MEMORANDUM
TO:
FROM:
THE COMMISSION FOR ENERGY REGULATION
IRISH WATER
DATE:
29TH MAY 2014
Key Findings - Water Consumption Research Project
SUBJECT:
1. Key Survey Findings on Consumption






Top 1% of households consume 22% of ALL water:
 Very high users of water (outliers) are influencing results; and
 Average consumption is likely to decline as leaks are fixed;
79% of households consume less than 150 litres of water per person per day;
3% of households consume less than the household free allowance of 30,000 litres per year;
Average consumption, assessed on a per person per day basis, is lower than that assumed in
recent Government announcements which assumes 145 litres per person per day 1.
 Average usage when outliers 2 are excluded is 1093 litres per person per day (when
weighted against the survey data set);
- When the survey is weighted against 2011 CSO census data set, the outlier
excluded average usage increases slightly to 111 litres per person per day.
 Average usage when outliers are included is 120 litres per person per day (i.e. across the
full surveyed customer data set).
Average consumption is equivalent to approximately 109 m3 per household per year, or
approximately 41 m3 per person per year.
Average consumption, adjusted for occupancy, is within 4% of metered properties in a similar UK
study, however it is lower (34%) than unmetered properties in the same study.
2. Background
Irish Water has carried out a survey of its metered population to capture data on averages, ranges and
variability of consumption by house occupancy, architecture type and number of bedrooms using meter
read data taken from a representative sample of customers. The broad parameters of the survey were as
follows:



1
Field Management Ireland carried out a door to door survey on behalf of Irish Water;
1,650 customers responded to survey questions on architecture type, occupancy and no of
bedrooms;
A wide geographical area and diverse range of architecture types were captured within the
survey; and
‘The average water usage per person in Ireland is estimated at 145 litres per day’ (See Q33) DECLG FAQ's on Government Free
Allowance and Water Charges
2
Outliers relate to consumption data that is deemed to be further away from the sample mean than is deemed reasonable and
suggests that such properties may have a water leak
3
A practical approach whi ch removes households using more than 800 litres per day, the assumed threshold for the first fix policy .
Households with 6+ occupants in the range 800 to 1,000 litres per day have been included as they may consume greater then 800
litres per day

3 months consumption data were captured for each customer. Consumption per day was
calculated as total metered quantity divided by number of days (we captured consumption data
for 7,5884 WPRNs of which we received 1,650 survey responses)
The aim of the survey is to help inform demand assumptions to aid the development of assessed tariffs
for non-metered domestic customers which will be included in the Water Charges Plan submitted to the
CER in June. The survey data will be used to provide confidence that the distribution of assessed
customers’ water consumption between low, medium and high is meaningful relative to metered
customers, and to support the development of the assessed tariffs, in particular the banding methodology
and number of consumption points. By assessing customers on the basis of metered consumption
patterns among comparable customers, we consider that the assessed tariff will represent as accurate a
proxy of actual usage as possible.
We have included a presentation setting out detailed analysis of the survey. The key findings are
summarised below. Phase 2 of the project to capture consumption data for children is currently being
undertaken as a response to the Government’s recent Policy Direction to the CER5. Irish Water will
submit our findings once finalised.
3. Consumption for inclusion in IW’s Tariff Model
Irish Water proposes to exclude outliers 6 when assessing consumption for inclusion in our tariff model for
the following reasons:
-
-
-
High values for consumption represent potential leaks. We have omitted 4% outliers from
WPRNs surveyed to date (4%-5% is often quoted as representing premises with leaks
nationwide);
It is a reasonable expectation that the outliers omitted from our sample will see their
consumption reduced as part of the first fix policy. We are justified in excluding such
consumption outliers when setting volumetric charges applicable until December 2016; and
We propose using the CSO adjusted overall average usage figure of 111 litres per person per
day.
The below sets out the full range of consumption Irish Water proposes incorporating in its tariff model
Figure 1 – Proposed Usage per occupancy for inclusion in Irish Water’s tariff model
4
Occupancy Band
Sample Size
1 occupant
2 occupants
3 occupants
4 occupants
5 occupants
6+ occupants
Total
94
335
353
428
265
111
1,5867
Litres/household
Per day
Per Year
171
62,415
280
102,200
324
118,260
376
137,240
414
151,110
506
184,690
298
108,756
Litres/person
Per day Per Year
171
62,415
140
51,100
108
39,420
94
34,310
83
30,295
84
30,660
111
40,658
The 120 litres (outliers included) average per person per day usage figure is corroborated when CSO average occupancy is
applied to the full 7588 consumption data set
5
Child consumption estimated as 38,000 litres per annum. To be verified through actual consumption data from metering
6
Outliers removed on the basis of the first fix policy proposed ceiling of 800 litres per property per day .
7
64 outliers excluded from full data set of 1,650 (c. 4%)