The "good times" for crypto miners really do seem to be coming to an end.

Just last month it was reportedthat Bitcoin miners were selling off more Bitcoin than they were bringing in in order to cover their energy costs during the crypto crash, which saw the token plummet in value. With energy costs rising as well, mining companies were seeing profits dwindle from their mining endeavors.

Now, cryptocurrency miners have a new issue on their hands: U.S. Congress.

Congressional Democrats, led by Senator Elizabeth Warren of Massachusetts, are looking into crypto mining requirements that would force mining companies to report their energy usage. 

Senator Warren, along with five other Democratic members of Congress, wrote a letterto the Environmental Protection Agency and Department of Energy requesting that the two agencies work together to create rules requiring crypto mining companies to report on their energy use and emissions data.

The move comes, according to the New York Times, after an investigation into seven of the United States' largest Bitcoin mining companies. The inquiry found that these Bitcoin miners are heading towards using up "as much as 1,045 megawatts of power, or enough electricity to power all the residences in a city the size of Houston." Houston is Texas' most populous city and the fourth largest in the country with more than 2.3 million residents.

"The results of our investigation, which gathered data from just seven companies, are disturbing, with this limited data alone revealing that cryptominers are large energy users that account for a significant – and rapidly growing – amount of carbon emissions," reads the letter.

The letter points out that miners' energy use is also passing on additional costs for those who live and work in the cities where they are based. Notably, the Electric Reliability Council of Texas (ERCOT), which operates Texas' power grid has had to ask crypto minersin the state to voluntarily shut down operations when energy demands spike due to heatwaves.

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The largely-unregulated cryptocurrency mining industry uses massive amountsof energy due to the high-powered computer processing power necessary in order to validate transactions on the blockchain. In exchange for successfully guessing the random string of numbers required to put a block on the chain, miners are rewarded with Bitcoin. As time goes on, this process becomes more difficult and the Bitcoin remuneration will be cut in half. 

According to the report, one mining company, Marathon Digital Holdings plans to grow its operation from its current 33,000 mining rigs to 199,000 rigs by early 2023. Right now, the company powers its operation thanks to a Montana-based energy company that generates electricity by burning coal.

With crypto miners set to use up even more energy in the near future, it seems Senator Warren's letter is a step towards monitoring the industry and possibly passing regulations to curtail at least some of its more destructive behavior.