Water Savings in Eddy Home Households. Dr. Tricia Barfoot, July 2017

Transcription

1 Water Savings in Eddy Home Households Dr. Tricia Barfoot, July 2017

2 Motivation We estimate total water savings by comparing the actual water use by Eddy Home households to their expected water use based on the customer s specific geographical and household information. We estimate water savings due to leaks based on an in-depth study of leak alerts generated by the Eddy solution. Summary of Findings On average, Eddy households use 14% less water than expected but the savings is larger than this for a majority of households. 1 out of 2 Eddy households uses at least 26% less water than expected. On average, each household loses more than 10.8 L/hour due to leaks each day. The most common type of leak is a toilet leak using 2 L/min on average. Based on a reasonable assumption of the reduction in time to detect a leak through the Eddy solution, then Eddy households save approximately 23 L in water loss due to leaks per person each day.

3 1. Total Water Use We base expected water use on the most significant residential study of water end use in North America to date1, conducted in 2016 by Water Research Foundation, known as Residential End Uses of Water, Version 2 (REU2016). One objective of REU2016 is to develop predictive models to assess and forecast residential demand. Flow monitoring equipment was installed and high-quality flow data were successfully obtained from 762 homes spread across 9 geographical sites. A mail survey was also collected from these 762 homes which provided the customer s household information. Additionally, billed consumption data were collected from 23,379 single-family homes across 23 geographical sites. a) The flow data and household information were the basis of predictive mathematical models that relate explanatory variables to indoor and outdoor water use in single-family households (¹ Tables 7.1 and 7.12). The average observed values of each of the explanatory variables are provided (¹ Table 7.9). b) The billed consumption data were the basis of annual and non-seasonal per capita use statistics for each of the 23 geographical sites (¹ Table 6.2). 1.1 Methodology We select all Eddy Home customer households that were active during the entire months of April and May We compile their available geographical and household information. For each customer, we estimate these values of expected usage over this time period: Predictions of indoor and outdoor water use based on a) and known household information. Where the value of the explanatory variable for the particular customer is not known, we use the

4 average observed value from REU2016. Per household non-seasonal water use based on b) and known number of residents in the customer s household. Where the customer s geographical location is not one of the REU2016 study sites, we use the closest proximity study site or a population weighted average of all sites within the same state. Since April and May have some outdoor water use but are not peak outdoor water use months, we calculate the three estimates: 1. Indoor water use + 5 x outdoor water use 2. Non-seasonal water use + 5 x outdoor water use 3. 5 x estimate x estimate Data and Results The total water volume consumed by each Eddy Home household that was active from April 1 to May 31, 2017 is calculated. A small percentage of these households are removed from the analysis since their total observed water consumption over this time period is less than 200 L. There is a significant positive correlation between estimates 1, 2, and 3, as stated in Section 1.1, and the value of actual water volumes by household. By comparing the value of actual water volume and the estimate 3 of expected water use for each customer household, we have the following results.

5 16% Less water use than expected More water use than expected 10 Relative Frequency 14% 12% 8% 6% 4% 72% of Eddy customers use less water than expected 1 out of 2 Eddy customers uses at least 26% less water than expected On average, Eddy customers use 14% less water than expected Cumulativve Frequency 2% < Actual water use relative to expected > Conclusion Based on a combination of two estimates of expected water use by the most significant study of residential water use in North America1 (REU2016), we show that 72% of Eddy Home customers use less water than expected. On average, Eddy households use 14% less water than expected but the savings is larger than this for a majority of households. 2. Water Use Due to Leaks 2.1 Methodology We use results from an in-depth analysis of alert events in order to estimate the percentage of alerts that are false positive or indicators of leaks. We apply these findings to the entire set of alert events over a two-month period to estimate the flow rate (L/hour) of water due to leaks in each household each day. Based on the estimate of flow rate due to leaks, we illustrate an estimate of water savings given the fact that the ddy solution alerts the homeowner to leaks sooner than they

6 would detect the leaks if they have no Eddy Home solution. We compare the findings to other estimates of savings due to leaks. 2.2 Data and Results In the months of April and May, Eddy Home alerted their customers to an average of one inconsistent water event per customer household every 17.1 days. An inconsistent water event is identified by water use flow rate and duration that is inconsistent with the household s past usage represented by flow rate thresholds and continuous use detection times by time period. Multiple events on a single day for a single household are counted as a single event using the highest threshold value. Following is the distribution of the flow rate thresholds in L/min of the inconsistent water events. Note that in the case of a leak, the flow rate of the leak is at or above the threshold level. 35% 36% 10 9 Relative Frequency 25% 2 15% 5% 15% at 5 L / min 4% at 40 L / min Cumulativve Frequency Flow Rate [L/min] The most common thresholds are 0.1 L/min (36% of all events), 5 L/min (15% of all events), and 40 L/min (4% of all events). In total over 61 days, Eddy Home customers were alerted to inconsistent water use of more than 26K L/min or equivalently 1.57 million L/hour. This is an average of more than 16.7 L/hour for a single household each day.

7 In April and May 2017, an in-depth evaluation of select alert events was conducted to classify these events into false positives or the type of leak detected. The alert events to evaluate were selected based on the Incident Action code assigned in the Control Room and the snoozed alert reason code, where specified. Events more likely to be a leak based on these codes were selected for evaluation. In the case of a leak, the type of leak was confirmed with the customer. Among a set of 97 select events, 83 (86%) were found to be leaks and 14 (14%) were false positives. Among the identified leaks, a toilet leak is the most common type and accounts for 4 of confirmed leaks. Following is the distribution of the type of leaks among the identified leaks. 4 4 Relative Frequency 2 7% 5% 4% 2% 1% 1% Toilet Leak Faucet Leak Hose Leak Water Heater Leak Shower Leak Irrigation Leak Type of Leak Sink Leak Plumbing Pipe Leak Other Leaks In the case of these leaks, the amount of unintended water loss can be estimated based on the flow rate threshold at the time when the alert is generated. The leaks with the highest thresholds are the shower leaks with 2.9 L/min on average followed by the toilet leaks with 2.0 L/min on average. In total,

8 these 83 identified leaks exceeded thresholds of 94.9 L/min or equivalently 5.7K L/hr. Note that the actual flow rates of the leaks are likely higher than these threshold levels. We can apply the results of this evaluation to the entire set of alert events in April and May based on the same criteria for Incident Action and snooze reason as the select events discussed previously. Based on these criteria, there is, on average, one inconsistent water event alert per customer household every 23.7 days, up from 17.1 days. On average, Eddy Home customers were alerted to inconsistent water use of roughly 12.6 L/hour per single household each day. If we apply a leak percentage of 86% as found through the evaluation discussed above, then we estimate that each Eddy household loses 10.8 L/hour due to leaks each day. As an illustration, if a particular household without the Eddy solution took an extra 3 hours on average to detect a leak as compared to a household with the Eddy solution, then that household would lose an average of 33 L more water due to leaks each day on average. Under this scenario, then, we estimate the Eddy Home solution saves the average household 11.9K L of water each year. Note that the time to detect a leak without the Eddy solution could be much longer than this and actual leak flow rates are likely higher than threshold values, so larger savings are likely. 2.3 Conclusions Based on results from an in-depth study of Eddy alerts, we estimate that each household loses more than 10.8 L/hour due to leaks each day. The Eddy solution saves its customers water use due to leaks since it alerts the homeowner to the leak as soon as the period of continuous use is longer than that homeowner s usual use patterns. In the case where the Eddy solutions alerts the homeowner to the leak 3 hours before the homeowner would otherwise detect it, then we estimate the Eddy solution saves the household more than 11.9K L of water each year.

9 We compare these estimates with the estimates based on other methodology. The REU2016 study states that the water loss due to leaks can be estimated as 29.9 L per person per day. A June 2017 study entitled Eddy Home Customers Savings in Water Use, CO2e Emissions, and Municipal Energy 2 states that the Eddy solution saves 77% of water loss due to leaks through leak alerts. That amounts to a savings of 23 L per person per day or 60.8 L per household per day, given that the household has an average 2.64 persons. In comparison to the estimate of 10.8 L/hour lost per household due to leaks each day, the two are comparable when the leak is detected 60.8/10.8=5.6 hours sooner with the Eddy solution. Given that the estimate of loss due to leaks each day at 10.8 L/hour is a lower bound estimate and that detecting the leak sooner by ~5 hours seems reasonable, then we have general agreement between the two estimates of water savings due to the Eddy solution. References 1. Water Research Foundation. Residential End Uses of Water, Version 2: Tricia Barfoot. Eddy Home Customers Savings in Water Use, CO2e Emissions, and Municipal Energy, June 2017.