Test Criteria
Often overlooked, the power supply unit (PSU) plays a crucial role in supplying the PC with stable and sufficient power. Whether you only need a 300W PSU for a modest small form factor box or a 1,200W model for a gaming juggernaut, the quality of your power supply will not only affect the system's performance, but also its longevity.
Bad power can mean early failures...and there are plenty of bad PSUs out there waiting for the unwary. This is why we felt it necessary to start testing PSUs in order for our readers to make better component decisions.
Test equipment plays an important role when evaluating power supplies though, which is why it's such a difficult job to do properly. Only with the help of highly precise measurement instruments can we document the differences between comparable models in an objective and reproducible way. Tom's Hardware performs all of these tests in professional labs, just like the ones found in PSU manufacturing facilities, where we get access to equipment from Chroma. For those new to this space, Chroma is the de facto vendor of PSU testing equipment.
When testing, we measure the following details:
- Standby power consumption at 230V
- Inrush current at 115V and 230V
- Energy efficiency at 20, 50, and 100% of the stated maximum sustained load at 115V and 230V (according to the 80 PLUS consortium's certification)
- Energy efficiency at 25W, 50W, 85W, 300W, and 500W of power draw at 115V and 230V
- Hold Up Time after losing power input at 115V and 230V
- 12V rail overload test at 110% of the specified maximum sustained load
- Short circuit test at 115V and 230V
- Measurement of the temperature difference between intake and exhaust air (maximum delta) at 115V and 230V
In addition to the above mentioned values, Tom's Hardware also takes into account the ergonomics of the PSU and its accessories. This includes features like the the length and design of the cables, cable modularity, and any useful accessories. All important technical data will be presented in a table.
