A Bitcoin forum post dated Sept. 7, 2010, shows early miner TTBit estimating that a 140-watt computer producing 2,200 kilohashes per second would consume about 47.3 kilowatt-hours, or $5.68 at 12 cents per kilowatt-hour, during an average 338.05-hour wait for a block. The calculation was based on expected solo-mining time, not a guaranteed 50 BTC payout: the miner could have found a block sooner, later or not at all before difficulty changed. Bitcoin's block subsidy was 50 BTC at the time, but limited liquidity and prices generally below $1 made TTBit describe the projected electricity expense as a net loss. The discussion also documented the shift toward GPU mining, with an Nvidia GTX 260 reported at about 33,000 kilohashes per second and a 24-core AMD system estimated at 66,000 kilohashes per second. Bitcoin mining later moved from CPUs and GPUs to FPGAs and ASICs. The subsidy is now 3.125 BTC after the April 2024 halving, while network difficulty, power costs, hardware efficiency, fees and Bitcoin's price continue to determine mining profitability. A further halving is expected around 2028, reducing the subsidy to 1.5625 BTC.