Measure the workload you mean by always on
A mini PC can idle, process background tasks, stream media or run sustained workloads. Its average power depends on that mix. Measure cumulative kWh over several representative days, then divide energy by hours and multiply by 1,000 to find average watts. A one-minute idle reading does not describe a 24/7 month.
ENERGY STAR computer guidance emphasizes power-management features and efficient operation, but certification or a power-supply rating is not a personalized average. Record operating-system settings, attached devices and workload during the measurement so a later test can explain why the result changed.
Convert average watts into a 30-day month
For an illustrative 20 W average, 0.020 kW × 24 hours × 30 days equals 14.4 kWh. At $0.18/kWh, the month costs $2.592, rounded to $2.59. A full year using 365 days would be 175.2 kWh and $31.54 at the same rate.
If your meter reports 2.4 kWh over five complete days, the daily average is 0.48 kWh and the 30-day projection is again 14.4 kWh. Do not enter 20 W and then apply a second idle discount when that average already includes idle and active periods.
| Measured average | 30-day energy | Monthly cost at $0.18/kWh | Annual energy |
|---|---|---|---|
| 10 W | 7.2 kWh | $1.30 | 87.6 kWh |
| 20 W | 14.4 kWh | $2.59 | 175.2 kWh |
| 50 W | 36.0 kWh | $6.48 | 438.0 kWh |
Draw the equipment boundary
A monitor that sleeps most of the day, an external drive, powered USB hub, router and uninterruptible power supply may each use electricity. Measure the mini PC alone for a device figure or the complete compatible power strip for a system figure. Do not switch between those boundaries in the comparison.
If the mini PC replaces a NAS or larger desktop, compare equivalent storage, availability and workload. A lower nameplate rating does not prove the same job is being performed.
Use scheduling where the service allows it
List the hours when the machine must actually be available. If a server task can run on a schedule, supported sleep, shutdown or wake features may reduce idle time. Test reliability and remeasure energy after the change instead of assigning a generic percentage saving.
Keep software updated and use manufacturer-supported power settings. Do not interrupt storage operations or remote access requirements merely to reach the lowest cost scenario. A useful estimate balances the required service with clearly measured electricity.
Choose your next step
Continue with the question that matches your next decision:
Sources & further reading
Numerical examples are illustrative unless explicitly described as measured. This guide does not claim hands-on product testing. Read the methodology and editorial disclosure.