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Field report · Oct 3, 2026 · 4 min read

Two years in the UAE, the Whatsminer M66S has never needed to move or switch off

MicroBT launched the M66S in October 2023 as an 18.5 J/TH immersion machine. We bought one in June 2024, two months after the halving, and racked it in the UAE. Difficulty has risen by more than half since, and the machine has stayed where it started, hashing.

Firsthand card: "Two years in the UAE, the Whatsminer M66S has never needed to move or switch off", the machine's store photo beside its 18 J/TH, 310 TH/s, immersion-cooled spec

MicroBT Whatsminer M66s (310 TH/s)

Bought eight months after launch, two months after the halving

MicroBT unveiled the M66S at Blockchain Life in Dubai on 26 October 2023, as the immersion-cooled machine of its M60 generation. In the launch release the M66S ran from 270 to 298 TH/s at 18.5 J/T. Ours is a 310 TH/s bin drawing 5,580 W, which our catalogue puts at 18 J/TH, a little better than the figure quoted at launch.

We bought it on 24 June 2024 at $5,892 and landed it at our UAE site for $7,781, 32% more than the machine alone. The UAE is where immersion and hydro machines start, and the price of a miner is not the price of the box. It began hashing two months after the April 2024 halving, so it had no months at the old subsidy to bank.

There is no owner record of this model that we could open and quote, so how its boards age over a full working life is unknown, and we treat it as unknown rather than good. What a fault costs is a line item, not a catastrophe.

Chart: What an M66S has cost over the time we have tracked it. We bought in June 2024; the entry price has settled well below that since.

The network's difficulty rose 59% while it ran

On 24 June 2024, the day we bought it, difficulty stood at 83.7 trillion. On 2 October 2026 it was 132.8 trillion. Bitcoin rose too, up 38% over the same stretch, but not by enough to hold what a unit of hashrate earns.

A petahash made 0.000782 BTC a day on 24 June 2024 and 0.000478 on 2 October 2026: 39% fewer coins for the same hashrate. That is the test a machine of this age was bought to pass. It is not asked to earn more each year. It is asked to keep making coins while its share of each block shrinks, which is what efficiency decides.

A petahash earned 39% fewer coins a day than when we bought. The machine kept making them.

Chart: Hashprice, the dollars one petahash earns in a day, since the month we bought. It reached its low for the run, $27.74, on 6 June 2026. Open the chart

It cleared its power at the low, and it has not moved

The bottom came on 6 June 2026, when a petahash earned $27.74 a day, the lowest reading of this machine's run. At 18 J/TH a petahash draws 432 kWh a day, so that day paid for power priced up to about 6.4¢ a kilowatt-hour, before any pool fee. The UAE rate is 6¢.

That is a thin margin, not a comfortable one, and it held. 0 of its 832 days have been idle: no day came when nothing we host would have paid for its power. At the prices of each month it cleared its electricity every month. The thinnest were all in 2026, and the best were in late 2024 and mid-2025.

Nigeria would make the same coin for about $37,000 of electricity, against $57,000 here, because power there costs a third less, but its uptime is lower. The rule is to cross to Nigeria once, when a full trailing year says cheap power is decisively better. For this machine that has not happened in 832 days.

At 18 J/TH it sat above the power line at the worst reading of its run.

Chart: Profit over electricity, month by month, at the UAE site where it has run throughout. Every bar is above zero; the shortest are in 2026.

The tally, and what is left in it

In 832 days it has mined and kept 0.1376 BTC, worth $11,673 today, for $6,970 of electricity. Averaged over its life that is $50,700 a coin. Treat that as history: the number to plan on is today's, about $57,000 at the UAE rate, against bitcoin at $84,643.

That is $4,702 of cashflow, or 60% of its $7,781 landed cost, a little over half way through a four-year working life. Between now and the April 2028 halving it has another 0.083 BTC in it at today's difficulty, worth about $10,343 with bitcoin back at its previous high of $124,493. That high is an assumption, not a forecast. It puts the machine at 1.9× its hardware by the halving, still running at the end of it.

Chart: Coins kept, the electricity that made them, and where it lands by the 2028 halving.

The same chassis got better twice

MicroBT kept improving this immersion machine. Our catalogue lists the M66S+ from July 2024 at 17 J/TH and the M66S++ from December 2024 at 15.5 J/TH, the second now sold out.

The M66S+ at 318 TH/s lists today at $2,437. In the UAE it makes a coin for about $53,800 of electricity, against $57,000 for ours. The same site, the same tank, and more coins from every kilowatt-hour.

The machines that make a coin for less electricity than this one does today.

What it means for a miner

The output of this machine has not changed in two years. What changed is the entry price: the same machine in its 302 TH/s bin lists at $2,220, the best entry it has had, and the machine has now been through a 59% rise in difficulty and a hashprice low without a day off.

If you are buying, buy for the halving in front of you. At 18 J/TH the margin at 6¢ was thin in 2026, and efficiency is where more of it comes from, so the S21 Immersion and the M66S+ are the places to look first. If you already own one, keep the coins: nobody sells them to pay the power bill.

Sources and further reading

Which machines this covers

Disclosure

Firsthand Bitcoin sells and hosts mining hardware, including this machine. No manufacturer, distributor or affiliate programme paid for or reviewed this page and we take no commission on the links above. Historical figures are computed from daily bitcoin price and network hashprice, each day valued at its own prices. Nothing here is investment advice.