A new study looking at how to measure the affordability of water for residents says Phoenix beats all other large cities in the country.

According to analysis by Manny Teodoro, associate professor at Texas A&M University, Phoenix has the most affordable water when you look at the bill for water and sewer as a part of a family’s disposable income. He also writes that compared to other cities, a Phoenix resident paying a water bill would need to work the fewest number of hours at minimum wage.

Teodoro said Phoenix keeps basic water use relatively cheap. “The basic level of service is mostly captured in [a] fixed rate,” he said. “So those rates are pretty low. And then Phoenix’s rates jump up really high for higher-volume customers.”

One caveat is that the comparison doesn’t account for any financial assistance programs utilities or cities may have to help low income residents. Another is that the analysis focuses on single-family residences and does not include renters.

In his study, Teodoro takes issue with a number often used in the U.S. to determine affordability: the median household income. Teodoro thinks it doesn’t properly account for the tradeoffs a lower-income household might make in order to pay its water bill.