X倍數(Factor X)是一種將產品的價值與產品對環境的衝擊數值化，並進一步比較新舊產品進步率的指標方法。本研究有別於以往X倍數只著重於產品規格性能的價值評估方式，提出產品價值評估應包含：製造(Production)、使用(Use)、廢棄處理(Disposal)三階段，進行產品價值評估，與生命週期評估(Life Cycle Assessment)方法相互呼應。在製造階段(Production Stage)，沿用傳統X倍數利用規格性能進行評估的方式。在使用階段(Use Stage)，導入產品價值會隨時間衰退的觀念，計算產品在使用階段之產品價值。在廢棄處理階段(Disposal Stage)，利用Reuse評估剩餘價值並進行廢棄處理階段的產品剩餘價值估算。在產品環境負載方面提出利用生命週期評估軟體可能出現的問題，挑選溫室氣體為目標建立方法架構，並進行生命週期評估軟體之資料庫蒐集。最後，整合三階段之產品價值，並與產品環境負載(Environmental load)計算得到生態效率(Eco-efficiency)，進而得到新、舊產品之產品進步率。

Factor X indicator is a way which quantifies the value of the product and the environmental impact caused by the product. It compares the improvement rate of the new product with the old one.
Differentiated from the former Factor X indicator method which focused on specifications of products, this study recommends that the evaluation of the product value should include production, use, and disposal three stages by using the same concept as life cycle assessment (LCA).
This study follows former Factor X indicator method to calculate improvement rate of products by specifications during the production stage. As for use stage, it quotes the concept which the product value deteriorated with time to calculate the value. The residual value and the reuse percentage of product are used to evaluate the product value in the disposal stage.
In product’s environmental load, this study points out some possible problems caused by using LCA software to analyze products. Regarding global warming as the major target, this study proposes the procedures of the solution, and collects data on the database of LCA software.
This study integrates all of the product values in three stages, and gets eco-efficiency by combining with the product environmental load. Finally, from Eco-efficiency, this study obtains the improvement rate between new and old products.

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