Winter Averaging

Water billing software and those who select it expect the effluent aspects of billing to be included in the package. The waste must be taken away and treated, and customers charged accordingly. A well-designed water billing application should include the ability to bill for effluent. This takes two forms - residential and commercial.

Clearly a proportion of what comes into the household as water is sent back out again as sewer or wastewater. But what is the appropriate proportion? For apartment dwellers, this proportion should be constant. For those who live in houses, however, there are all sorts of seasonal variants. These include filling the swimming pool (once or twice a year) and watering the garden (more in summer, less in winter).

Generally water billing handles the gardening side via what is known as "winter averaging", as the garden is usually not wintered during winter, when rainfall should be plentiful. That is, an average is taken of water consumption during the winter months, and this average is then calculated as the monthly charge for sewer for the entire year, winter or summer.

In Australia they do it somewhat differently. There each month is given a weighting according to its dryness, and the water consumption discounted by the weighting in order to derive the wastewater charge.

Either way, differential or seasonal billing for sewer discharge is an essential component of a water billing system.