Power-on hours is one of the first numbers people look at on a used drive, and one of the easiest to over-weight. It records how long the drive has been running. It says nothing about whether it is running well.
What hours do and do not indicate
A drive with high hours in a climate-controlled server that was never power cycled may be in better condition than a low-hour drive from a machine that was repeatedly cut off at the wall. Hours describe exposure; defect counters describe damage.
Read hours alongside three other values
- Power cycle count — start/stop history, the context hours omit.
- Reallocated sector count — sectors already retired.
- Current pending sector count — unreadable sectors awaiting remap.
For solid state drives, add the wear indicator and total bytes written, which track consumed endurance more directly than elapsed time.
Setting your own bands
Most resellers define hour bands per drive class and publish them as part of a grading policy, rather than adopting a single industry number. Choose bands that reflect your buyers and your warranty exposure, then apply them consistently — the value of a band is its consistency, not its precision.
Reading hours across a batch
- Boot the ITAD Tools iPXE toolkit on each machine.
- Select Drive Health Check.
- Record power-on hours and power cycle count against the drive serial.
Results submitted with an organisation key are retained per serial, so hours can be compared across a batch instead of read one machine at a time.
Run the free bootable Drive Health Check
The ITAD Tools iPXE toolkit reads SMART data read-only, with no installed operating system and nothing to install on the machine.
Frequently asked questions
What are power-on hours?
A running total, kept by the drive, of the time it has spent powered on. It measures exposure, not condition.
How many power-on hours is too many?
There is no universal cutoff. Buyers commonly set their own bands by drive class and use case, and read hours together with defect attributes rather than on their own.
Why does power cycle count matter?
Two drives with similar hours can have very different start/stop histories. Power cycle count adds the wear context hours omit.
Do power-on hours matter for SSDs?
Less than for spinning disks. For SSDs the wear indicator and total bytes written describe consumed life more directly.
Can power-on hours be reset?
They are maintained by the drive's own firmware and are not user-resettable. The Drive Health Check reads them read-only.