Understand the fundamentals
Power is a rate; energy accumulates
Power is how fast energy is delivered or used. It is measured in watts (W). One watt is one joule per second, and a joule is a small unit of energy. A kilowatt, written kW, is 1,000 watts. Energy is the total amount used over a period of time. A load is any equipment that uses electricity, such as a miner. A kilowatt-hour, written kWh, is the energy a steady one-kilowatt load uses in one hour.
The “hour” in kWh matters. A dashboard showing 3 kW tells you a power level: how fast energy is being used. A meter showing 72 kWh tells you the total energy used over some period. You cannot compare the two numbers until you know how long that period was.
See how it works
Worked example: one miner for one day
Imagine a miner that draws a steady 3 kW for 24 hours. Energy is power multiplied by time, so 3 × 24 = 72 kWh. Now assume an energy-only price of $0.05 per kWh. The energy charge is 72 × $0.05 = $3.60. These numbers are made up for teaching. They are not a real electricity rate or a profit forecast.
If the miner runs only 12 hours at that power, its energy is 36 kWh. If power changes during the day, work out the energy for each period and add them up. Or use a reliable energy meter. For example, 3 kW for 4 hours and then 2 kW for 4 hours gives (3 × 4) + (2 × 4) = 20 kWh. Using the 3 kW peak for all 8 hours would give 24 kWh, which is too high. In the same way, multiplying one peak (highest) reading by 24 hours can make a daily total too high.
| Power | Duration | Energy |
|---|---|---|
| 3 kW | 1 hour | 3 kWh |
| 3 kW | 12 hours | 36 kWh |
| 3 kW | 24 hours | 72 kWh |
| 2 kW | 5 hours | 10 kWh |
Connect it to the field
Know what the estimate leaves out
A facility also uses electricity for cooling, networking and other equipment. Electricity bills can include more than energy. Examples are fixed fees and demand charges, which are usually based on the highest power drawn in a billing period. Mining income also depends on more than energy cost. Your part as a Miner Technician is to supply accurate equipment and operating data, not to promise a profit.
In a report, state the power (measured or assumed), how long it ran, which equipment the number covers and the price you assumed. Then someone else can repeat your math and see where the real cost may differ.
Terms used in this lesson
- Power · kW
- The rate at which energy is used.
- Energy · kWh
- The total energy used over time: power multiplied by hours. 1 kWh is a steady 1 kW for one hour.
- Efficiency · J/TH
- Energy used for each terahash of hashing work. Lower is more efficient. Compare values only under the same conditions.
Optional references & further reading
Use current manufacturer instructions for the exact equipment and your site’s approved procedures. Course levels do not grant task authorization.