Joules per Terahash

The prefix tera means 10^12, or a trillion. A terahash, TH, therefore counts hashing calculations—roughly speaking, attempts in mining. Each attempt seeks a result that meets the requirement for a new Bitcoin block. TH/s instead tells you how many of those calculations the machine performs per second: its Hashrate. Think of the difference between distance travelled and a car’s speed. A small and a large machine can have identical J/TH even though the larger one does more work and draws more electricity in the same time. [1] [6]

Marek will usually find power draw in watts and speed in TH/s. A watt is a joule per second: W = J/s. Dividing power by calculation speed cancels the seconds: W/(TH/s) = J/TH. An illustrative 2000 W at 100 TH/s therefore gives 20 J/TH. The brackets matter: he divides by the whole rate. He does not divide watts by terahashes and then by seconds again. There is no need to memorise the formula; the point is to relate consumption to work done. [1]

Marek may also encounter pJ/hash in technical writing. The prefix pico means 10^-12, a trillionth. Moving from energy per trillion calculations to energy per individual calculation makes the energy unit smaller by the same factor. Hence 1 J/TH = 1 pJ/hash. The figures 20 J/TH and 20 pJ/hash describe the same energy intensity. This is not a dramatically more economical new machine, just another way to write the same quantity. [1]

So far we have looked at energy per unit of work. Someone else may report the inverse: work obtained per unit of energy. Taking the reciprocal of 20 J/TH gives 0.05 TH/J, also equivalent to 0.05 TH/s per W. In the first case Marek wants as little energy as possible for the same calculation; in the second, as many calculations as possible from the same energy. Lower is therefore better for J/TH, but higher for TH/J. Read the unit, not just the number, before comparing tables. [1]

Return to Marek’s bill. An illustrative 20 J/TH at 100 TH/s means 2000 W, or 2 kW. Running steadily for 24 hours, the machine consumes 48 kWh. If it runs for only 12 hours and draws nothing outside them, consumption is 24 kWh. Its J/TH is unchanged; the duration of its work changes. Kilowatt-hours measure the energy being paid for; Marek multiplies that by his electricity tariff to find its cost. Additional consumption, such as separate cooling, must be added separately. [2]

Real operation is not always as steady as the example. A machine may change modes or stop calculating briefly while still drawing power. For the whole period, divide total energy consumed in joules by the total number of calculations in TH. Both totals must cover the same time and measurement boundary. A simple average of a few instantaneous J/TH readings may not match the day’s result. If the equipment performs no calculations during the entire period, this ratio cannot be calculated: that would require division by zero. [2]

The unit does not tell us whether someone measured chips alone, a complete device or an entire facility. The historical S21 Pro specification from 2024 lists 15 J/TH at the electrical input with inlet air at 25 °C. That is a specific boundary and condition, not a promise of identical results in every situation. Braiins recommends checking power draw with actual measurement because software estimates can differ. Marek therefore needs to know what the figures include and under what conditions they were obtained. [3] [4]

Finally, Marek must separate electricity use from income. J/TH does not say how much BTC (bitcoin) he will receive or the electricity needed to find a particular block. Expected revenue per unit of hashrate depends on mining difficulty, newly issued coins in the reward and transaction fees; the exchange rate also affects the dollar value. Hashprice expresses expected gross revenue per unit of hashrate over a specified period. Comparing it with electricity costs and other expenses helps assess the operation’s economics. J/TH alone promises no profit. [5]