G.R. No. 221709 - National Power Corporation vs. Delta P, Inc.

Delta P, Inc. (Delta P), an independent power producer, assumed operations of a generating plant in Puerto Princesa City previously owned by Paragua Power Corporation (PPC).
Prior to Delta P’s takeover, PPC had an existing Power Purchase Agreement (PPA) with the petitioner, National Power Corporation (NAPOCOR), whereby NAPOCOR agreed to purchase the electricity generated by PPC.
The purpose of the PPA was to ensure the supply of electricity to the consumers of Palawan Electric Cooperative, Inc. in Puerto Princesa City and to nearby towns (Narra, Aborlan, and Quezon, Palawan).

After Delta P took control of the generating plant, it sought to have NAPOCOR direct payment to it for the operation of the plant.
NAPOCOR, however, refused to make payments to Delta P on the ground that PPC was the party contracting under the PPA.
The impasse led Delta P to advise NAPOCOR that it could no longer operate the power station because of insufficient funds.

On February 26, 2003, NAPOCOR Vice-President Lorenzo S. Marcelo issued a memorandum requesting approval from NAPOCOR President Rogelio M. Murga to supply fuel and pay for manpower services at PPC’s generating plant.
The action was prompted by an imminent power shortage in Puerto Princesa City, allegedly caused by Delta P’s difficulties in producing the required electricity due to a lack of bunker fuel.
President Murga approved the memorandum, leading Marcelo to inform Delta P on March 7, 2003, that NAPOCOR would supply the fuel and cover manpower salaries temporarily until Delta P resolved its internal issues.

On March 12, 2003, Delta P filed a collection action (Civil Case No. 3766) against NAPOCOR, asserting its right to collect payment for the electricity “off-taken” by NAPOCOR.
On July 15, 2003, the Regional Trial Court (RTC) ruled in favor of Delta P, applying doctrines of accion in rem verso and unjust enrichment, and ordered NAPOCOR to pay an amount calculated from December 2002 to June 2003.
The RTC’s decision prescribed a payment of PHP87,944,215.67 (after billing adjustments) and became final and executory, leading to its implementation.

On July 30, 2003, following the RTC decision, NAPOCOR issued a Notice of Termination of its fuel supply, emphasizing that no further supply was justified after payment of the adjudged amount.
Despite intentions to cease the supply, the parties later reached an agreement for Delta P to continue generating and supplying electricity, with NAPOCOR undertaking the payment of monthly invoices.
On December 4, 2003, NAPOCOR issued Debit Memo S1-03-12-0041, deducting PHP24,449,247.36 from Delta P’s account for alleged incremental fuel costs incurred from February 25, 2003 to June 25, 2003.
Delta P countered by filing a sum-of-money case, arguing that NAPOCOR’s unilateral deduction was invalid, noting that previous invoices did not include fuel cost components.
The RTC later ruled in favor of Delta P by declaring the debit void and illegal, further ordering NAPOCOR to pay the deducted amount plus interest and attorney’s fees.
The Court of Appeals (CA) affirmed the RTC’s decision, and NAPOCOR’s subsequent motions were dismissed, prompting the petition for review on certiorari before the Supreme Court.

Whether NAPOCOR’s act of supplying fuel to Delta P was gratuitous in nature—a donation executed by an act of liberality—or whether it implied an obligation for reimbursement.

Whether Delta P is liable to reimburse NAPOCOR for the fuel supplied, particularly when considering NAPOCOR’s claim that a post-audit (based on the fuel cost formula stated in the PPA with PPC) gave rise to incremental costs.
Whether such post-audit adjustments constitute a supervening event that could justify unilateral deductions despite the final and executory nature of the RTC judgment in Civil Case No. 3766.