Cryptocurrency miners are turning their machines back on as the rallying price of bitcoin offers a vital lifeline to their cash-strapped businesses.

The value of the token has emerged from the doldrums to soar by more than a quarter this year against the dollar, incentivising the owners of huge warehouses of servers for mining to accelerate their use in the battle to secure more bitcoins.

The average hashrate, or the computing power directed towards mining bitcoin, rose to a record 280 exahash — or quintillion — operations per second on January 20, according to data from Hashrate Index, a mining information service.

The upsurge in activity is a sign that the battered sector may be crawling back to life after being buffeted by high energy costs and the slumping price of the cryptocurrency. The activity level has more than doubled from a low point in July, when the crypto market was hit by a credit crisis.

Miners race each other to solve cryptographic puzzles that validate batches of transactions and create new blocks in the blockchain, a ledger of deals. That makes them the guarantors that bitcoin deals are trustworthy in a system that bypasses third parties such as banks and exchanges. The winner is rewarded with new coins.

Many are sat on large quantities of mining equipment and capacity, bought with cheap money in 2021 and early 2022 in anticipation of turning a profit from the rising price of coins. But bitcoin prices slumped 65 per cent last year and energy…