Elon Musk has said that Tesla will resume allowing bitcoin transactions when miners use more renewable energy. “When there’s confirmation of reasonable (~50%) clean energy usage by miners with positive future trend, Tesla will resume allowing bitcoin transactions,” Musk, the company’s CEO, said in a tweet on Sunday. Bitcoin rose 5.1% to $37,360.63 at 1810 GMT (2:10pm ET) on Sunday, adding $1,817.87 to its previous close, after Musk’s tweet. Musk also said that Tesla sold about 10% of holdings to confirm bitcoin could be liquidated easily without moving market. He announced in May that Tesla would no longer accept bitcoin for car purchases, citing long-brewing environmental concerns for a swift reversal in the company’s position on the cryptocurrency. In February, Tesla revealed it had bought $1.5bn of bitcoin and would accept it as a form of payment for cars. But the cryptocurrency’s production is at odds with the company’s mission toward a “zero-emission future”. Bitcoin fell more than 10% after Musk’s tweet in May. The billionaire said that he believed cryptocurrency has a promising future, but it cannot be at great cost to the environment. The energy used to produce bitcoin alone is equivalent to the annual carbon footprint of Argentina, according to Cambridge Bitcoin Electricity Consumption Index, a tool from researchers at Cambridge University that measures the currency’s energy use. Bitcoin mining – the process in which a bitcoin is awarded to a computer that solves a complex series of algorithms – is a deeply energy-intensive process. Because there is a finite number of bitcoins that can be mined – 21m – computers have to solve harder and harder algorithms in order to get bitcoin. The special equipment and intense processing power use a lot of electricity – as much as some entire countries. Reuters contributed to this report