large sample size.
This paper presents a methodmanagement for estimating the method for refereed estimating the paper demand indoor and outdoor water use of residential water use of residential properties using econometric models. ometric models. Indoor and nctions were constructed Household demand is defined as a function of the ations from metered data. number of people in the dwelling (household size) applied to track indoor and and lot size (square metres) as the proxy of ng drought restrictions. It garden size. This function is fitted using quarterly have chosen to use Tracking water savings using customer metered data, the propertymetered lot size and household ter indoors even though data outdoor and econometric models size data collected through Sydney Water’s nly targeted use. demand management programs. as also applied to estimate YC Wang ney Water’s Such data collection exercises are often Before constructing the indoor AbstractWaterFix and expensive and impractical for a reasonably and outdoor demand functions, it ebate programs. OBSERVATIONS FROM CONSUMPTION DATA This paper presents Savings a method for large sample size. is worth noting how water use in a the indoor and outdoor pproach estimating are consistent with residential house varies with lot size This paper presents a method for water use of residential properties using and household size and over time. the participant and control estimating the indoor and outdoor econometric models. Indoor and outdoor It is well known that the water use of a residential water use of residential properties demand functions were constructed Figure 1 shows the monthly d. house comprises indoor and outdoor components. using econometric models. based on the observations from metered consumption of all residential houses data. The method has been applied (about 1 million) plotted with five lot The water usesize bands. depends mainly on Householdindoor demand is defi ned as to track indoor and outdoor savings The overall reduction in a function of the number of people in during drought restrictions. It shows that household size and efficiency devices demand overof timewater is mainly due to the dwelling (household size) and lot people have chosen to use significantly drought restrictions introduced from size (square metres) as the proxy of within a house. The outdoor water use depends less water indoors even though drought November 2002 (Voluntary restrictions garden size. This function is fitted using restrictions only targeted outdoor use. from November 2002; Mandatory Level on garden size, type, ownership of a quarterly metered data, the propertyplant lot se ‘endTheuse’ modelling to same method was also applied to 1 restrictions from October 2003; Level 2 size and household size data collected swimming pool and/or rainwater tanks. savings from Sydney for waterestimate andtheestimate the Water’s through from June 2004; Level 3 from June 2005; Sydney Water’s demand WaterFix and washing machine rebate replaced by Water Wise Rules from July management programs. efficiencyprograms. (WE)Savings programs estimated on using 2009); water use efficiency improvement A key challenge in modelling indoor andand outdoor approach are consistent with (for example, showerheads washing model, thisindoor residential Observations from those identified using the participant machines) and potable water substitution water useData is that there is no separate metering of Consumption om individual end uses such and control group matching method. (for example, rainwater tanks); and It the is well known the waterdemands. use of a two that water A single behaviour change. meter serves shing, clothes washing etc. Introduction residential house comprises indoor and mostcomponents. residential properties whileprofound a common meter Another feature revealed outdoor Indoor water use h indoorMany endwater use isuseusually utilities “end use” from this diagram is that the demand depends mainly on household size and serves most blocks of units. to forecast thewater demand for y data. modelling For example increases with the increase of the lot the efficiency of water devices within a water and estimate the likely impact of size during both drought restrictions house. Outdoor water use depends on s a function the water effiof ciency (WE) type programsof on water periods. garden size, plant type, ownership of a use. In this model, indoor residential Before constructing theand pre-restrictions indoor and outdoor ber of showers per person swimming pool and/or rainwater tanks. consumption is built from individual end Sydney Water has implemented one demand functions, it is worth noting how water average uses duration of toilet each such as showering, flushing, of the most comprehensive demand A key challenge in modelling indoor clothes washing etc. The water use of in the world and and outdoor use is that there is use in water a residential housemanagement varies programs with lot size consumption is usually each indoor end use is usually estimated (SWC 2010a). Since 2001, over half no separate metering of the two water household size and over time. survey data. For example, water a million residential dwellings have demands. A single meter serves most over, i.e.using the total metered use from showering is a function of residential properties, while a common participated in at least one demand mated indoor the typeuse. of showerhead, the number meter serves most blocks of units. management program. For the residential
SEPARATING INDOOR AND OUTDOOR WATER CONSUMPTION
Consumption (L/hh/d)
<=200 m2 201-400 m2 401-600 m2 601-800 m2 >800 m2
1,000
800
600
Ju
n01 D ec -0 1 Ju n02 D ec -0 2 Ju n03 D ec -0 3 Ju n04 D ec -0 4 Ju n05 D ec -0 5 Ju n06 D ec -0 6
400 ec -0 0
is very well constructed r, it is very data intensive. applied models are usually The end use model is very well constructed conceptually. However, data poor”. In order to it is very data intensive. As a consequence, the it is normally required to applied models are usually “assumption rich and data poor”. In order to calibrate ses or meter at a very short the model, it is normally required to meter an 1 minute) together individual end uses or meterwith at a very short time their interval (less than 1 minute), together diary of water use. with customers keeping a diary of their es have water been carried out in have use. Several end use studies been carried out in Australia (Loh and ghlan, 2003; Roberts, 2005; Coghlan, 2003; Roberts, 2006; Willis et al., 2009); and overseas (Mayer and and DeOreo, and overseas (Mayer 1999; Mayer et al., 2004; Heinrich, 2007). er et al., 2004; Heinrich, ection exercises are often
1,200
D
of showers per person per year and the average duration of each shower. Outdoor consumption is usually calculated as the leftover – i.e. the total metered consumption less estimated indoor use.
Figure 1: Variation of consumption with lot size.
Figure 1: Variation of consumption with lot size water
MAY 2011 63