In a letter sent to the Electric Reliability Council of Texas, aka ERCOT, Sen. Elizabeth Warren and her fellow congressional Democrats ask how the Texas electrical grid is subsidizing crypto mining groups when they subsidize their companies during peak demand.

During the summer, when Texas temperatures rose over 100 degrees, ERCOT asked major companies, including bitcoin mining operations, to shut down operations when electricity use spiked. The Texas Blockchain Council, an association representing the dozens of crypto mining companies in the state, had previously said that the companies had acquiesced to ERCOT’s request and freed up close to 1% of Texas’ grid.

Warren’s letter also cites that Texas is already home to a quarter of all bitcoin mining and 9% of all the mining power across the globe. That number may grow to around 20% by the end of 2023, according to industry insiders cited by Texas Monthly in August. At the same time, the energy used to mine bitcoin and ethereum, the two largest cryptocurrencies by market cap, resulted in 80 million tons of carbon dioxide emissions back in 2021.

Despite this open-handed gesture to the people of Texas, there was also an economic incentive at play. Of course, peak energy use also promotes a higher price per wattage, so miners were incentivized to cut down on use. Warren’s letter cited Gizmodo’s past reporting about how one of Texas’ biggest crypto mining operations headed by Riot Blockchain actually made a profit when it voluntarily went offline during the hottest summer months thanks to a power purchase agreement with ERCOT. More than that, the White House’s recent crypto and climate report noted:

“Increased electricity demands from crypto-asset mining also increase the overall peak level of grid demand. While reducing this peak during a grid emergency is valuable, the increased peak is often why demand response is necessary, establishing misaligned incentives between crypto-asset miners and grid operators.”

Warren and her fellow Democrats asked ERCOT about the annual electricity consumption by cryptominers in the past five years and the calculated carbon dioxide emissions from that energy use, the nature of the company’s power purchase agreements, and how crypto mining companies plan to grow in Texas.

According to a July letter sent to the EPA from Warren and other congressional representatives, the biggest Texas mining operations were drawing approximately 1,045 megawatts of electricity, a number they estimated could power all the residential homes in Houston, Texas. Though these numbers were based in February, before the May crypto crash sent the entire industry into a bear market, Riot Blockchain was using a capacity of over 400 megawatts from both its Coinmint and Whinstone facilities.

In a response letter provided to Gizmodo, the TBC contested Warren’s assertions, and proclaimed that miners curtailed over 50,000 megawatt hours in July during the heat wave and are creating jobs in rural Texas communities while putting millions of dollars into state and local coffers through tax payments. The council also argued that the demand-response power programs they participate in are available to any industrial or commercial power consumer, not just crypto miners.

But even without Warren and co.’s letter, Texas crypto mining could be on the outs. According to a report from CoinDesk at the end of August, the Texas Blockchain Council director of bitcoin mining analytics, Steve Kinard, said ERCOT was already dialing back how many new mining permits it was issuing. More than that, Kinard said there were fewer places that new mining operations could simply plug into without building up expensive supporting infrastructure first. Despite the permit slowdown, Kinard said grid operators didn’t say outright that they were no longer interested in attracting new mining operations.

What may be knocking miners even more is the second most-popular cryptocurrency ethereum transitioning from proof-of-work to proof-of-stake, which promised to cut out the need for most mining operations, effectively reducing the power demand by 99%, at least by some estimates.

The lone Texas representative who signed the letter was Al Green, whose district is in Houston. Green did not immediately respond to a request for comment Wednesday evening.

Update Oct. 13 at 12:20 p.m. Et: This post was updated to include a response from the Texas Blockchain Council to Warren’s letter.