Bitcoin rose 42.7% in the third quarter of 2026, with U.S. spot Bitcoin ETFs emerging as the market's dominant demand source, according to 21shares' Q3 report. ETFs added a net 79,800 BTC worth approximately $6.2 billion during the period — nearly double the 41,300 BTC of new mining supply — displacing Bitcoin treasury companies that had previously led accumulation. Purchases by treasury firms fell sharply from $7.1 billion in Q2 to roughly $1 billion in Q3. Long-term holders sold 248,000 BTC worth about $17.4 billion in Q3, nearly three times the ETFs' net inflows. On the miner side, September revenue exceeded estimated total mining costs by 6%, ending a 10-month stretch below break-even. However, transaction fees covered only 0.67% of the network's $2.96 billion quarterly security cost, and post-2028 halving block reward revenue is projected to cover just 80% of miners' electricity expenses at current prices and hashrate levels.