum cures, an addendum augments" (para 21).
The bench also pointed to functus officio and finality: a regulator cannot alter concluded tariff orders that have been acted upon and under which rights have crystallised. Tariff orders are quasi-judicial determinations, it said, and once trued up or tested on appeal they merge into the regulatory continuum.
Why the stay was granted
The bench took note of several features in the record. The ISP clearance showed the water unit in both MAFt and BM³, while the OSP clearance used MAFt only. The energy calculations, however, used BM³ for both, and MPPMCL had accepted that since commissioning.
The change, though ostensibly clerical, has substantive consequences because it alters the Design Energy computation and therefore tariff. Once tariff orders have been passed, scrutinised and implemented, they "cannot, prima facie, be reopened retrospectively" on a corrigendum, it said (para 23).
It also traced the history. MPPMCL disputed the unit during the 2014-19 tariff case and, by a letter of 17 May 2021, asked the CEA to review the ISP clearance, which led to the corrigendum. CERC on 6 January 2022 found revision unwarranted at that stage.
Yet the March 2026 order re-determined Design Energy for both projects from 2010-11, before the ongoing development stage ended. That, the bench said, would prima facie unsettle vested rights and regulatory certainty.
It found the balance of convenience in NHDC's favour, since both sides had acted for years on the clearance then in force. It noted NHDC says it has started computing Design Energy under the corrigendum prospectively.
Order
APTEL stayed the operation of the order of 30 March 2026 so far as it directs payment of the reconciled amount, pending the appeal. Payments NHDC has already made to MPPMCL are not affected, and status quo is to be maintained on them.
The stay application was disposed of. In the appeal, the respondents have six weeks to file replies and NHDC four weeks thereafter for a rejoinder. After pleadings, the appeal goes on the list of finals.