October update

This update is written mainly for the people who run water utilities. If your utility appears on whatwatercosts.org, here is what changed in October and how to tell us when we've got something wrong.

Coverage

We now publish a bill for 7,011 utilities, serving about 267 million people. That includes most utilities serving more than 10,000 people and, for the first time, about 2,700 smaller systems serving 3,300 to 10,000. We also finished a pass through every community water system in California.

You can find your utility by name, city or ZIP code from the home page, or browse by state, for example California or Texas.

Some utilities still show no bill, or a bill marked as under review. Usually that's because we couldn't find a current rate schedule online, which is harder than it sounds. If yours is one of them, send us your rate schedule and we'll add it.

Accuracy

An AI agent reads each utility's official rate schedule and calculates the bill. In October we added checks on top of that:

• A second reading. When the first reading isn't clear enough to publish, the agent reads the schedule again, more carefully.
• A nightly audit. A separate AI model finds the rate schedule on its own and calculates the bill without seeing ours. Where the two agree, the bill is marked as checked. Where they disagree, we correct it or a person decides.
• Two amounts when unsure. If we can't settle on one figure, the page shows both ("$A or $B") rather than guessing.

We also checked a random sample of 30 published bills against their rate schedules: 24 were right, three were wrong and three we couldn't settle. Most errors were charges the agent missed, and we're changing how it reads schedules to catch them. Our methodology reports these results in full.

If your utility's bill is wrong, use the feedback link on its page, or contact us. Corrections usually go up within a day, and we record them openly. When rates change, sending us the new schedule is the fastest way to update your page.

Methodology

We rewrote our methodology from scratch. In brief:

• What we measure. The monthly water bill for a single-family home using 6,000 gallons, on the smallest standard meter, at inside-city rates. Water only: no sewer, stormwater or trash.
• What counts. Every recurring charge that all residential customers pay, including service charges, usage charges and mandatory fees such as water-supply surcharges. Taxes listed separately on the bill, and one-off credits, are left out.
• How a bill is made. Each utility page now shows the parts of the bill (service charge, water and fees), which household it describes, and whether rates vary by area within the utility.
• When we hold a bill back. We would rather show nothing than a figure we can't support.

The code behind each release is open source, and the data is free to use with credit: see versions, data and API and how to cite.

Thanks for following along.

-MT