I Bought a Used Antminer on Facebook Marketplace Last summer, I found an An

I Bought a Used Antminer on Facebook Marketplace

Last summer, I found an Antminer S9 for $320 on Facebook Marketplace. The seller said it "worked great, just upgrading." I didn't know what I was doing. I had a vague idea that Bitcoin mining was basically free money if you had the machine. I had the machine. I had a garage outlet. I handed over $320 in cash and loaded the thing into my trunk.

The miner weighed thirty pounds and sounded like a hair dryer duct-taped to a jet engine. My wife asked if I was starting a laundromat. I said I was "exploring passive income." She looked at me the way she looks at me when I say I'm going to fix the sink myself.

Setup Took Two Days and $47 in Cables

Getting the S9 running was harder than the seller made it sound. I needed a dedicated 220V outlet—my garage only had 110V. An electrician quoted me $400 to add a line. I said no thanks and instead ran an extension cord from the dryer outlet in the laundry room through the garage window. Cost me $47 for a heavy-duty cord at Home Depot. It was ugly, but it worked.

I connected the miner to my wifi via an Ethernet bridge, pointed it at Slush Pool, and created an account. The dashboard showed my hashrate fluctuating between 13 and 14 terahashes per second. The S9's rated speed was 14 TH/s, so I was close. I felt genuinely proud when I saw my first "share accepted" message scroll past on the miner's debug screen.

Then I got my first electric bill.

The Bill That Ended the Dream

My monthly electricity bill averaged $127 before the miner. The first full month with the S9 running 24/7, it hit $312. The miner was drawing about 1,300 watts continuously. At my local rate of $0.14 per kilowatt-hour, that was $131 per month in electricity alone. I was mining about 0.00035 BTC per day. At the August price of roughly $26,000 per BTC, that was $9.10 per day, or $273 per month in gross revenue.

So my net profit was $273 minus $131, or $142 per month. But that was before cooling. The garage got so hot—regularly over 95°F—that I bought a $68 window exhaust fan. And the noise was unbearable. I eventually moved the whole setup to the basement utility room, which meant buying another $23 in longer Ethernet cables and a power strip. My running costs kept creeping up.

Six Month Final Accounting

I ran the miner for exactly six months before selling it. Here's the honest math:

Revenue: 0.0634 BTC mined total. At average price during the period, approximately $1,647 worth.

Costs: $320 for the used miner. $131/month × 6 months = $786 in electricity. $47 for the initial extension cord. $68 for the exhaust fan. $23 for cables and accessories. $45 for Slush Pool fees over six months. Total costs: $1,289.

Net result before selling: $1,647 revenue minus $1,289 costs = $358 profit over six months. Or about $59 per month for running a machine that sounded like a dying robot in my basement.

Then I sold the S9 on eBay for $180. It was still working fine, but Bitcoin's difficulty had increased and my margin was shrinking every month. My final adjusted profit: $358 plus $180 resale, minus $28 in eBay fees and shipping, equals $510 total. Over six months, that's about $85 per month.

What I Actually Learned

Bitcoin mining at home with outdated hardware is technically profitable, but only barely. The margins are thin, the noise is real, and the heat is worse than you expect. Every month the network difficulty increases, your same machine earns less. My S9 was already several generations behind when I bought it. Within two months, my daily earnings had dropped from $9.10 to $7.80. The trend was clear.

The real value wasn't the $510. It was the education. I now understand hashrate, difficulty adjustment, pool fees, power efficiency, and why modern mining operations are located near cheap hydroelectric dams. I also understand why my little garage experiment was never going to scale. The economics of industrial mining—custom chips, $0.03/kWh power, climate-controlled warehouses—are completely different from home mining.

If someone asked me today whether they should try home Bitcoin mining, I'd say this: don't do it for the money. Do it only if you're genuinely curious about how the network works and you're willing to spend $500-$1,000 on an education that happens to involve a loud machine. If you want passive income, buy $500 of BTC on Coinbase or Kraken and hold it. You'll probably end up with more money and significantly less noise.

My Antminer is gone now. The garage is quiet again. My dryer outlet is back to its intended purpose. And every time I see a headline about a new mining farm in Kazakhstan or Texas, I nod and think: yeah, that makes sense. That absolutely makes sense.