The Arunachal Pradesh Electricity Regulatory Commission (APSERC) has issued the draft Deviation Settlement Mechanism and Related Matters Regulations, 2025, to establish a commercial mechanism to ensure grid users’ adherence to scheduled electricity drawal and injection and maintain grid security and stability.

The regulations apply to all sellers with installed capacity of 1 MW and above connected to the intrastate transmission system (InSTS), including renewable energy, except wind and solar open access generators and captive generators.

It also applies to all buyers, including distribution licensees, deemed distribution licensees, and full open access consumers connected to the intrastate transmission system.  Partial open access consumers (even on InSTS) and all open access consumers on the distribution network are settled under the Open Access Regulations.

Stakeholders can submit their feedback by December 31, 2025.

Computation of Deviation

A deviation in a time block for general sellers will be computed as follows:

Deviation-general Seller (DGS) (in MWh) = [(Actual injection in MWh) – (Scheduled generation in MWh)].

Deviation-general Seller (DGS) (in %) = 100 x [(Actual injection in MWh) – (Scheduled generation in MWh)] / [(Scheduled generation in MWh)].

A deviation in a time block for wind-solar (WS)  sellers will be computed as follows:

(a) For the period from the date of commencement of these regulations to March 31, 2026

Deviation-WS seller (DWS) (in MWh) = [(Actual Injection in MWh) – (Scheduled generation in MWh)];

Deviation-WS seller (DWS) (in %) = 100 x [(Actual Injection in MWh) – (Scheduled generation in MWh)] / [(Available Capacity)];

(b) For the period from April 1, 2026

Deviation-WS seller (DWS) (in MWh) = [(Actual Injection in MWh) – (Scheduled generation in MWh)];

Deviation-WS seller (DWS) (in %) = 100 x [(Actual Injection in MWh) – (Scheduled generation in MWh)] / [(X% of Available Capacity) + (100-X) % of Scheduled Generation):

The X’ will be determined by the Commission through separate orders after public consultation.

Deviation in a time block for buyers will be computed as follows:

Deviation – Buyer (DBUY) (in MWh) = [(Actual drawal in MWh) – (Scheduled drawal in MWh)]. Deviation – Buyer (DBUY) (in %) = 100 x [(Actual drawal in MWh) – (Total Scheduled drawal in MWh)] / [(Scheduled drawal in MWh)].

Normal Rate of Charges for Deviation

The normal rate (NR) of charges for deviation for a particular time block will be the highest of (A), (B), or (C), where (A), (B), and (C) are as follows:

(A) The weighted average ACP (in paise /kWh) of the integrated day-ahead market (DAM) segments of all the power exchanges.

(B) The weighted average ACP (in paise /kWh) of the real-time market segments of all the power exchanges.

(C) The sum of:

(a) 1/3 [weighted average ACP (in paise/kWh) of the integrated DAM segments of all the power exchanges]

(b) 1/3 [weighted average ACP (in paise/kWh) of the real-time market segments of all the power exchanges]

(c) 1/3 [ancillary service charge (in paise/kWh) computed based on the total quantum of Ancillary Services (SRAS UP and TRAS UP) deployed and the net charges payable to the ancillary service providers for all the regions]: provided that in case of non-availability of ACP for any time block on a given day, ACP for the corresponding time block of the last available day will be considered.

Charges for Deviation

Charges for deviation, in respect of a general seller (other than RoR generating station and a generating station based on municipal solid waste) will be as under:

Deviation charges, in respect of a general seller being a RoR generating station, without any linkage to grid frequency, are as follows:

Charges for deviation, in respect of a general seller being a generating station based on municipal solid waste and without any linkage to grid frequency, will be as under:

Charges for deviation, in respect of a WS Seller, including such generating stations aggregated at a pooling station through a qualified coordinating agency (QCA), will be as follows:

For standalone energy storage systems (ESS), deviation charges will be the same as those applicable to general sellers, excluding run-of-river generating stations and those based on municipal solid waste.

When the ESS is in charging mode, any overdrawal from the grid will be treated as under-injection, while underdrawal will be treated as over-injection, with deviation charges settled accordingly.

In the case of an ESS being a standalone pumped hydro storage project, the deviation charges and the formula for computation during the charging period will be aligned with those applicable to a WS seller being a generating station based on solar sources.

For WS generators with ESS connected at the same interconnection point, the deviation charges can be one of the following:

• Deviation charges applicable to the WS generator category during periods when the solar, wind, or hybrid generating station is injecting power.

• Deviation charges applicable will be equivalent to charges applicable to the ESS is injecting power
• Deviation charges applicable to a standalone ESS for drawal by BESS based on the scheduled drawal from the grid.

Each generator and ESS must be equipped with a special energy meter to capture individual actual injection and drawal data accurately.

Charges for Deviation, in respect of a Buyer, will be receivable or payable as follows:

Charges for the injection of infirm power will be zero, except in the cases specified under a general seller being a RoR generating station, and a general seller being a generating station based on municipal solid waste.

If infirm power continues to be scheduled after the successful completion of the trial run, deviation charges for any variation from the scheduled infirm power will be as applicable for a general seller.

When the system frequency exceeds 50.05 Hz, the charges for the injection of infirm power or for the deviation of scheduled infirm power after the trial run due to over-injection by a general seller will be zero.

Deviation charges for drawal of start-up power before the commercial operation date of a generating unit, or for drawal of power to run auxiliaries during the shutdown of a generating station, will be payable at the reference charge rate or the contract rate.

In the absence of either, the rate will be determined based on the weighted average area clearing price of the Day-Ahead Market segments across all power exchanges for the respective time block.

In the event of a forced or partial outage of a seller, deviation charges will be levied at the reference charge rate for up to eight time blocks, or until the seller’s schedule is revised, whichever occurs earlier.

Payment Schedule

Payment of deviation charges has high priority, and the concerned state entity must pay the indicated amount within ten days of the SLDC issuing the statement of charges for deviation into the state deviation pool account. The state entity must make payment irrespective of any mistake or error in the bill, and the SLDC will rectify any revision or modification on account of such mistake or error in subsequent bills of the entity concerned.

If payment is delayed beyond 10 days from the date of issue of the statement by the SLDC, the defaulting State Entity must pay simple interest at 0.04% for each day of delay.

All payments to entities entitled to receive any amount on account of deviation charges must be made within two working days of receipt of payments in the state deviation pool account. In case of delay in payment into the state deviation pool account and associated interest, if any, beyond twelve days from the date of issue of the statement of charges for deviations.

State entities receiving payment for deviation or interest will be paid from the balance available in the state deviation pool account, and if the balance is insufficient, payment will be made on a pro rata basis from the available balance.

The liability to pay interest for delay in payments into the state deviation pool account will continue until the interest is fully paid, irrespective of whether constituents entitled to receive payments have been paid from the state deviation pool account in part or in full.

All sellers and buyers who, at any time during the previous financial year, failed to make payment of charges for deviation within the specified time must open a letter of credit (LC) equal to 110% of their average payable weekly liability for deviations in the previous financial year, in favor of the SLDC, within a fortnight from the date these regulations come into force.

If a regional entity fails to pay the deviation charges into the Deviation and Ancillary Service Pool Account within ten days, the State Load Despatch Centre can encash the LC to cover the default amount. The regional entity must then replenish the LC within three days.

The Central Electricity Regulatory Commission issued its Deviation Settlement Mechanism and Related Matters Regulations in August last year.

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