Calculations and Math
Fixed Costs:
The 7 day average of the Bitcoin network hash rate, as of November 23rd 16:00 UTC, is 41,483,931 terahashes.
https://www.blockchain.com/en/charts/hash-rate
S9i ASIC specifications: 14 terahashes; consumes 1320 Watts; costs $307 per unit
T15 ASIC specifications: 23 terahashes; consumes 1541 Watts; $913 per unit
https://shop.bitmain.com
To acquire more than 50 percent of the Bitcoin network, an attacker would need at minimum the same number of ASICs that are already in circulation.
Network hash rate / terahashes per ASIC = number of ASICs necessary to acquire 50 percent
41,483,931 network terahashes / 14 terahashes = 2,963,138 S9is
41,483,931 network terahashes / 23 terahashes = 1,803,649 T15s
Calculations for total current ASIC usage: 2,963,138 * 1.75 (crude estimate accounting for older models) = 5,185,492
2,963,138 S9is * $307 per S9i = $909,683,366
1,803,649 T15s * $913 per T15 = $1,646,731,537
Including bulk discount of 10 percent for the size of the purchase and economies of scale.
Total for S9is after discount = $818,715,029
Total for T15s after discount = $1,482,058,383
Infrastructure costs such as housing are a multiple of hardware costs from anywhere between an additional 22 percent to 40 percent, according to the CEO of a large-scale mining operation based in Canada. We will use the low figure to again account for economies of scale.
S9i infrastructure costs: $818,715,029 * 22% = $180,117,307
T15 infrastructure costs: $1,482,058,383 * 22% = $326,052,844
Variable Costs:
Costs of daily electricity consumption for S9i:
2,963,138 ASICs * 1320W = 3,911,342,160 Watts
3,911,342,160 Watts / 1000 = 3,911,342 kWh
3,911,342 kWh * 24 hours = 93,872,212 kWh per day
93,872,212 * $0.03 per kWh = $2,816,166 per day in electricity
Electricity costs based the low-end of the electricity rates in Washington State, the state with the average lowest electricity costs in the United States:
https://www.electricitylocal.com/states/washington/
Costs of daily electricity consumption for T15:
1,803,649 T15s * 1541 Watts = 2,779,423,109 Watts
2,779,423,109 Watts / 1000 = 2,779,423 kW
2,779,424 kW * 24 hours = 66,706,155 kWh
66,706,155 kWh * $0.03 per kWh = $2,001,185 per day in electricity
Cost of labor and maintenance above electric costs: 10%. This is an estimate based on an interview with two different large-scale miners in Canada and Georgia who chose to remain anonymous.
Average kWh: ((((3,911,342,160 Watts + 2,779,423,109 Watts) / 2) * 24 hours) * 365 days) / 1E12 watt hrs per terawatt hrs = 29.3 TWh
This estimate is short of Denmark’s oft-cited annual energy consumption of 32 TWh, closer to Morocco's consumption of 29 TWh.
S9i: ($2,816,166) * 10% = $281,616
T15: ($2,001,185) * 10% = $200,189
Total Costs:
S9i fixed costs: $818,715,029 ASICs + $153,099,711 other infrastructure = $971,814,740
T15 fixed costs: $1,482,058,383 ASICs + $326,052,844 other infrastructure = $1,808,111,227
S9i daily variable costs: $2,816,166 electricity + $281,616 misc. = $3,097,782
T15 daily variable costs: $2,001,185 electricity + $200,189 misc. = $2,201,374
51% attack may require at least 10 days of sustained mining, at a minimum, based on the recent Bitcoin Cash hash wars:
S9i 10 days of mining: $3,097,782 * 10 days = $30,977,820
T15 10 days of mining: $2,201,374 * 10 days = $22,013,740
Total cost of S9i attack: $971,814,740 + $30,977,820 = $1,002,792,560
Total cost of T15 attack: $1,808,111,227 + $22,013,740 = $1,830,124,967
Average cost of an attack: ($1,002,792,560 + $1,830,124,967) / 2 = $1,416,458,764
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