Mining Electrical Load Calculation: A Worked Guide

Before a single miner plugs in, the question that decides whether a setup is safe is simple: does the electrical service have the capacity to carry the load? A mining electrical load calculation answers that by summing every miner’s continuous draw, applying the continuous-load derating, and comparing the total against the panel and service rating. Get it right and the breakers hold and the wiring stays cool; get it wrong and you overload the panel, trip the main, or worse. This guide works through the full calculation, from one miner to a panel full of them, with the math shown. The actual panel, feeders, and any service upgrade are work for a licensed electrician to local code; this is operator-level planning so you arrive at that electrician with real numbers.

The load calculation in four steps

The calculation scales the same way whether for one miner or fifty.

Step 1 — total connected load. Add the wattage of every miner plus supporting equipment (PDUs draw little, but fans, pumps, dehumidifiers, and lighting count). Use manufacturer wattage figures, not guesses.

Step 2 — convert to current. Divide total watts by the circuit voltage. For 240V loads, current = watts ÷ 240.

Step 3 — apply the 80% continuous rule. Mining is a continuous load, so the service and circuits must be loaded to no more than 80 percent of their rating. Divide the continuous current by 0.8 (the same as multiplying by 1.25) to get the minimum rating required.

Step 4 — compare against capacity. Check that figure against the panel’s rating and the available capacity after existing household loads. If it exceeds available capacity, you need more circuits, a sub-panel, or a service upgrade.

The 80 percent rule is the same constraint that governs individual breakers, covered in the circuit breaker selection guide. The load calculation applies it at the panel and service level rather than the single-circuit level.

A worked example: four miners at home

Take four air-cooled miners drawing about 3,500 W each on 240V. (Use the spec-sheet wattage for your actual units; these figures illustrate an S21-class unit.)

Step 1 — total connected load. 4 × 3,500 W = 14,000 W. Add, say, 500 W of fans and lighting: 14,500 W total.

Step 2 — current. 14,500 W ÷ 240 V = 60.4 amps continuous.

Step 3 — 80% rule. 60.4 A ÷ 0.8 = 75.5 A. The service feeding this load must support at least 75.5 A of continuous capacity for the mining load alone.

Step 4 — compare. A common residential service is 100 A or 200 A. A 100 A service already carrying the household (HVAC, water heater, kitchen, etc.) often cannot spare 75 A continuous; the mining load alone would consume most of it. A 200 A service has more room, but the existing household load still has to be subtracted first.

This is the moment many home setups discover they need a service upgrade or a dedicated sub-panel. Four flagship miners is a substantial commercial-scale load dropped into a residential service, and the calculation makes that concrete before anything trips. Adding capacity is covered in the sub-panel installation guide.

Subtracting the existing household load

The mistake that trips mains is treating the panel as empty. A home’s existing loads, air conditioning, heating, water heater, oven, everyday circuits, already consume part of the service capacity, and the mining load stacks on top.

A proper load calculation accounts for the existing demand. Electricians use a standard method that totals the dwelling’s loads with code-defined demand factors, then adds the new continuous mining load at 125 percent. The headline point for an operator: the question is never “is my service rated above my miners’ draw,” it is “is the service rated above my miners’ draw plus everything else the house runs.” On a 200 A service where the household already pulls a peak of, say, 80 A, only the remaining headroom, minus a safety margin, is available for mining, and the 80 percent continuous rule applies to that mining portion.

This existing-load accounting is precisely why the load calculation belongs to a licensed electrician for the final sign-off: they assess the real household demand and the service rating together. The operator’s job is to bring an accurate mining-load number to that conversation.

Balancing the load across circuits and phases

Total capacity is one constraint; distribution is another. Even with enough total service, the load has to be spread sensibly across circuits and, in larger setups, across phases.

Per-circuit limits

Each circuit carries only its share. Using the single-miner example, a 14.6 A miner on a 20 A circuit leaves little headroom, so it gets a dedicated circuit. Stacking miners onto a circuit requires sizing that circuit’s breaker and wire to the combined load, again at 80 percent. Mapping each miner to its circuit, the documentation covered in the cable management guide, is what makes per-circuit balancing verifiable rather than guessed.

Phase balancing

In a multi-circuit residential panel, distributing miners so each leg of the panel carries a similar load prevents one leg from overloading while the other sits idle. In a three-phase farm, balancing across the three phases is essential; an unbalanced three-phase load wastes capacity and can overheat one phase. Three-phase distribution has its own sizing, covered in the three-phase power guide, but the balancing principle is the same: spread the load evenly so no single conductor carries more than its share.

Where the load number comes from

Every figure in the calculation traces back to the miner’s rated power, so that number must be accurate. Two cautions:

• Use the manufacturer spec sheet, not the nameplate maximum or a rumor. Bitmain, Canaan, and other makers publish rated power; that is the figure to total. An undervolted or overclocked unit draws differently, so if you tune the units, base the calculation on the tuned draw, verified with a meter.
• Account for inrush and real-world variance. Miners draw a brief surge at startup and their steady draw varies with temperature and tuning. Measuring actual draw with a power meter after install, per the power meter and monitoring guide, confirms the calculation matched reality.

Because the entire calculation scales linearly off the input wattage, a 10 percent error in the assumed per-unit draw becomes a 10 percent error in the service requirement, which can be the difference between fitting and overloading. Coin Web Mining is an independent reseller and lists rated power per model so the calculation starts from real spec figures rather than estimates.

When the calculation says you need more capacity

The load calculation frequently delivers unwelcome news: the existing service cannot carry the planned fleet. That answer is valuable, because finding out before ordering hardware is far cheaper than after. The options, in rough order of cost, are these.

Add dedicated circuits within existing capacity. If the service has headroom but the panel lacks free breaker slots or circuits, an electrician can add circuits. This works when the total service rating is sufficient and only the branch-circuit distribution is the constraint.

Install a sub-panel. When the main panel is physically full but the service still has capacity, a sub-panel fed from the main adds breaker positions and a clean place to group the mining circuits. The sub-panel installation guide covers when this is the right move and how the feeder is sized.

Upgrade the service. When the calculation exceeds the service rating itself, the utility service has to grow, from 100 A to 200 A, or to a larger commercial service. This is the most expensive and involved path, requiring utility coordination, and it can take time, so it belongs in the plan before hardware is on order.

Reduce or relocate the load. Sometimes the right answer is fewer units, more efficient units that hash more per watt, or hosting some hardware off-site where the power already exists. The hosted facility evaluation guide covers when hosting beats building out home capacity. Choosing efficient units also stretches a fixed service further, since the same amperage supports more hashrate.

Each path has a cost and a lead time, and the load calculation is what tells you which one the plan requires. Running it first turns a potential stranded-hardware disaster into a known line item.

Demand factors, diversity, and why miners are different

Standard residential load calculations apply demand factors, reductions that account for the fact that not every appliance runs at once. A home rarely runs the oven, dryer, air conditioner, and every circuit simultaneously, so code lets the calculation assume some diversity and not size the service to the impossible sum of every nameplate.

Mining loads break that assumption. A miner runs at essentially full draw continuously, with no diversity, so the usual demand-factor reductions do not apply to it. The mining portion of the load is added at full value, at 125 percent for the continuous derating, on top of the diversified household load. This is the single most important conceptual difference between sizing for a house and sizing for a house plus miners: the miners are a flat, full, around-the-clock load with none of the on-off diversity the rest of the home enjoys.

This is also why a service that comfortably runs a large home can be overwhelmed by a modest-looking mining addition. The home’s nameplate loads are diversified down by demand factors; the miners are not diversified at all. An electrician applying the proper method will treat the mining load as continuous and non-diversified, which is exactly why the operator’s accurate, full-draw mining number is the input that makes their calculation correct. Understating the mining load, or assuming it gets the same diversity discount as appliances, is how a service ends up overloaded despite a calculation that appeared to fit.

Running the calculation for your setup

The procedure, condensed:

• Total the rated wattage of every miner and supporting device.
• Divide by voltage to get continuous current.
• Divide by 0.8 (×1.25) for the minimum capacity the mining load requires.
• Subtract existing household demand from the service rating to find available headroom.
• Confirm the mining requirement fits within that headroom; if not, plan a sub-panel or service upgrade.
• Balance the load across circuits and phases so no conductor exceeds its share.
• Verify with a meter after install and have a licensed electrician sign off on the panel, feeders, and any upgrade.

Run this before buying hardware, not after. The most expensive mistake in home mining is ordering several units, then discovering the service cannot carry them and facing a costly upgrade or stranded equipment. The math takes ten minutes and tells you exactly how much electrical work the plan requires. The panel and service decisions that follow are the electrician’s; the load number that drives them is yours to get right.

References

• Electricity use in homes — U.S. Energy Information Administration
• Antminer rated power specifications — Bitmain
• Avalon miner rated power specifications — Canaan

Run the numbers before you order. The Coin Web Mining shop lists rated power for every model so your load calculation starts from real figures, and we can quote multi-unit orders once you know what your service will carry.