Kilowatt-Hour
A kilowatt-hour is a quantity of energy: one kilowatt of power running for one hour. The electricity bill arrives in kWh.
What a kilowatt-hour is
Watts and kilowatt-hours get confused all the time, yet the difference is simple. Watts are the speed of spending, kilowatt-hours are the volume. A 3.5 kW asic that ran for an hour used 3.5 kWh. Running a full day, 84 kWh. The meter on the wall counts the second quantity, and the rate is written per that same unit.
For mining, this is the main expense unit. An ASIC works without days off, so converting the spec sheet into a bill takes one line: kilowatts multiplied by 24 and by the days of the month. Mistakes here are expensive, because they repeat every month.
The Spanish tariff is layered: household contracts up to 15 kW have three price periods for energy and two for power, and a kilowatt-hour at night or on weekends is cheaper than on a weekday evening. A miner that runs around the clock anyway cares about the average daily price, and for quick estimates we take about 0.135 euros per kWh.
Quick reference table
| What it measures | volume of energy, not power |
| Formula | kilowatts multiplied by hours |
| S21 per day | 84 kWh |
| S21 per month | about 2520 kWh |
| Average Spanish household rate | about 0.135 €/kWh |
How to do the math in your head
Memorize one multiplier: a kilowatt of around-the-clock load is 720 kWh per month. The rest is multiplication: a 3.5 kW asic is 2520 kWh, at a rate of 0.135 that is about 340 euros. You can now size up any model in the catalog in ten seconds without a calculator.
And one honesty check on whoever sells you electricity: if you are promised a rate, look at what it covers. The price per kilowatt-hour and the charge for contracted power are separate lines on the bill, and cheap energy with expensive power can eat all the savings.
Example
Two ASICs: an S21 at 3.5 kW and a desktop miner at 0.5 kW. The first burns 84 kWh per day, the second 12. On the bill that is 340 euros a month versus 49 at the same rate. The desktop asic, though, mines orders of magnitude less, so a cheap bill does not yet mean profitable mining: put it all together in the calculator.
Related terms
Where to go next on the site
Numbers
Hardware
- Antminer S21 tool
Questions and answers
How kW differs from kWh
A kilowatt is the speed of spending, a kilowatt-hour is the volume. A 3.5 kW ASIC uses 3.5 kWh in an hour, 84 in a day.
How many kWh does an average ASIC use per month
A kilowatt of continuous load gives 720 kWh per month. Multiply the miner's rated kilowatts by 720 and you get the monthly volume.
Does a night tariff help a miner
Partly: the asic runs in the daytime too, so you pay the average daily price. The clear winners are those who switch the ASIC off during expensive hours, but downtime costs money as well, so both options need to be computed.
How the terms connect
Every link in the chain is clickable. Orange marks where you are now.
Looking for an ASIC miner
The catalog holds 212 models. You can compare them by hashrate and by joules per terahash, then plug your own rate into the calculator and see what stays in your pocket.
Page written and checked by Denys Klimchuk. Updated .