What TH/s, J/TH and uptime mean, how they differ, and where to see each one for your own machines.
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Three numbers describe almost everything about a mining machine: how much work it does, how much electricity it needs for that work, and how much of the time it is running. Once you can read them, you can compare any two machines and follow your own with confidence.
Mining is guessing. A machine tries numbers until one produces a valid block, and each try is a hash. Hashrate is how many tries it makes per second. Today's machines make trillions, so the unit is the terahash per second, written TH/s.
| Unit | Equals | Where you meet it |
|---|---|---|
| TH/s | One trillion hashes per second | One machine |
| PH/s | 1,000 TH/s | A group of machines, and hashprice quotes |
| EH/s | 1,000,000 TH/s | The whole Bitcoin network |
More hashrate means a larger share of the work, and so a larger share of the bitcoin a pool pays out. Twice the hashrate, running for the same time, earns about twice as much.
The rated hashrate is the manufacturer's figure for the model. The delivered hashrate is what the machine does on a given day. The two are never exactly equal:
Good to know: Judge a machine on its average over a day or a week, never on one reading.
Efficiency is the energy a machine uses for each terahash, written in joules per terahash: J/TH. Lower is better. You will also see W/TH, watts per terahash per second. It is the same number, because one watt is one joule per second.
A spec sheet lists three figures that belong together: hashrate, power draw and efficiency. Efficiency is the power draw divided by the hashrate. Two machines with the same hashrate do the same work, but the one with the lower J/TH needs less electricity to do it.
Efficiency is what separates generations of machines. Each new generation does the same work with less energy. That is why efficiency matters more as a machine ages: when mining income per terahash falls, the machine that needs the least electricity keeps the widest margin.
Uptime is the share of time a machine was hashing. A machine that ran 27 days out of 30 had 90% uptime. A machine earns only while it runs, so uptime scales its output directly.
Uptime depends on the machine and on the site: power cuts, network outages, heat, and the time it takes to replace a part. No site and no machine runs 100% of the time over years.
| Number | Unit | Better when | It drives |
|---|---|---|---|
| Hashrate | TH/s | Higher | How much bitcoin the machine can mine |
| Efficiency | J/TH | Lower | How much electricity that work needs |
| Uptime | % | Higher | How much of the time it is mining |
A machine with a high hashrate and poor efficiency mines a lot and uses a lot. A very efficient machine at a site with poor uptime leaves part of its capacity unused. Look at all three before you compare two offers.
Careful: Mining output depends on bitcoin's price, network difficulty and uptime, and is not guaranteed. Nothing here is investment advice.