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One Bitmain Antminer S21 is a continuous 3.5 kW load. At full uptime it uses about 84 kWh per day (30,660 kWh per year), before cooling, networking, electrical losses, hosting, repairs or downtime. At an electricity tariff of $0.06/kWh, that energy costs about $5.04 per day; at $0.10/kWh, $8.40; and at $0.15/kWh, $12.60. Those are bill calculations, not profitability forecasts.
Bitcoin mining breaks even only when expected mining revenue covers the complete operating cost. The electricity-only test is break-even $/kWh = expected mining revenue per day ÷ daily kWh. Because revenue changes with bitcoin’s price, network difficulty, block subsidy, transaction fees, pool fees and uptime, there is no permanent “profitable electricity rate.” Use your current tariff and current network data, then include every facility cost before deciding whether to run or shut down a miner.
How much electricity does a Bitcoin miner use?
Use the miner’s wall-power rating, not the lower chip-only figure. Wall power is what your electrical service must deliver and what your meter records. The Bitmain Antminer S21 specification lists 200 TH/s hashrate, 3,500 W wall power and 17.5 J/TH efficiency on a 220–277 V input. Bitmain describes these as typical values; actual hashrate and power can vary around the specification.
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- Please kindly note that the required input voltage for Bitmain Antminer S21 is 220V-277V. Wrong input voltage may probably cause miner damaged
- Continuous load: watts ÷ 1,000.
- Daily energy: continuous kW × 24 × uptime fraction.
- Billing-period energy: daily kWh × the number of days in the billing period.
- Energy charge: kWh × the delivered tariff, plus demand charges, taxes and fixed charges.
For an S21, 3,500 W ÷ 1,000 = 3.5 kW. Running continuously for 24 hours uses 3.5 × 24 = 84 kWh per day. At 365 days and 100% uptime, that is about 30,660 kWh per year. A 95% uptime assumption would reduce the energy calculation to 79.8 kWh per day, but it would also reduce mining revenue.
S21 electricity-cost examples
The table below applies only the stated energy rate to one S21’s 84 kWh daily use. It excludes demand charges, taxes, cooling, hosting, repairs, financing and all other operating costs.
| Delivered energy rate | Daily energy cost | 30-day energy cost | 365-day energy cost |
|---|---|---|---|
| $0.06/kWh | $5.04 | $151.20 | $1,839.60 |
| $0.10/kWh | $8.40 | $252.00 | $3,066.00 |
| $0.15/kWh | $12.60 | $378.00 | $4,599.00 |
These figures assume 100% uptime and a 30-day month for the monthly column. Your bill may use a different number of days, a time-of-use schedule or a demand component. Multiply the miner count by the same calculation only after checking whether your tariff or site overhead changes at a larger load.
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An S21 draws approximately 3.5 kW continuously. The input voltage range specified for that model is 220–277 V, so it is not a normal 120 V household appliance. The current depends on voltage and power factor: at 240 V, 3,500 W is roughly 14.6 A before power-factor and design-margin considerations. Have a qualified electrician select conductors, breakers, receptacles, disconnects, transformers and panels for the measured equipment load and the electrical code in your jurisdiction.
Do not size a circuit by adding nameplate watts and assuming a receptacle can run at that value indefinitely. Continuous loads generally require code-mandated ampacity and breaker margins, and local rules differ. A panel, feeder or transformer that can start a load briefly may still overheat under a 24-hour mining load. Use listed equipment, proper over-current protection, grounding, cable ratings, ventilation clearances and an accessible disconnect.
For multiple miners, add the wall-power ratings first:
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- The Hashrate value, Power on wall, and Power efficiency on wall are all typical values, The actual Hashrate value fluctuates by ±3%, and the actual Power on wall and Power efficiency on wall fluctuate by ±5%.
- Caution: Wrong input voltage may probably cause server damaged.
- Two S21 units: about 7.0 kW continuous and 168 kWh per day.
- Ten S21 units: about 35 kW continuous and 840 kWh per day.
- One hundred S21 units: about 350 kW continuous and 8,400 kWh per day.
Those totals cover miners only. Fans, pumps, air-conditioning, immersion-cooling equipment, network hardware, lighting and control systems add site load. A facility also needs enough service capacity for startup behavior, maintenance bypasses and any other simultaneous customer load.
What your electricity tariff really includes
A quoted cents-per-kilowatt-hour number is often not an all-in mining cost. Request the tariff sheet or bill and separate each component:
- Energy charge: the variable price per kWh or MWh.
- Demand charge: a fee based on the highest kW during a billing interval, or on a coincident system peak.
- Time-of-use periods: different prices by hour, weekday or season.
- Transmission and distribution: network delivery charges that may be bundled or itemized.
- Taxes and regulatory riders: jurisdiction-specific additions.
- Fixed customer charges: monthly fees that matter more when the site is small.
- Hosting or colocation fees: charges that may include power, space, labor, security and internet service.
- Curtailment terms: credits or discounts in return for turning equipment off during grid stress.
For a serious estimate, convert all recurring items into a comparable $/kWh figure using the expected monthly consumption. A $0.06/kWh energy rate can be more expensive than it appears if a large demand charge is triggered by a short peak. Conversely, a higher energy rate with no demand charge may suit a small installation better than an industrial tariff.
Electricity-only break-even rate
The basic calculation is:
break-even $/kWh = expected mining revenue per day ÷ daily kWh
Use revenue expected for the same period as the energy calculation. Expected daily revenue depends on your hashrate, network difficulty, block subsidy, transaction fees, bitcoin price, pool fee and uptime. For an S21 at 84 kWh per day, every $1 of daily revenue supports about $0.0119/kWh of electricity-only cost ($1 ÷ 84). If expected revenue were $10 per day, the electricity-only break-even rate would be about $0.119/kWh. If it were $15, the result would be about $0.179/kWh; at $20, about $0.238/kWh. These are arithmetic examples, not predictions of what an S21 will earn.
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1Clear out junk files and repair common Windows errors2Fix the driver behind crashes, sound loss and screen glitches3Repair Windows errors before they cause bigger problems| Illustrative expected revenue | Daily energy assumption | Electricity-only break-even |
|---|---|---|
| $10/day | 84 kWh/day | $0.119/kWh |
| $15/day | 84 kWh/day | $0.179/kWh |
| $20/day | 84 kWh/day | $0.238/kWh |
The result changes immediately when difficulty rises, bitcoin falls, fees change, a block-reward event occurs, a pool changes its payout terms or the miner is offline. A rate that passed this test last month can fail it today. Recalculate with current inputs rather than publishing or relying on a single universal threshold.
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From electricity break-even to full operating break-even
Electricity-only break-even answers one narrow question: can mining revenue pay the energy bill? Full operating break-even asks whether the operation covers every cash and economic cost. Add the following to your model:
- Cooling energy and cooling-system maintenance.
- Power-usage-effectiveness overhead from pumps, fans, controls and distribution equipment.
- Transformer, power-supply and wiring losses.
- Pool fees and payment or transaction costs.
- Hosting, rent, internet, security and monitoring.
- Repairs, spare parts, labor and shipping.
- Hardware purchase price, expected service life and depreciation.
- Financing interest, insurance, taxes and accounting.
- Downtime, curtailment and the revenue lost while equipment is unavailable.
Model these as fixed costs, variable costs or per-kWh costs. Then calculate:
full break-even revenue per day = energy cost + overhead per day + hardware and financing cost per day
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Only compare expected mining revenue with that complete figure. A miner can be cash-flow positive against the energy bill while still failing to recover hardware capital, hosting fees or financing costs.
Why efficiency matters as much as the tariff
Efficiency is expressed in joules per terahash (J/TH). Lower is better because the machine uses fewer joules to perform the same amount of hashing. The S21’s typical 17.5 J/TH figure is a hardware benchmark; it does not include a building’s cooling or electrical overhead.
Compare candidate machines on at least five axes:
| Decision axis | Questions to answer |
|---|---|
| ASIC efficiency | What is the manufacturer’s J/TH at the intended operating mode, and how does power change when underclocked or overclocked? |
| Energy price | Is the quoted figure delivered, all-in, hosted, wholesale or retail? Are demand charges included? |
| Reliability | What uptime is realistic after outages, repairs, firmware work and grid curtailment? |
| Cooling and infrastructure | Can the site reject the heat, and what extra kW do fans, pumps or air-conditioning consume? |
| Full cost | What are the hardware, labor, hosting, financing, tax and insurance costs over the planned life? |
Changing operating mode can trade hashrate for efficiency. Any lower-power setting must be evaluated with its resulting hashrate, temperature, fan use, warranty conditions and revenue. A nominally efficient miner can lose money if it spends too many hours offline or requires an expensive cooling system.
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Cooling and heat-management load
Almost all electricity delivered to an ASIC becomes heat. A 3.5 kW miner therefore releases roughly 3.5 kW of heat while operating, in addition to heat from power supplies and site equipment. Air-cooled installations need a path for hot air to leave and cooler air to enter; recirculation raises temperatures and can cause throttling or shutdowns.
Cooling overhead can be modest in a suitable climate with well-designed ducting, or substantial when mechanical refrigeration is required. Immersion systems replace some fan noise and may improve heat handling, but pumps, heat exchangers, fluids and maintenance add capital and operating cost. Express facility overhead with a measured or modeled power-usage-effectiveness factor:
site kWh = miner kWh × PUE
A PUE of 1.10 would turn 84 kWh of miner consumption into 92.4 kWh of site consumption. Use the site’s measured value when available; do not assume a generic PUE applies to every climate or cooling design.
Uptime, outages and curtailment
Mining revenue is earned only while the ASIC is hashing and connected to its pool. Schedule maintenance, internet outages, rejected shares, firmware updates, thermal throttling and grid interruptions in the uptime assumption. A tariff that offers a large discount for interruptible service may be attractive only if the lost mining hours and restart behavior are worth the savings.
The U.S. Energy Information Administration describes cryptocurrency mining as a flexible load in some markets. Operators may participate in demand-response programs or curtail during system peaks. The correct comparison is not simply the discounted rate; it is:
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- mining revenue forgone during those hours;
- any curtailment payment or credit;
- restart time, wear and operational complexity;
- whether the program can call events during bitcoin price spikes.
Get the event rules in writing. A program that can interrupt power without notice may make a high-revenue period unavailable, while a predictable seasonal schedule may be easy to model.
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Network-scale electricity context
Electricity is the dominant operating expense for many miners. The Cambridge Centre for Alternative Finance reported in 2025 that electricity accounted for over 80% of miners’ cash-based operational expenses. Its survey estimated a median electricity cost of $45/MWh and a median all-in cost of $55.5/MWh. Those are survey results, not a guaranteed rate for a particular site.
The same 2025 Cambridge work estimated annual Bitcoin-mining electricity consumption at 138 TWh, approximately 0.54% of global electricity use in its survey-based estimate. The survey covered 49 mining firms representing about 48% of network hashrate at data collection, so the estimate should be read with its methodology and uncertainty in mind. It also reported 52.4% sustainable energy among surveyed miners; that percentage describes the surveyed group and is not a universal grid mix.
The U.S. Energy Information Administration estimated cryptocurrency mining at 0.6% to 2.3% of U.S. electricity consumption in 2024. EIA notes that facilities can relocate, may resemble other large electricity customers and use power both for machines and cooling. Large sites can require hundreds of megawatts, which is why local grid capacity, interconnection queues and demand-response rules matter as much as the advertised energy price.
A step-by-step mining electricity estimate
- Record the wall-power rating. Use the manufacturer’s typical or maximum value for the exact model and operating mode. Do not substitute chip power.
- Convert to continuous kW. Divide watts by 1,000. For a 3,500 W S21, the result is 3.5 kW.
- Set a realistic uptime. Multiply by the expected fraction of time hashing, including maintenance and curtailment.
- Calculate kWh. Multiply kW × 24 × uptime for daily use, then multiply by billing-period days.
- Apply the complete tariff. Add energy, demand, time-of-use, transmission, taxes and fixed charges. Convert fixed charges to an equivalent monthly or daily cost.
- Add site overhead. Include cooling, pumps, fans, networking, transformers, power losses and other facility consumption. Use measured PUE when possible.
- Estimate mining revenue. Use current hashrate, network difficulty, block subsidy, transaction fees, bitcoin price, pool fee and uptime. Record the timestamp because each input changes.
- Calculate both break-even tests. Divide expected revenue by miner kWh for electricity-only break-even, then compare revenue with the complete daily operating cost.
- Stress-test the result. Recalculate for a lower bitcoin price, higher difficulty, lower uptime, a higher tariff and a major repair. A thin margin can disappear under one unfavorable change.
- Check the physical installation. Confirm voltage, phase, breaker and conductor capacity, heat rejection, noise limits, internet reliability, fire protection and local permits with qualified professionals.
When should you shut down a miner?
Use a documented operating rule rather than reacting to a headline price. Shut down or curtail when expected revenue after pool fees is below the complete incremental cost of running the machine, provided the shutdown does not create a larger contractual or restart cost. For a hosted miner, that means comparing revenue with the host’s power and service charge, not just the energy component.
Keep a separate capital-recovery calculation. If revenue covers electricity and hosting but never recovers the miner’s purchase price, the operation is not economically sustainable over the planned hardware life. Conversely, a temporary electricity-only loss may be rational if a contractual curtailment credit, a fixed hosting commitment or a specific recovery plan changes the full-cost result.
Common calculation mistakes
- Using a desktop-PC estimate: a dedicated ASIC is a continuous industrial load, not an occasional household appliance.
- Using chip watts: the electrical service sees wall power, including the power supply.
- Multiplying a retail rate by kWh and stopping: demand charges, taxes, cooling and hosting can dominate the difference.
- Assuming 100% uptime: outages, repairs, network failures and curtailment reduce both consumption and revenue.
- Quoting a permanent profitable rate: break-even moves with price, difficulty, fees, subsidy and hardware efficiency.
- Ignoring heat: every mining watt becomes heat that must be removed safely.
- Overloading a household circuit: continuous high-current loads require code-compliant design and professional inspection.
- Treating survey estimates as universal facts: Cambridge and EIA figures are dated, modeled or survey-based and describe broad populations.
- Comparing unlike tariffs: label each rate as retail, wholesale, hosted or all-in before drawing a conclusion.
What to record in a mining spreadsheet
For each machine and site, store the model, firmware mode, wall watts, hashrate, J/TH, voltage, expected uptime, pool fee, bitcoin-price assumption, network-difficulty assumption, block-subsidy assumption and calculation timestamp. Keep tariff fields for energy, demand, time-of-use, taxes, fixed charges, hosting and curtailment credits. Add cooling/PUE, repairs, labor, financing, insurance, taxes, hardware cost and planned service life.
Log actual meter kWh, pool revenue, rejected shares, temperature, downtime and repair events. Comparing the model with those records shows whether the problem is the tariff, the hardware, the cooling system or the revenue assumption. Update the model whenever the utility bill, pool terms, network conditions or machine operating mode changes.
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