How many miners will my site take? A sizing worksheet

The most common question we get is how many machines a site can hold, and the most common answer people arrive with is wrong, because they divided their supply by the machine's rated draw and stopped there. The real figure is lower, and it is lower for four separate reasons that stack.

1. Your usable electrical capacity

Start with your incoming service in kilowatts, not amps, and subtract everything else the building uses. Then apply the continuous load rule: mining machines run at close to rated draw around the clock, so every circuit is loaded to no more than eighty percent of its breaker rating.

So a 100 kW service with 10 kW of other load gives 90 kW available, and at eighty percent that is 72 kW usable for machines. Not 100. This single step removes about a fifth of the number most people start with.

2. Distribution losses

Between the meter and the machine sit a transformer, panels and PDUs, and each stage loses a little. Budget five to eight percent of your total draw as overhead. On our 72 kW that leaves roughly 67 kW at the machines.

3. Divide by the real draw, not the rated draw

A machine rated at 3,500 W draws more than that at the wall, because the rating is often the machine and not the losses around it, and because draw rises with ambient temperature. Add a small margin. Sixty-seven kilowatts divided by 3.6 kW gives about eighteen machines, from a site that looked like it could hold twenty-eight.

If that number disappoints, the lever is efficiency rather than quantity. On a site with limited capacity the only way to more hashrate is more terahash per watt, which is why the shortlist by power price pushes efficient machines at anyone whose ceiling is kilowatts.

4. Can you get the heat out?

Every kilowatt in is a kilowatt of heat out. Eighteen machines is about 65 kilowatts of heat, continuously, and air cooled sites frequently hit the ventilation limit before the electrical one. The check is whether you have the intake and exhaust area, and the temperature rise across the room, at the warmest week of the year rather than today. Sizing method in sizing power and cooling.

5. Space, weight and access

Machines need airflow separation, not just floor area: hot exhaust must not return to the intake, which usually means a hot side and a cold side rather than rows facing each other. Add space for a person to work behind them, and check the floor loading if you are racking. A rack of hydro units is heavy before you add water.

6. Noise, which is a capacity limit too

On many small and medium sites the real ceiling is not electrical or thermal, it is how much noise the neighbours will accept. Measure the background level at the nearest occupied building at night before you fix a number, as in how loud a mining site is.

The worksheet, in order

• Incoming service in kW, minus other building load
• Multiply by 0.8 for continuous load
• Subtract five to eight percent for distribution losses
• Divide by the machine's real draw plus a margin
• Check the result against your ventilation or loop capacity
• Check it against space, floor loading and noise, and take the lowest of the six

Whichever of those six comes out smallest is your site's actual capacity. Everything above it is a plan for a different building.