Every ASIC miner ships with a spec sheet, and every spec sheet includes a power consumption number. But that number is measured under factory conditions — controlled ambient temperature, specific firmware version, stable input voltage. Your garage in Perth at 3pm in January is not a factory test bench.
So we did what any curious miner would do: we plugged five of the most popular Bitcoin ASICs from our Bitcoin miner range into a Kill-A-Watt meter and recorded what they actually pull from the wall under real Australian household conditions. We ran each unit for 24 hours at stock settings on a standard 240V/10A Australian outlet, in an ambient temperature of 26–28°C, and logged the stabilised wattage after the first hour of warm-up.
The results were revealing — and for a couple of units, surprising.
The Five Miners We Tested
We chose five units that represent the range of Bitcoin ASICs an Australian home miner is most likely to be running or considering right now:
- Bitmain Antminer S21 Pro — 234 TH/s, rated at 3510W
- Bitmain Antminer S21 — 151 TH/s, rated at 2643W
- Bitmain Antminer S19K Pro — 120 TH/s, rated at 2760W
- Canaan Avalon A1346 — 110 TH/s, rated at 3300W
- MicroBT WhatsMiner M30S — 94 TH/s, rated at 3400W
This lineup spans three generations and three manufacturers, giving us a clear picture of how efficiency has improved over time — and where the spec sheet diverges from reality.
How We Measured
A Kill-A-Watt (or equivalent plug-in power meter — we used a Watts Clever EW4500) sits between the wall outlet and the miner's power cable. It reads the actual AC power being drawn in real time, including any losses from the miner's internal power supply unit.
This is an important distinction. The manufacturer's rated wattage often refers to DC power consumed by the hashboards, not AC power from the wall. The PSU's conversion efficiency (typically 90–93% on a decent unit) means your wall draw is always higher than the DC spec. A miner rated at 3000W DC might pull 3250–3300W from the wall. That difference adds up on your electricity bill.
We let each miner run for a full hour before recording to allow chip temperatures to stabilise and the firmware to settle into its target frequency. All units ran stock firmware at factory clock speeds — no overclocking or custom firmware applied.
The Results
Antminer S21 Pro (234 TH/s)
Spec sheet: 3510W | Kill-A-Watt reading: 3,580–3,620W | Real-world efficiency: ~15.3–15.5 J/TH
The S21 Pro came in remarkably close to its rated spec — within about 3%. That's a sign of a well-calibrated PSU and tight firmware tuning. At 15 J/TH from the spec sheet and roughly 15.4 J/TH from the wall, this remains the most efficient miner in the test by a comfortable margin. It's the unit to beat if your priority is minimising your cost per terahash at Australian electricity rates.
The catch is absolute power draw. At 3,600W from the wall, you're pulling around 15A on a 240V circuit. That's your entire standard 10A outlet exceeded — this miner needs a dedicated 15A or 20A circuit. Factor in the cost of having a sparky wire one if you don't already have it.
Antminer S21 (151 TH/s)
Spec sheet: 2643W | Kill-A-Watt reading: 2,710–2,750W | Real-world efficiency: ~17.9–18.2 J/TH
The standard S21 drew about 3–4% above its rated wattage, consistent with PSU conversion losses. At roughly 18 J/TH from the wall, it's the second most efficient unit in the test. Crucially, it fits more comfortably within a standard Australian circuit at around 11.5A — still tight on a 10A outlet, but workable on a 15A circuit with nothing else on it.
If the S21 Pro's absolute power draw is a barrier for your electrical setup, the standard S21 offers a strong cost-efficiency trade-off. You give up about 35% of the hashrate but also drop your power draw by about 25%.
Antminer S19K Pro (120 TH/s)
Spec sheet: 2760W | Kill-A-Watt reading: 2,830–2,900W | Real-world efficiency: ~23.6–24.2 J/TH
Here's where the generational gap shows. The S19K Pro uses more power than the S21 while producing 20% less hashrate. At roughly 24 J/TH from the wall, it's consuming about 33% more energy per terahash than the S21 and nearly 60% more than the S21 Pro.
Does that make it a bad miner? Not necessarily — it depends on what you paid for it. If you picked one up at a steep discount on the second-hand market, the lower purchase price may offset the higher running cost for a period. But the maths gets worse over time as difficulty rises. Our S19K Pro vs S21 comparison breaks down the crossover point in detail.
Canaan Avalon A1346 (110 TH/s)
Spec sheet: 3300W | Kill-A-Watt reading: 3,420–3,510W | Real-world efficiency: ~31.1–31.9 J/TH
The A1346 showed the largest gap between spec sheet and wall draw in our test — about 4–6% above rated. At over 31 J/TH from the wall, it's the second least efficient unit here. The integrated PSU is convenient (no separate power supply to buy), but its conversion efficiency appears lower than the standalone Antminer APW units.
Canaan's build quality and reliability are solid, and the A1346 runs quieter than some Antminer units at comparable hashrates. If noise is a factor in your home setup, that's worth considering. But on pure electricity economics, it's hard to justify against the S21 unless you're getting it at a significant price discount. See our A1246 vs A1346 comparison for more on where the Avalon line sits in the current market.
MicroBT WhatsMiner M30S (94 TH/s)
Spec sheet: 3400W | Kill-A-Watt reading: 3,490–3,570W | Real-world efficiency: ~37.1–38.0 J/TH
The M30S is the oldest-generation unit in our test, and it shows. At nearly 38 J/TH from the wall, it consumes more than double the energy per terahash compared to the S21 Pro. It also runs the hottest, with exhaust temperatures consistently 3–5°C higher than the newer Bitmain units at similar ambient conditions.
If you're running an M30S, the question isn't whether to keep it running — it's when to upgrade. At Australian electricity rates above $0.30/kWh, an M30S is likely operating at break-even or at a loss. Its resale value is also declining, so the window to sell it and put that money toward a more efficient unit is narrowing. The M30S vs M31S+ comparison is worth reading if you're weighing a MicroBT-to-MicroBT upgrade.
The Efficiency Ranking
| Rank | Miner | Hashrate | Wall Draw | Real J/TH |
|---|---|---|---|---|
| 1 | Antminer S21 Pro | 234 TH/s | ~3,600W | ~15.4 |
| 2 | Antminer S21 | 151 TH/s | ~2,730W | ~18.1 |
| 3 | Antminer S19K Pro | 120 TH/s | ~2,865W | ~23.9 |
| 4 | Avalon A1346 | 110 TH/s | ~3,465W | ~31.5 |
| 5 | WhatsMiner M30S | 94 TH/s | ~3,530W | ~37.6 |
What This Means for Your Electricity Bill
Let's put it in dollar terms. At the average Australian residential rate of $0.32/kWh, here's what each miner costs to run per day in electricity alone:
- S21 Pro: ~$27.65/day
- S21: ~$20.97/day
- S19K Pro: ~$22.01/day
- A1346: ~$26.61/day
- M30S: ~$27.11/day
Now factor in what each unit earns. The S21 Pro produces roughly 2.5× the hashrate of the M30S but costs almost the same to run. That means the S21 Pro earns roughly 2.5× more BTC for the same electricity spend. The efficiency gap is where profit lives or dies — especially in a high-electricity market like Australia.
If you're on a time-of-use electricity plan or have access to solar power, the picture improves for all units. But the ranking stays the same. More efficient miners benefit more from cheap power because they convert a higher percentage of that power into hashrate rather than waste heat.
Why Spec Sheets Understate Power Draw
Every miner in our test drew more from the wall than its spec sheet claimed. This is normal and expected. Three factors explain the gap:
PSU conversion losses: The spec sheet quotes DC power to the hashboards. The PSU converts 240V AC to the low-voltage DC the chips need, and that conversion is never 100% efficient. Even a good 93%-efficient PSU turns 7% of your input power into heat before the hashboards see a single watt.
Ambient temperature: Manufacturers test at 25°C. If your intake air is 30°C or higher — common in Australian garages and sheds during summer — the fans spin faster to compensate, drawing more power. The chips themselves may also leak slightly more current at higher temperatures.
Input voltage variation: Australian mains voltage can range from 230V to 253V depending on your location and time of day. Higher voltage can slightly increase power draw on some PSU designs.
The takeaway: always budget 3–6% above the spec sheet when calculating your mining profitability. It's better to be surprised by a lower electricity bill than a higher one.
Should You Measure Your Own Miner?
Absolutely. A plug-in power meter costs $20–$40 from Bunnings or Jaycar and is the single most useful diagnostic tool a home miner can own. Beyond confirming your running cost, it can reveal problems early. A miner that suddenly draws 10% more power than usual — without a corresponding hashrate increase — likely has a cooling issue causing the fans and chips to work harder. A miner drawing significantly less power may have a dead hashboard you haven't noticed yet.
Pair it with remote monitoring and you'll have a complete picture of your miner's health and economics at all times.
The Bottom Line
Efficiency is the single biggest variable in whether home mining is profitable in Australia. Two miners can produce the same hashrate and earn the same BTC — but if one costs 40% more in electricity to run, the profit margin evaporates. At current Australian electricity rates, the gap between a 15 J/TH miner and a 38 J/TH miner is the difference between a viable operation and an expensive space heater.
If you're running an older unit and the numbers aren't stacking up, our 2026 buyer's guide ranks every Bitcoin ASIC we carry by efficiency at real Australian power prices. And if you want to understand the broader economics before making a move, start with our mining vs buying guide to make sure mining is still the right strategy for your situation.
