My $1,900 Mining Rig Cleared $41 Last Month

Three hundred two dollars and six cents. That was the rig's slice of our December Xcel bill, and I stood at the kitchen counter on January 4 with the paper in one hand and the F2Pool dashboard on my phone showing 0.00394 bitcoin earned for the month, about $343.26 at December's average price. My wife asked what the number meant. I did the subtraction twice.

The rig cost $1,900 back in October, a used Antminer S21 shipped from a farm auction in Texas, and at this rate it needs about 46 months to pay for itself, which lands in November 2029 if nothing breaks and nothin' changes. That is the honest timeline. Our garage is unheated. The bikes live in the driveway now.

The part my spreadsheet missed is a six-inch duct, a tripped breaker on the first night, and a 1,500-watt workshop heater that has not been plugged in since November 4. I am not shutting the rig down. The reasons live in the ductwork, the breaker box, and the cold corner behind the dryer.

78 decibels and a tripped breaker

The S21 arrived on a pallet: 200 terahash, about 29 pounds of aluminum and fans that pull 3,500 watts flat out. Noise at arm's length: 78 decibels on my phone's sound meter. A leaf blower that never turns off. My neighbor Ken leaned over the fence and asked if I had bought a generator. The first night it tripped the garage's 15-amp circuit inside twenty minutes, because 3,500 watts on a 120-volt house line is a physics problem rather than a preference, and the breaker won that argument instantly.

An electrician friend named Drew put in a dedicated 240-volt circuit for $340 in parts and labor, plus a case of Grain Belt that we agreed not to itemize. Worth every penny. The rig has run 2,214 hours since October 12 with one gap of nine hours, the night a firmware update needed a reboot and nobody was home to press anything.

0.00394 bitcoin for December

The whole business in six numbers. Hashrate: 200 terahash, steady. December uptime: 721 of 744 hours. Power draw: 3,500 watts, which is 2,524 kilowatt-hours at Xcel's residential rate of $0.1197, or $302.06. Pool payout: 0.00394 bitcoin, worth $343.26 at December's average price of about $87,100, which is the number I screenshot and the number my brother-in-law refuses to believe even after I showed him twice. Net for the month: $41.20.

November was better and worse at once: revenue of $361.40 on a higher average bitcoin price against $292.88 of power, for a net of $68.52 that I still do not fully trust. December, though, is the month that counts. October was 19 days of partial-month chaos and netted $12.17 after the breaker fiasco. The three-month average is $40.63, which is why I keep rounding to $41.

the six-inch duct

The upgrade that changed the math was not electronic. A six-inch insulated duct runs from the rig's exhaust box thru the garage wall into my workshop behind the washer and dryer, and the waste heat that usta dump into open air now holds that room at 58 degrees all winter. The rig makes 3,500 watts of heat, continuously. It is a space heater that happens to mine.

the heater behind the dryer

The workshop heater pulled about 450 kilowatt-hours a winter month at last year's usage, call it $54 at the old rate. It has not run since November 4. Below about 45 degrees outside the rig's heat needs help, and Drew's little oil radiator picks up the slack for an hour or two in the mornin' before the rig's heat catches up. Net of the heater we retired, December was closer to $95 in the black, and the garage has never been a better place to stand.

April 2028, circled in red

The halving is on my calendar. April 2028, the block subsidy drops from 3.125 bitcoin to 1.5625 per block, and unless price or my power rate does something heroic, revenue per terahash gets cut approximately in half overnight. Every miner alive lives with that math. My break-even date of November 2029 needs December to repeat 34 more times, and difficulty adjustments have already shaved the daily payout twice since October.

the bikes in the driveway

The family audit, since it hums in the background of every number above. My wife's rule was one sentence: it does not come in the house, and it does not touch the checking account. The rig passes both. Payouts land in a separate Coinbase account, its power cost sits inside my hobby budget next to a golf membership I let lapse, and the kids have named the thing the furnace. Ken asked for a cut of the heat for his side of the fence, which is not how any of this works, but I brought him a six-pack in December anyway.

the bill on the fridge

So, January 4, kitchen counter, the Xcel envelope with my thumb smudging the total. The rig earned $343.26 in December and cost $302.06 to run, $41.20 of that is real, and the workshop holds a steady 58 degrees because of it, which is more than the old heater ever managed. The bill is on the fridge now, between two crayon drawings. January's will be higher. The furnace hums. That is the whole business plan.