The US federal government’s central energy information agency is planning to implement a mandatory nationwide survey of data centers focused on their energy use, according to a letter seen by WIRED. This survey would be the first effort of its type to collect basic information about data centers.

The letter was sent to senators Elizabeth Warren and Josh Hawley on April 9 by the head of the Energy Information Administration, Tristan Abbey, and comes in response to a previous inquiry from the senators about the EIA’s plans to get more information about data centers. WIRED reported on Hawley and Warren’s letter last month.

"Americans deserve to know how much energy data centers are sucking up and what that's doing to their utility bills,” Warren told WIRED in a statement. “The EIA's mandatory survey is an important first step towards holding data centers accountable, but people are hurting right now. I'm pushing EIA to collect and share this data as soon as possible."

The EIA told WIRED that it doesn’t have any specifics to share beyond what is in the letter to the senators.

The explosion of data centers across the US has caused an outpouring of public concern and proposed legislation to rein in their resource use, as well as put moratoriums on their construction. But there’s surprisingly little official data collected on the industry.

Most details about data centers’ energy use—a particular worry for many voters in the face of mounting utility bills—are considered proprietary business information and usually not made public. In response to encouragement from the Trump administration to protect ratepayers, many data center developers are now turning to building their own power sources, known as behind-the-meter power. These facilities—many of which are gas-powered—introduce new concerns around air pollution and climate change. (On Tuesday, the NAACP filed a lawsuit against xAI alleging it was running behind-the-meter gas turbines on a data center in Mississippi without a permit and polluting the community around it. xAI did not immediately reply to a request for comment.)

The EIA conducts mandatory surveys of providers of various types of energy generation, including oil and gas production, electric generation, and renewables, as well as their industrial customers. In late March, a day before the senators sent their letter, the EIA announced that it would conduct a pilot survey in three areas of the country that have heavy data center development: Texas, Washington state, and the northern Virginia/DC metro area.

In the April 9 letter, Abbey says that the agency will announce a second tranche of pilot surveys “covering at least three more states.” Both surveys would be complete by late September. These two pilot studies, Abbey writes, are “a necessary step in the methodical development of a nationwide mandatory survey.”

Information being collected by the EIA from data centers in these pilots, according to the letter, includes not just information on annual electricity use, but also information on behind-the-meter power generation. The surveys, Abbey writes, will also include questions on the classification of different types of data centers; cooling systems; facility characteristics, like square footage; and IT specifications, including metrics on how efficiently a data center uses energy.

The letter still leaves a lot of questions unanswered about the structure of the pilots.

According to the letter, the pilot won’t ask every respondent for the full set of metrics, but will rather tailor questions “to the particular location of each data center facility.” The current pilot also asks the 196 companies identified across the three regions to choose just one location to report metrics on. The EIA did not answer questions about how it determined which locations should receive which questions, or if it provided any requirements to survey respondents about how to go about choosing which data center location to provide information about.

The EIA also did not answer questions from WIRED about when it plans to launch the second set of pilot surveys, the states that will be included, or the possible timing of a national mandatory survey.