CPLT-Residential

Residential Consumption Volume Issue

This issue is that Aqua’s data requires at least 1,303 of New Garden’s 1,916 residential customers to consume zero water volume for Aqua’s numbers to work. That is totally unrealistic. New Garden is not a ghost town.

So why would 1,303 customers have to use zero water?

Here is my consolidation of Aqua’s residential consumption data in their 2021 rate filing:

There is some number of customers using >5,000 per billing period. We do not know what that number is, but we can make an assumption about it and test what that assumption tells us. To illustrate, assume the over 5,000 user averages 12,000 gallons/month. That means:

700 customers are needed to fill the over 5,000 rate band
[700 = 58,758,600/(12,000 – 5,000)/12].

Those 700 customers would contribute 27,980,286 gallons to the “1667 ‑ 5,000” rate band
[27,980,286 = 700 x 3333 x 12].

However, 27,980,286 gallons is far greater than the actual volume for the “1667 ‑ 5,000” rate band. Therefore, it is an impossible situation. Repeating this calculation using larger average volumes will show that this situation persists until the big user exceeds 16,000 gallons per month.

Therefore, let’s consider another example where the large user averages 21,000 per month. The following table outlines this case:

The High Volume Rate Band:

#1 - 306 customers are needed to fill the over 5,000 rate band
[306 = 58,758,600/(21,000 – 5,000)/12].

#2 - Those 306 customers would contribute 12,241,375 gallons to the “1667 ‑ 5,000” rate band
[12,241,375 = 306 x 3333 x 12].

#3 - Those 12,241,375 gallons are less than actual volume for the “1667 ‑ 5,000” rate band, so this is a possibility.

The Middle Volume Rate Band

#1 - The big 21,000 gallon users have already consumed all but 5,584,725 gallons in this rate band. The customers using between 1,667 and 5,000 gallons must consume this amount.

#2 - Assume all these customers use the full 5,000 gallons because it will minimize the number of zero users. The math results in 140 customers using the 5,000 gallon limit:

140 customers are required [140 = 5,584,725/12/3333].

#3 - Those 140 customers also contribute 2,792,363 gallons to the “0 ‑ 1667” rate band.
[2,792,363 = 140*12*1,667]

Low Volume Rate Band

#1 - The two other rate bands have already contributed 8,913,051 gallons to this rate band. But, that is fine because it is less than the total volume in the rate band.

#2 - There are 666,950 gallons remaining in this rate band for the low volume users. Here we assume each user consumes only 333 gallons. This is the minimum possible use, and it maximizes the number of active users. Those assumptions result in 167 customers using this volume.

[167 = 666,950/12/333 ].

#3 - Adding up the number of customers in each rate band you find that only 613 out of the 1,916 used any water. If any of those other 1,303 customers used any water, the total consumption allowed would be exceeded.

It is interesting to note that no matter what you assume for the >5,000 gallon customer, as long as it is greater than 16,000 gallons, it always results in 1,303 customers using zero water. Here is a table illustrating the result:

For those who want to tinker with the numbers themselves, here is the spreadsheet I used to do the above calculations. You will find two possible outcomes: an impossible negative volume or 1,303 customers using zero water. Also, if the middle band user consumes less than 5,000 gallons the number of zero users will be greater than 1,303.