A solar developer who let one adverse order stand without appeal found out, two petitions and two years later, that the issue it thought it could reopen had already been closed for good. The Appellate Tribunal for Electricity has set aside a Haryana Electricity Regulatory Commission order that had revived Siwana Solar Power Projects Ltd.'s claim to a higher tariff for its 5 MW plant, holding that the point was res judicata.
The dispute traces back to a 2024 petition, Petition No. 26 of 2024, in which Siwana asked HERC to restore a tariff of Rs 6.44 per kWh and to pay the difference over the Rs 5.68 rate it had actually been receiving. HERC dismissed that petition on 12 November 2024, holding the claim barred by res judicata. Siwana did not appeal that dismissal.
Instead, in 2025 Siwana filed a fresh petition, Petition No. 78 of 2025, seeking substantially the same relief dressed up differently. This time HERC took a different view of its own earlier order. In May 2026 it held that an earlier settlement between the parties covered only dues up to March 2019, and on that reasoning it directed the Haryana Power Purchase Centre to pay Siwana Rs 6.44 per kWh prospectively, along with the differential amount and interest at 9.15 percent. The Haryana Power Purchase Centre appealed that order to APTEL.
APTEL's answer was straightforward. The tribunal held that the question of what tariff Siwana was entitled to had already been finally decided in the 2024 proceedings, and that decision was never challenged. A party that lets an adverse order attain finality cannot get a second bite at the same question merely by filing a fresh petition and hoping the regulator reads the facts differently the second time around. Because HERC's November 2024 order went unchallenged, the Rs 5.68 per kWh rate it upheld remained the binding tariff, and the May 2026 order purporting to revive Rs 6.44 could not stand.
The underlying settlement adds a layer anyone tracking this line of disputes should keep in view. Siwana had at an earlier stage accepted a settlement covering outstanding amounts up to March 2019, and that settlement and the proceedings around it had themselves already been upheld by the Supreme Court. HERC's May 2026 order tried to carve out room beyond that settlement by treating it as time-limited, but APTEL's res judicata finding effectively closed that door regardless of how the settlement's scope was read. A regulator cannot resurrect a claim by reinterpreting the scope of its own earlier, unappealed order years after the fact, particularly once a higher court has already blessed the arrangement the parties reached.
For power sector lawyers, the practical point is less about solar tariffs specifically and more about litigation discipline generally. A regulator's finding of res judicata is not a technicality to be sidestepped by repackaging the same relief in a new petition with a slightly different theory attached. Once an order attains finality because no appeal was filed, that finality binds the regulator on any later petition raising the same question, and a developer gambling on the regulator taking a second, more generous look at an old dispute risks losing the tariff fight twice over, first before the regulator's second order and then again before the appellate tribunal.
Developers sitting on unfavourable regulatory orders they chose not to appeal should treat this ruling as a caution rather than an opportunity. Filing a fresh petition years later, hoping a differently constituted bench or a differently framed settlement argument will produce a better outcome, invites exactly the kind of appellate reversal Siwana now faces. The time to fight a tariff finding is the appeal window that follows it, not a second petition built around the same underlying facts years after the first order has quietly become final. Haryana's power purchase agencies, and utilities elsewhere watching this line of cases, now have a clean appellate precedent to invoke whenever a generator tries exactly this manoeuvre again.