[2] In a case where Company A sought the payment of electricity charges that had not been claimed by mistake after supplying electricity under the electricity supply contract concluded with Company B, and Company B sought confirmation of the existence of an obligation, the case holding that the lower court erred by misapprehending the legal doctrine in determining that additional electricity charges that Company B shall pay to Company A for 1/2

[2] In a case where Company A sought the payment of the electricity charges that had not been claimed by mistake after supplying electricity under the electricity supply contract concluded with Company B, and Company B sought confirmation of the existence of an obligation, the case holding that the lower court erred by misapprehending the legal doctrine, even though the claim for the electricity charges under the electricity supply contract that the Corporation established effectively with Company B was not permissible against the principle of trust and good faith or the principle of equity, and thus, it is difficult to deem that the amount of additional electricity charges that Company B paid to Company A was reduced to 1/2

1. Restrictions on contractual responsibilities established in a valid manner under the same general principle as the principle of fairness or the principle of good faith may pose a serious threat to the principle of private autonomy or legal stability. As such, in principle, a court is not allowed to reduce part of the performance when a creditor claims performance of the performance of the performance under an effective agreement (see Supreme Court Decision 2012Da64253, Oct. 15, 2015, etc.).

2. After finding the facts as stated in its reasoning, the lower court determined that: (a) the Defendant erred in applying the meter multiples to the Plaintiff when calculating the electric charges against the employee in charge; (b) the Plaintiff cannot be deemed to have caused the error; (c) the Plaintiff trusted the electric charges imposed by the exclusive supplier of electric power; (d) the Plaintiff applied the electric power of the power distribution facility from 400kmW to 350km; and (e) the Defendant applied again the contract power to supply electricity with 350kmW and applied again to the Defendant for the reduction of the electric charges to the Plaintiff; (b) there was no particular cost and time for the construction; and (d) if the Plaintiff was notified of the additional electric charges from the Defendant, it could be inferred that the Plaintiff would have been subject to the imposition of the lower electric charges by construction as above; and (e) the Defendant did not charge the Plaintiff for the increase in the amount of the electric utility charges or the amount of the electric utility charges calculated by the Plaintiff for one year and four months after neglecting inspection of the additional electric charges.

3. However, it is difficult to accept the above determination by the court below for the following reasons.

A. According to the reasoning of the lower judgment, the Defendant sought payment of the charge for the electricity that was not claimed by mistake among the charge for the electricity that was actually supplied to the Plaintiff during the instant period under the terms of the electricity supply contract concluded with the Plaintiff, and this is an effective performance of its duty under the term of the electricity supply contract and a claim for the performance of the other party’

B. Article 76(1) of the former Terms and Conditions of Supply applicable to the electricity supply contract entered into by the Plaintiff and the Defendant provides for the procedure to additionally claim the difference between the once again calculated and the wrong calculated charges, and there is no provision that the difference may be reduced or exempted in the event of the Defendant’s mistake.

C. Even if the Defendant erroneously applied the meter drainage when calculating the electricity fee against the Plaintiff due to the mistake of the employee in charge, even if the Plaintiff trusted the electricity fee imposed by mistake, it appears to be a circumstance to consider the Plaintiff’s assertion and proof of the Defendant’s tort and the damages incurred therefrom, and it does not constitute a change in the terms of the electricity supply contract concluded between the Plaintiff and the Defendant.

D. In light of the aforementioned legal principles, solely based on the circumstances acknowledged by the lower court, it is difficult to view that the Defendant’s claim for electricity charges under the electricity supply contract that was effective to the Plaintiff is not permissible against the principle of good faith and the principle of equity, and thus, the reduction of the electricity charges is possible. Nevertheless, solely on the grounds stated in its reasoning, the lower court erred by misapprehending the legal doctrine on the principle of good faith, thereby adversely affecting the conclusion of the judgment.

4. Conclusion

Therefore, the part of the lower judgment against the Defendant is reversed, and the case is remanded to the lower court for further proceedings consistent with this Opinion. It is so decided as per Disposition by the assent of all participating Justices on the bench.

Justices Lee Ki-taik (Presiding Justice)