A fixed cost does not change with your behavior. My bimonthly water bill from EBMUD has a "water service charge" of $19.06 and "seismic improvement program surcharge" of $3.52. I pay these charges even if I use NO water.
A variable cost changes with your behavior. EBMUD has a "water flow charge" of $2/unit (one hundred cubic feet -- ccf -- or 748 gallons) and "drought surcharge" of $2/unit for "excessive use" (see Stupid Water Bills).
So EBMUD is collecting money from me for having a connection and for the amount of water I use. That seems to be a no-brainer, but here's the twist: This billing structure probably does NOT match EBMUD's costs.
According EBMUD's Budget Fact Sheet [PDF], 73 percent of its costs (debt service + capital appropriation) are fixed and 27 percent (operating expenses) are variable. 27 percent is WAY too high, of course, since salaries are included in operating expenses. Let's just say that 80 percent of EBMUD's expenses are fixed and 20 percent are variable.
Now get back to EBMUD revenues. If we take my water bills as typical, then 47 percent of EBMUD's revenues are fixed and 53 percent are variable.
Why does this matter? If everyone reduces their water use by 20 percent, EBMUD revenue will drop by 10.6 percent but its costs will only drop by 4 percent. Given that EBMUD -- a public utility -- runs on a break-even basis, such a change in costs and revenues will result in a "revenue shortfall," and EBMUD will have to raise rates to cover the losses.
(Note that Metropolitan Water District of SoCal has revenue that's 80 percent variable and costs that are 80 percent fixed; see p15 in my dissertation. In fact, most water utilities -- both public and investor-owned -- have this "upside down" structure.)
Those of you who have noticed the "use less, pay more" pattern at utilities experiencing water "shortages" will now understand three things:
- Utilities hit shortfalls because mostly variable revenues are dropping faster than mostly fixed costs.
- The resulting rate increases are unpopular because they appear to punish conservation.
- Utilities do NOT LIKE conservation because they will have to increase rates, a process that forces water managers to appear in public and be questioned/insulted by politicians and irate ratepayers.
- The "right" way to bill customers for water is to charge a fixed price in proportion to fixed costs and variable price in proportion to variable costs.
- This is not done, IMO, because the People want water bills to reflect water use -- so "water wasters" cover most of the costs of water service.
- My own policy prescription of "some water for free, pay for more" is based on variable prices being a BIG part of people's water bill.
And that's today's lesson :)
Bottom Line: Water bills do not reflect the cost of delivering water. If people vary their behavior, financial imbalances result and things get messy. If we fixed water bills (cover fixed costs and feebate variable costs), we would see the end of "I conserved water, and now I pay more!" headlines.