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Notes for Finding 1:
Sources of Residential
Water Cost

  • Statistics use the standard metrics for coefficients of correlation and determination, R and R2. These primarily reflect correlation of changes in cost relative to (1) consumption and (2) rates. Derivation of these metrics is in this linked Excel spreadsheet. Correlation coefficients (R) were computed from matrices containing data for each individual billing period.
  • Coefficients of determination (R2) were derived for two factors, consumption and rates. These account for 99.0% of total cost. The remaining 1.0% of total cost involves other factors.
  • Graphs for changes in rates are not shown: These are less informative, since almost all rate changes occur annually instead of per billing period. Rate-related effects can be recognized in the graphs by visually comparing the year-specific plotted data.
  • Year 2013 was the most demanding year of the recent drought. Timing of rain was a factor in producing high levels of drought stress to landscaping: The period from last spring rain to first fall rain was a full month longer than usual.

  • All data are from the billing records of this web site's author, representing a home in El Dorado Hills. Cost used is the total billed water cost, including line/cover charges. This is for a residential account in El Dorado Hills whose average water consumption is nearly identical with the average identified in EID's 2010-2011 Cost Of Services Study.
  • Charts and data will be updated later in December, 2016 to inclorporate data for the year's final billing period. (This draft predates the December bill.)
  • Data available in saved billing records began with the third billing period of 2011. Consequently, the graphs show bimonthly consumption and cost for only four bimonthly billing periods in 2011 and cannot show year-to-date totals for 2011. 
  • Water consumption data for the December/January 2015/2016 billing period was not available due to failure of the home's original water meter, which seized and reported zero flow after 25 years in service. Consumption for that period is reported as 1,200 cubic feet, based on the approximate median for the same period from other bills.

Return to Finding 1 page:
Finding F1