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After droughts and in light of future concerns over water resources, the topic of conservation has risen in importance. While regional differences in supply concerns exist across the United States and even on a smaller scale, within states, there have been consistent pushes on a federal-level to move towards more efficient use without customer behavior change. Most research suggests that behavior change is “hard,” but by addressing use at the fixture, consumers can continue flushing and showering just as much and use less water.

In addition to this push towards more efficient appliances, the rise in the water and wastewater rates across the US and more specifically, in North Carolina, have put additional incentive on users to conserve, as they are continually sent a strong pricing signal. Weather and household size can also have profound impacts on water use, but the regionality of weather and general trend towards population growth across the country make it harder to assess the impact on total use. Despite all of the factors that impact total demand, federal and state leaders remain interested in how demand is changing over time and what that means for communities strapped for supply and communities struggling to bring in sufficient revenues to cover rising expenses. 

In North Carolina, the state captures usage and metered connections data on the utility level on an annual basis, but not all utilities respond annually, or even regularly. Some utilities do respond annually, but given capacity issues for smaller utilities and overall low impact from small utilities on total state supply, none of the years capture data across the entire state. The data, known as the Local Water Supply Plan (LWSP), has been gathered since 1997, and includes metered usage and metered connections broken out by customer class, including residential, commercial, institutional, and industrial classifications. 

For a meeting of the Environmental Management Committee, the EFC had the opportunity to present results from a data analysis looking at trends in metered water use and metered connections across the state from 2002-2017, using LWSP data provided by the North Carolina Division of Water Resources. The analysis included a cohort of 119 utilities with data present in 2002, 2007, 2012, 2016, and 2017. This analysis mirrored a similar analysis conducted by the EFC in 2014 that address two questions, 1. How has residential demand changed across North Carolina?; and 2. How does that change in residential demand compare to the change in residential connections? The more recent analysis looked at a number of different trends in usage and connections, and the graphs below illustrate some of those results. 

Trends in Non-Residential Connections

Most of the analysis focused on changes in residential metered connections and use across the state, but the EFC conducted a brief analysis looking at how non-residential (institutional, industrial, commercial) usage and connections has changed. The graph that follows illustrates the results of this analysis. 

The graph can be a bit confusing, but in short, we see a general upward trend in metered non-residential connections, and a somewhat steady hold in usage. To illustrate how the non-residential usage for utilities in the cohort compared to the residential usage, we also created a graph that showed how the relative totals compared. The usage is split out by customer class (residential vs. non-residential) for all of the years included in the analysis. The results can be seen in the graph that follows. 

As illustrated in the graph, most of the usage for the cohort is associated with residential customers. This confirmed what the EFC had speculated: residential demand represents most of the demand in the state. As such, the remainder of the analysis focused on residential connections and usage.

Trends in residential use and connections

The first part of the analysis was to look at how total residential metered use and total connections have changed across the 2002-2017 period. The EFC wanted to know how the total residential metered connections have changed relative to the total residential metered usage. So, these two values were summed for each year and put on a dual axis graph, adding a linear trendline for usage. The results of that analysis can be seen below. 

The results above tell a compelling story for the state. In general, we’re seeing the number of total residential connections rising across the state. That makes sense. North Carolina is growing pretty rapidly, and that’s reflected in this result. What’s interesting is the fact that this growth in metered connections is met with a decline in total metered use. Even with some volatility in the usage over the period examined, the trend remains net decline. The same customers aren’t just using less, the fact of the matter is that there are more water customers in the state in 2017 relative to 2002, and the state is using less water. 

So that spurred the question: How much less is the median connection in the state using? Is there any difference based on utility size? The results of this question can be seen in the tables below.

What we see is that usage is declining across all groups, and some are declining quite quickly. Even after splitting up the cohort into larger and smaller utilities, we still see declines in use per metered connection. Although the median for larger utilities seemed to start with a higher per connection use than smaller utilities, both experienced similar declines. 

This pattern based on system size is particularly interesting, because it brings up the two main perspectives associated with water use changes across the state. For larger utilities, the decline in usage might be considered a success; particularly when supply constraints are met with rapid growth, or to buffer during times of drought. For small utilities though, the conversation can be much different. With infrastructure need on the rise and economies of scale at play, declining usage can have serious implications on bringing in necessary revenues. Without robust base charges, utilities are selling less of a commodity and must take this into consideration when setting rates. 

Usage changes are certainly not uniform across the state, nor are all utilities experiencing a total decline in usage. Conversely, the rise in total metered connections does follow a general geographic trend that is consistent with major growth areas in the state. In short, declines in residential usage per connection is not all sunshine and rainbows, nor is it all doom and gloom. It is very case specific and can have very different implications depending on the priorities of each community.

Austin Thompson joined the EFC at UNC in 2018 as a project director. In this role, she conducts applied research and provides technical assistance and training for environmental service providers. Thompson holds a BS in Biological Sciences from the University of South Carolina and a Master’s of Environmental Management from Duke University, with a concentration in Environmental Economics and Policy.