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Progress report · Nov 11, 2026 · 4 min read

Twenty months in the UAE, never off: the Whatsminer M66S++ clears its line by $10 a petahash

The M66S++ went into the tank in March 2025, when a petahash earned twice its power bill, and has not had a day off since. Hashprice has never come within $5 of its line, even at June's low. The 2028 halving is what sends it to Nigeria, and the trailing year decides when.

A Whatsminer M66S++, the real store photograph of the machine whole, on a cool slate-teal studio backdrop

MicroBT Whatsminer M66S++ (348 TH/s)

Bought in March 2025, when a petahash earned twice its power bill

The M66S++ is MicroBT's immersion machine of the M6x generation: 348 TH/s from 5,394 W in our store record, 15.5 J/TH, announced in December 2024. MicroBT's own shop page gives 267.5 × 147 × 401 mm with the handle, 18 kg net and a 380–480 V supply, and nothing else we could use, so the hashrate and power here are the store record's. It is the step up from the M66S at 18 J/TH and the M66S+ at 17, in the same tank-cooled chassis.

The first price we hold for it is from 14 March 2025: $5,986, or $7,535 landed in the UAE, where immersion machines start. Hashprice, what a petahash earns in a day, was $47.16 that day. At 15.5 J/TH a petahash uses 372 kWh a day, $22.32 at the UAE's 6¢, so the machine went in with its power bill covered a little over twice.

Chart: Coins kept since 14 March 2025, the electricity that made them, and where it lands by the 2028 halving at today's conditions. One site, no moves.

Hashprice never came within $5 of its line

A machine's line is the hashprice at which it stops covering its own power, and the engine switches a machine off when the trailing month no longer pays it. In 608 days the M66S++ has been off for 0. Over that run hashprice peaked at $63.80 on 11 July 2025 and bottomed at $27.74 on 6 June 2026, which was still $5.42 above the line. On 10 November it was $32.10, $9.78 above.

Its sibling at 18 J/TH, the M66S, has a line of $25.92 at the same rate and has had the same quiet two years. The difference between them is about $3.60 of margin on every petahash every day, and it is the whole reason the ++ exists.

The low was $27.74 on 6 June 2026. The line is $22.32. The machine did not notice.

Chart: Network hashprice per petahash per day since the purchase. The M66S++'s line is $22.32 at 6¢ and $14.51 at 3.9¢; the June 2026 low of $27.74 stayed above the first. Open the chart

What it has banked

Over 608 days the M66S++ has mined and kept 0.0998 BTC for $4,924 of electricity, about $49,300 a coin as a lifetime average at 6¢. At today's price the coins are worth $7,508, which is $2,584 of cashflow after every power bill and 34% of the $7,535 landed cost: 0.3× through the box, twenty months into a four-year life.

At today's difficulty, with bitcoin back at its previous high, it has another 0.078 BTC in it between now and April 2028, worth about $9,657. That puts it near 1.6× its full landed cost by the halving, with the machine still running. Today a coin costs it about $54,900 of electricity in the UAE and about $35,700 in Nigeria, against $74,198 to buy one.

Chart: Profit over electricity, month by month, every month at the UAE's 6¢.

The halving is what moves it, and the trailing year says when

The 2028 halving halves the coins a petahash earns. At today's price and difficulty that puts hashprice near $16.05, under the $22.32 line at 6¢ and $1.54 above the $14.51 line at Nigeria's 3.9¢. That is today's conditions held flat, not a forecast; every projection we publish assumes the old high returns. What it says is that this machine's one move is ahead of it, and it is the halving, not the market, that makes cheaper power the better home.

The move does not happen on halving day. A machine crosses to cheap power once, when a trailing year of its own figures says Nigeria would have paid it decisively more, so the crossing comes when the year's numbers say so and then stays. Until then, 99.3% uptime at 6¢ is the better deal for a machine clearing its line by nearly $10 a day per petahash.

Chart: The electricity behind each coin against the market price, at the site the machine was at. The gap is what a miner who keeps the coins is paid.

What a fault costs here

MicroBT's immersion cooling operation guide uses the M66S++ as its example machine, and the thing specific to a tank is the fluid itself. A repair shop's troubleshooting page for the Whatsminer tank-level warning puts the first step plainly: "Visually confirm the actual fluid column on the sight glass before doing anything else." On a hosted machine that check is ours, not yours.

We found no operator thread on the ++ itself, so its record is the twenty months above and nothing more. In the UAE a manufacturer warranty centre sits close to the facility, and a failed hashboard is a line item, not a catastrophe.

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.