About every four years, the reward for mining Bitcoin gets cut in half. That event is called a halving, and it changes the math for every mining machine. This guide explains what a halving does, how to measure payback, and which machines are most likely to earn back their cost before the next one.

What is a Bitcoin halving?

A halving is a built-in rule that cuts the reward for mining a block in half. Bitcoin’s code does it automatically after every 210,000 blocks, which takes about four years. The last halving set the reward at 3.125 BTC per block. The next one will set it at 1.5625 BTC.

How many new coins are created each day?

A new block arrives about every ten minutes, so there are about 144 blocks a day. At the current reward, that means about 450 new coins a day. After the next halving, it will be about 225.

How does a halving change mining profit?

The network pays miners half as many coins for the same work. If the coin price and the mining difficulty stay the same, a machine’s daily revenue drops by about half. Its costs do not drop at all, because electricity still costs the same. That means profit falls by much more than half.

Why do costs matter more than revenue?

Power is a fixed bill, so it hurts more as revenue shrinks. Say a machine earns 20 units a day and uses 8 units of electricity. Its profit is 12. After a halving, revenue is 10, power is still 8 and profit is only 2. Revenue fell by 50 percent, but profit fell by more than 80 percent.

What does payback mean for a mining machine?

Payback is the time a machine needs to earn back what it cost. The formula is simple: purchase cost divided by daily profit. Daily profit is revenue minus electricity.

What does a payback example look like?

Use the same machine as above, and say it cost 3,600 units. Before a halving, payback is 3,600 divided by 12, which is 300 days. After the halving, it is 3,600 divided by 2, which is 1,800 days. The same machine takes six times longer to pay for itself. A machine that has not paid back by the halving will earn far less afterward.

Which machines are most likely to pay back in time?

The best candidates use the least power for each unit of work and run on cheap electricity. An ASIC miner is built to do one job only, so efficiency is the main thing that separates one model from another. It is measured in joules per terahash, or J/TH. Lower is better.

Is there a simple rule to follow?

Yes. If a machine spends less than half of its daily revenue on electricity, it should still earn a profit after the halving, as long as price and difficulty stay the same. If it spends more than half, it will start losing money.

How do common models compare?

The Antminer S23 Hydro runs at about 9.5 J/TH, the Antminer S21 at about 17.5 J/TH, and the older Antminer S19 XP at about 21.5 J/TH. At the same electricity price, the S23 Hydro keeps the widest margin, and the S19 XP keeps the thinnest. A newer Bitcoin miner with low power use is better placed than an older one on the same power bill.

Which machines are most at risk?

Older, less efficient machines on expensive power are the most exposed. Home electricity often costs two to three times what industrial sites pay. A machine that earns a small profit on cheap power can turn into a loss at home right after a halving.

Does a higher Bitcoin price change the answer?

It can. If the coin price doubles, revenue returns to where it was before the halving. Past price moves have sometimes offset a halving, but nobody can promise that. Planning without counting on a price rise is the safer test. Network difficulty matters too. When more machines join the network, each machine earns less.

How can you check payback for your own setup?

Start with your own numbers: the machine’s power draw, your electricity price, the current coin price, and the network difficulty. A free crypto profit calculator, such as the one from MillionMiner, does the math and updates as the market moves. Then run a second test with revenue cut in half. If the machine still shows a profit in the second test, it is more likely to pay back in time.

Should you buy before or after a halving?

Neither timing is automatically better. Buying before a halving leaves less time to earn back the cost at the higher reward. Buying after means the lower reward is already known and can be built into your math. What matters most is whether the numbers work at the lower reward.

Quick answers

How often does a halving happen?

About every four years, or every 210,000 blocks.

Does a halving make old machines useless?

No. They keep working and keep earning coins. They only stop being profitable if their electricity cost is too high compared with their revenue.

What efficiency should a machine have?

Lower is better. Machines under about 15 J/TH keep more of their revenue, but the right number depends on your electricity price.

Can payback be guaranteed?

No. It depends on coin price, difficulty, electricity cost and how long the machine runs without problems.