AWWA SOURCES55580

Benefit-Cost analysis has been used for 25 years to evaluate and prioritize potential demand management measures. Oftentimes the limiting factor in such analysis, and one that some use to question the value of such analysis, is the water savings assumptions. With the advent of recent and better data on how customers use water, such as provided by the AWWARF Residential End Use Study, the water savings estimates can be made at the end use level. This increased level of complexity is justified by more reliable results. The task of computing estimated water savings and doing benefit-cost analysis is facilitated by the use of an end use model. This paper describes such a model and gives results of using the model on fourteen projects over a two-year period. The model, called the Least Cost Planning Decision Making System, or DSS has the following components: a breakdown of current water use by customer class and then by end use; parameters to forecast growth in water demand; fixture models to aid in calibrating the model to current water use conditions; a careful evaluation of the benefits in terms of O&M cost savings and the present value of capital deferrals and/or downsizing; worksheets for different types of conservation programs including fixture rebates, audits and other promotional programs, unaccounted for water reduction and pricing programs; and, a way to combine individual measures into programs with multiple measures so as to avoid double counting water savings. The output of the model includes the following features: a baseline water demand forecast with no additional conservation beyond the current codes and standards already in place; water savings, benefits, costs, and costs per unit water saved for individual conservation measures evaluated; the present value of benefits, costs and benefit-cost ratios for different combination of measures called alternative programs; and, new demand forecasts with alternative conservation programs in place. The model has been used for a number of projects over the past two years. The number of measures for each study evaluated ranged from 15 to 30. In each case some measures were cost-effective while others were not. Recommended programs saved from a few percent, on top of the existing programs already in place, to upwards of ten percent. As the DSS was first developed and first applied in Australia, some of the experiences are from there, where water use patterns are quite different from the US. The amount of effort involved in this more detailed approach are quantified. The benefits of using this approach are shown to out-weigh the additional effort involved. The calibration process provides additional insight into how customers use water and verifies that the demographic and water use data are consistent and appropriate for the service area. The additional accuracy on water savings and benefits and the ability to evaluate a large number of measures and alternative programs relatively quickly enhances the water planner's ability to be creative on program design. Includes 4 references, tables, figures.

Product Details

Edition:

Vol. - No.

Published:

01/01/2002

Number of Pages:

16

File Size:

1 file , 240 KB