電子資源對大學圖書館使用者是最直接便捷的資訊取用途徑，且認為是圖書館應提供的重要服務。然而電子資源價格昂貴，大學經費日益緊縮，在有限的資源下，只依據使用者需求之概念性價值認定，圖書館難以在母機構爭取合理的經費訂購電子資源。若能分析電子資源的成本效益，證明其可為研究者及校方創造實際的價值，將有助於圖書館在經費預算上的爭取。本研究以南台科技大學圖書館為例，利用三種評估方法計算大學圖書館在電子資源的成本效益：一是利用假設市場評估法，調查讀者對於電子資源的願付價格以計算其投資報酬率；其二，參考MLA 圖書館服務價值計算方式，以館際合作之文獻傳遞價格計算讀者使用電子資源的收益以求得投資報酬率；第三是參考伊利諾大學所提出的計算方法，以研究者使用圖書館電子資源撰寫研究計畫而獲得校外研究補助案的實質效益。研究結果發現，上述3種評估方法的結果均顯示，南台科技大學圖書館在電子資源的投入成本可獲得正面的經濟效益。

Searching databases and subscriptions available online has proven to be the most expedient means for library users to acquire information needed. The library arguably bears such a mission to make available as much information online as possible. However, the cost for a library to upgrade and expand their e-services seems to be rather high, amidst school’s limited budget. Relevant ROI studies would apparently be needed to help validate the spending on a library’s online digital services. This research conducts the following three ROI assessments to investigate the case relating to Southern Taiwan University Library. First, using a contingent valuation method, a survey done to determine the ROI based on the fees users are willing to pay for e-services. Second, in reference to the service value calculator the Massachusetts Library Association uses, ROI is done based on inter-library loans and usage. Third, using the model of University of Illinois’s study in which e-resources has been proven effective for proposals to secure outside funding, ROI case in point is positive. The conclusion shows the positive economic value for Southern Taiwan University Library to invest on e-resources.