檢視廠商間是否存在競爭關係是探討廠商行爲是否具有限制競爭效果的關鍵。在公平會2013年處分9家民營電廠聯合行爲一案中，民營電廠在長期購售電合約中是否具有競爭關係更一直是主要的爭點。本文使用台電公司公開發布的機組發電資料，以2017年尼莎颱風造成民營和平電廠輸電塔倒塌事件爲例，檢驗民營電廠間的競爭關係。研究結果發現，和平電廠無法供電的事件，造成其他民營燃氣電廠每小時被台電公司多調度了約350 M Wh的電力，且在合約的非保證時段，和平電廠與其他民營燃氣電廠的移轉率約爲0.45。研究結果拒絕民營電廠間完全不具任何競爭關係的假說。

To evaluate competition among firms, it is important to look at the substitution pattern between the firms. In 2013, the Taiwan Fair Trade Commission (Taiwan FTC) fined 9 independent power producers (IPPs) 6.3 billion NTD for their collusive behavior during their contract negotiation process with the utility company (Taiwan Power Company). The IPPs argued that they did not compete with each other in the electricity generation sector because they were already under long-term contracts with the utility company. In this paper, I use unit-level electricity generation data to examine the substitution pattern between IPPs. Using an exogenous event in which He-Ping Power Plant failed to provide power to the utility because its transmission tower had collapsed due to a typhoon, I examine changes in power supply by other IPPs. I find that the event caused other IPPs to increase the amount of electricity supplied to the utility per hour by 350 MWh. During hours when the take-or-pay clauses did not apply, the diversion ratio between IPPs’ gas-generating units and the He-Ping Power Plant was about 0.45. My results reject the hypothesis that IPPs did not compete with each other in the electricity generation sector.