What Is J/TH? Understanding Bitcoin Mining Efficiency
J/TH — joules per terahash — is the most important spec for comparing bitcoin miners. It measures how many watts a miner consumes to produce one unit of hashing work. Lower is more efficient: the Whatsminer M70S at ~13.5 J/TH is more efficient than both the M70 at ~14.5 J/TH and the hydro-cooled M73 at 14.5 J/TH.
This matters because electricity is your largest ongoing operating cost. At $0.07/kWh, a 1 J/TH difference on a 258 TH/s machine translates to roughly $20/month in electricity savings per miner.
How J/TH Is Calculated
One joule equals one watt-second. Because we measure hashrate in terahashes per second (TH/s), J/TH is simply:
J/TH = Power (watts) ÷ Hashrate (TH/s)
Example with the Whatsminer M70S running at its nominal spec:
3,500 W ÷ 258 TH/s = 13.57 J/TH
Actual efficiency may vary slightly depending on operating mode, ambient temperature, and firmware version.
Why J/TH Matters More Than Hashrate Alone
A machine with more TH/s earns more mining rewards — but only if the extra hashrate doesn't cost more in electricity than it earns. A high-hashrate miner with poor efficiency can actually be less profitable than a lower-hashrate machine with better J/TH, depending on your electricity rate.
Consider: running a 7,200W M73 at $0.07/kWh costs approximately $362/month in electricity. Running two 3,500W M70S units for approximately the same hashrate (~516 TH/s) costs about $353/month — while also using less total power and producing more TH per dollar of electricity. The M73's advantage is density (470–526 TH/s in one chassis) and silent hydro operation, not electrical efficiency.
Comparing Our Miners by J/TH
| Model | Hashrate | Efficiency | Power Draw | Cooling |
|---|---|---|---|---|
| Whatsminer M70 | 214–242 TH/s | ~14.5 J/TH | ~3,140–3,500 W | Air |
| Whatsminer M70S | 226–258 TH/s | ~13.5 J/TH ✓ most efficient | ~3,500 W | Air |
| Whatsminer M73 | 470–526 TH/s | 14.5 J/TH | ~7,200 W | Hydro |
Note on the M73: The M73's advantage is raw hashrate (470–526 TH/s) and hydro-cooled density — not energy efficiency. At 14.5 J/TH it is less efficient per terahash than both air-cooled models. Choose the M73 when you need maximum hashrate in minimum rack space and have hydro infrastructure.
What Is a Good J/TH in 2026?
The leading edge for air-cooled ASICs in 2026 falls in the 13–15 J/TH range. The absolute efficiency frontier — on the newest generation hardware not yet in wide deployment — approaches 10–12 J/TH. For the Whatsminer M70 generation:
- →13.5 J/TH (M70S) — competitive; among the better air-cooled options in this generation
- →14.5 J/TH (M70) — reasonable; viable at low electricity rates
- →14.5 J/TH (M73) — less efficient per TH than M70S; justified by density and quiet hydro operation at scale
Frequently Asked Questions
What does J/TH mean in bitcoin mining?
J/TH stands for joules per terahash. It measures how many joules of electrical energy a miner consumes to produce one terahash (10¹² hashes) of computational work. Because one joule per second equals one watt, J/TH is essentially watts per terahash per second — or how many watts your miner needs to run at its rated hashrate. Lower J/TH = more efficient.
Is a lower or higher J/TH better?
Lower is better. A miner with 13.5 J/TH consumes less electricity per terahash than one with 14.5 J/TH, all else equal. Over continuous 24/7 operation, the difference in electricity cost compounds significantly. The Whatsminer M70S at ~13.5 J/TH is more efficient than both the M70 and hydro-cooled M73 (each at ~14.5 J/TH).
Why is the Whatsminer M73 less efficient than the M70S if it's a newer hydro model?
The M73's advantage is raw hashrate (470–526 TH/s) and hydro-cooled density — not energy efficiency. At 14.5 J/TH, it actually consumes more electricity per TH than the air-cooled M70S at ~13.5 J/TH. Hydro cooling enables more hashrate in a smaller physical space and reduces operational noise, but it does not automatically make a machine more energy-efficient.
What is a good J/TH rating for a bitcoin miner in 2026?
Leading-edge air-cooled ASICs in 2026 generally fall in the 13–15 J/TH range. The Whatsminer M70S at ~13.5 J/TH is among the more efficient options in the M70 generation. The absolute frontier for efficiency in 2026 is in the 10–12 J/TH range on newer product lines, but the M70S remains competitive for colocation-ready operations.
Compare miners by efficiency
Use our miner compare tool to see the M70, M70S, and M73 side by side, or run profitability scenarios for each model.