Methodology
How we measure water.
Water has no single global price. A household bill, a desalination tariff and a water right are different things. We measure them separately.
What we measureWhat one household pays for 15,000 litres of tap water in a month, and separately what it pays once wastewater is added.
Why 15,000 litresA yardstick, not a claim about an average home. It is the point at which each published tariff is measured.
What is countedThe volumetric charge, standing and meter charges, surcharges, and tax. Everything a household must pay to receive water.
What is notConnection fees, deposits, penalties, means-tested discounts, and property charges such as housing fees.
Why wastewater is separateIn New York it is 61% of the bill; in Dubai 31%. Folding it in would hide the difference.
CurrenciesLocal currency only. A converted figure needs an exchange rate fixed to a named month; until that is set we publish none.
How we checkA primary document, an archived copy stored under a hash, and a publication checklist of
7 conditions every one of which is checked by code on every build — among them that
each stored rate appears verbatim in its own archived capture. The two-person review this page
once described was withdrawn in v1.3: the system contained one reviewer, so it held fully
evidenced cities indefinitely and caught nothing. What replaced it runs every time and never forgets.
What we do not sayA utility publishes its rate; a bill also carries surcharges and taxes, published too. Our figure is larger because it answers a different question, not because anything was concealed.
The sum
cost per 1,000 litres = the month's bill ÷ 15
the month's bill = volumetric charge through the published blocks
+ standing and meter charges
+ surcharges
+ tax
− universal automatic rebates
The same sum is measured at 5, 10, 15, 20 and 25 m³, because two cities can cost the same at one volume and behave differently either side of it.
Comparability
Grade AReproducible from the current official tariff with no material assumption. May be ranked.
Grade BOne disclosed assumption, and the bill could be more than one number by up to 1%. Shown with notice.
Grade CA system that cannot be standardized, or ambiguity above 1% of the bill. Shown as context, never ranked.
A grade measures uncertainty, not scope. Where a figure describes a defined subset of households — a metered account in a partly metered city — that is printed beside the figure as a disclosure. It is not an error, and it does not lower the grade.
The index
NameTWJ Urban Water Tariff Index (UWTI) measures the structural level of
residential tariff liability for a standard household service bundle. It records what a household is liable to
pay under the published tariff, not the utility’s cost of producing water.
Earlier versions used the name Water Cost Index (WCI). It was renamed
because the measure concerns tariff liability, not production cost.
Headline numberTWJ Standardized Water Price, in local currency per m³
Basket readingThe structural price. Where a city carries explicitly temporary relief, the page leads with what a household pays today and the basket uses the standing tariff — a base period must not embed a policy that will expire while the base does not.
Version
Methodologyv1.9, frozen 2026-08-18 · supersedes v1.8, which is retained unaltered
ScenarioTWJ-R180-v1.0
Base periodTWJ-2026 · month not set. The basket month can be fixed only when every constituent is evidenced for the same month. In the current basket, Dubai is the binding constraint: DEWA sets its fuel surcharge monthly and publishes only the month in force, so the Dubai record is evidenced for August 2026 and nothing held here evidences July. The base month is set when the basket is real, not before.