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1·There are two most widely used methods: Payback method and Return on Capital Employed.

广泛使用的有两种方法：付还法和使用 资本收益 法。

2·There are three main problems with the ROI/payback period method

ROI/偿还期方法有三个主要问题

3·However, this method has two shortcomings: (1) it ignores the time value of money and (2) it ignores the performance of the investments beyond the payback period.

然而，这一方法有两个缺点：(1)它忽略了货币时间价值(2)它忽略了项目回收期以后的经营业绩。

4·The rate of power saving and payback period were calculated with the analytical method of month by month.

结合工程实例，采用逐月分析法对该技术实施后的节电率、回收期进行了计算。