What is Joules per Terahash? definition, context and sources

01What is Joules per Terahash?

Joules per Terahash, written J/TH, states the joules used per 10^12 hash computations. Lower numbers mean lower energy intensity at the same measurement boundary; the unit alone does not specify a machine’s hashrate.

TH counts computations; TH/s measures their rate.
W divided by TH/s gives J/TH.
For kWh, include hashrate and operating time.
Reciprocal units reverse what a higher number means.

02A terahash counts attempts, not seconds

The prefix tera means 10^12. TH therefore counts hash computations, whereas TH/s describes their rate. The same J/TH value can belong to a small or a large machine. [NIST — SI units and prefixes]

03Seconds cancel in the ratio

W = J/s and W/(TH/s) = J/TH. Thus an illustrative 2000 W at 100 TH/s gives 20 J/TH. Two slashes without parentheses can be ambiguous; do not divide watts by terahashes and then divide by seconds again. [NIST — SI units and prefixes]

04Picojoules per hash have the same numerical value

Because pico means 10^-12, 1 J/TH = 1 pJ/hash. Thus 20 J/TH and 20 pJ/hash describe the same energy intensity, not a thousandfold difference. [NIST — SI units and prefixes]

05The reciprocal reverses comparison direction

Inverting 20 J/TH gives 0.05 TH/J, also 0.05 TH/s per W. Lower J/TH is more energy efficient; higher TH/J is better. Check which ratio a chart uses before comparing it. [NIST — SI units and prefixes]

06Daily energy needs both hashrate and time

An illustrative 20 J/TH at 100 TH/s means 2000 W, or 2 kW. Constant operation for 24 hours uses 48 kWh. With no other consumption, 12 operating hours use 24 kWh; J/TH remains unchanged. [NIST — Energy conversion factors]

07Compare changing operation over matching periods

For an actual period, divide total energy in joules by total computations in TH. Energy and computations must cover the same time; a simple average of instantaneous J/TH can distort results when hashrate changes. [NIST — Energy conversion factors]

08The unit does not define the measurement point

The 2024 S21 Pro specification lists 15 J/TH at the electrical input at 25 °C. Chip estimates or whole-site measurements have different boundaries. Braiins recommends checking power with real measurement; the same symbol does not guarantee comparable conditions. [BITMAIN — S21 Pro specification (2024)] [Braiins Academy — DPS and autotuning FAQ]

09Energy per computation does not determine the reward

J/TH does not state how many BTC you earn or the cost of mining one block. Difficulty, subsidy and fees change expected revenue per hashrate, with exchange rates also affecting dollar conversion. Do not mistake an energy unit for Hashprice or profit. [Luxor — Hashprice methodology]

↗Read in context

For the clearest picture, read this entry together with ASIC Efficiency, Hashrate, Hashprice, ASIC Miner. The reverse links also lead from ASIC Efficiency.