Efficiency matters more than headline hashrate, because electricity is the recurring cost while hashrate only buys a share of a moving target. A machine at 17 J/TH and one at 30 J/TH doing identical work differ by roughly forty percent on the power bill, every day.
It is the single most useful number for comparing machines across generations, and the one that determines whether hardware is still viable after the next difficulty rise or halving.
This definition is educational and not financial advice. Crypto is volatile and high-risk — always do your own research.
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