单户住宅0.6英寸。（15毫米）水表约占加利福尼亚州弗里蒙特市阿拉米达县水区所有水表的90%，并产生约一半的年用水收入。与所有机械设备一样，这些仪表的精度会随着时间的推移而降低，从而导致收入损失增加。为了提高仪表的精度，需要以额外的成本更换仪表。最佳经济置换年限是指每年的平均成本（累计损失收入加上置换成本除以计量年限）最小。统计抽样用于分析这些仪表的精度随时间而下降的情况。然后计算了一段时间内的年度收入损失。考虑到经济和运营因素，该地区更换住宅电表的最佳年限为15年。包括3个参考文献、表格。

Single-family residential 0.6-in. (15-mm) meters make up about 90 percent of all meters for the Alameda County Water District in Fremont, CA, and generate about half of all annual revenues from water consumption. Like all mechanical devices, these meters degrade in accuracy over time, resulting in an increasing amount of lost revenue. To increase meter accuracy requires replacing meters at an additional cost. The optimal economic replacement age is when the average cost per year (cumulative lost revenue plus replacement cost divided by meter age) is at a minimum. Statistical sampling was used to profile the degradation of these meters' accuracy over time. The annual lost revenue over time was then calculated. When economic and operational factors were considered, the optimal age at which to replace residential meters in the district was determined to be 15 years. Includes 3 references, tables.