Editor's Note: If you want more background on how power supply testing plays out here at Tom's Hardware, I recommend that you check out Soon At Tom's Hardware: Full-Scale Power Supply Testing before reading this piece.
Special attention gets paid to the power supply unit (PSU) these days, primarily in the high-performance and gaming community. No wonder, as the requirements of top-shelf PCs with multiple processors and modern 3D graphics cards are constantly increasing. Such computers will suck 800 W or more from the power supply under load, and for short periods that number can be substantially higher.
On the other hand, power supplies are often forgotten in offices and for everyday multimedia applications. Truth be told, compact and mid-range PCs don't require a high-performance power supply. However, investing in a high-quality power supply can pay off in several ways.
First, a good PSU guarantees a reliable and consistent supply of power to all components. This can help extend component longevity. Second, a highly energy efficient PSU helps reduce the energy consumption of a home or office. Additionally, other aspects, such as ergonomics, cable modularity, and cable length can simplify or complicate PC assembly. PSUs with good build quality also prevent nicked fingers or a less-than-optimal fit during installation. Trust us. We've seen it all.
We gathered a few mid-range models for this roundup. A top street price of $150 was our only prerequisite, and we settled on four 500 W models from Cooler Master, Enermax, FSP, and SilverStone. The coveted 80 PLUS logo is emblazoned on each box, except for SilverStone's.
Perhaps best known as a manufacturer of enthusiast-class computer cases, Cooler Master has played an important role on the PSU market for several years. The Silent Pro M500 we received for this roundup has been available in stores for several weeks, but that's no reason not to take a closer look at this power supply, especially considering its 80 PLUS certification.
As soon as you unpack the PSU, it becomes clear that the "Silent" added to the product name is not idle boasting. Silicon-covered mounting frames are included to stop vibrations from transferring to the computer case. This is a simple but effective tactic. In general, the housing of the Cooler Master Silent Pro M500 is very well made. No sharp edges or imperfect fit ruin the impression. A large 135 mm fan covers the entire base of the power supply.
The cables are flat in order to provide improved airflow inside the case, and while the lengths are sufficient, you might need some luck (Ed.: alternatively, you could do some research on component placement) to reach everything in large chassis. The ATX (20 + 4 pins) and CPU (4 + 4 pins) cables are firmly attached to the PSU, but all other cables are modular. You get plenty of cables as well: two PCIe, six SATA, and five four-pin Molex connectors.
| Cooler Master Silent Pro M500 | ||||||||
|---|---|---|---|---|---|---|---|---|
| AC Input | 100-240V, 50-60 Hz | |||||||
| DC Output | +3.3 V | +5 V | +12 V (#1) | +12 V (#2) | +12 V (#3) | +12 V (#4) | -12 V | +5 Vsb |
| 20 A | 20 A | 34 A | 0.5 A | 2.5 A | ||||
| Individual Output | 6 W | 12.5 W | ||||||
| Rail Utilization | Sys | Sys | CPU & VGA | |||||
| Combined Output | 145 W | 408 W | ||||||
| Total Continuous Output | 500 W | |||||||
| Peak Output | 620 W | |||||||
Efficiency in accordance with the 80 PLUS specification:


Efficiency under different load profiles:


We had no issues while measuring the Cooler Master Silent Pro M500. The PSU meets 80 PLUS certification requirements with some margin. In fact, it comes quite close to qualifying for the Bronze logo. Efficiency only takes a small hit under full load at 115 volts; 81% is still okay. At the other end of the scale, at 25 W and 50 W, the Cooler Master PSU performs handsomely. At 50 W, it still achieves an efficiency of nearly 82% and falls only slightly under a 25 W load to 74 percent. The long hold-up times of 18 ms at 230 V and 19.2 ms at 115 V are also noteworthy.
The Cooler Master Silent Pro M500 is above average thanks to its efficiency at low loads, and its silicone-dampened housing make it especially suitable for use in compact computers in the office or living room. Additionally, the Cooler Master Silent Pro M500 is a reliable component, with good performance ratings for multimedia systems. Heavy users should consider that Cooler Master only provides one 12 V rail, though.
As the only PSU in the roundup with an 80 PLUS Gold certification, the Enermax Pro87+ makes an immediate impression. One must search long and hard to find a PSU with such outstanding energy efficiency in the sub-$150 range, although we found that this product isn't currently available in all markets.
The Enermax Pro87+ is also a visual treat. Enermax chose to go with a gold-colored theme on both the packaging and the PSU itself. Even the fan blades have an aureate sheen.
Speaking of the fan, a nifty feature of the Enermax Pro87+ is that the fan continues to spin for 30 to 60 seconds even after the computer is shut down. This is supposed to increase the lifespan of sensitive components by evacuating residual heat from the computer case. We also like the Cord-Guard safety device that prevents you (or more likely your pet/kid/mother) from accidentally disconnecting the power cord. This is simple, but reliable.
The Enermax Pro87+ deliberately refrains from any sort of cable management or modularity. Thanks to the included Velcro cable ties, at least any unused cables can be tied up a bit so they don't impede air flow as much. Users who value the modular cable concept must resort to the Modu87+ series instead.
At least the cable length here is generous. The number of connectors is standard. In addition to the 24-pin ATX power supply and CPU connectors, you get two PCIe, six SATA, and five four-pin Molex connectors.
| Enermax PRO87+ | ||||||||
|---|---|---|---|---|---|---|---|---|
| AC Input | 100-240V, 50-60 Hz | |||||||
| DC Output | +3.3 V | +5 V | +12 V (#1) | +12 V (#2) | +12 V (#3) | +12 V (#4) | -12 V | +5 Vsb |
| 20 A | 20 A | 25 A | 25 A | 25 A | 0.5 A | 3 A | ||
| Individual Output | 5W | 15W | ||||||
| Rail Utilization | Sys | Sys | CPU & VGA | |||||
| Combined Output | 100 W | 492 W | ||||||
| Total Continuous Output | 500 W | |||||||
| Peak Output | 550 W | |||||||
Efficiency in accordance with the 80 PLUS specification:


Efficiency under different load profiles:


It becomes clear during testing that Enermax has earned its 80 PLUS Gold certification. We saw impressive results in the 87% to 91% range in our energy efficiency measurements, both at 115 as well as 230 volts. This very solid showing was confirmed in other load measurements, with efficiency falling somewhat only at very low power loads. The overload test shows that Enermax's Pro87+ still has plenty of reserves. Even with an overload of more than 20% of the power supply's stated output, it still provides stable voltages. A small weakness was revealed when testing the hold-up time, though. Here, the power supply even falls short of the ATX specification requirements. This is an unnecessary drawback given the otherwise very high quality.
In the sub-$150 price class, the Enermax Pro87+ is a genuine highlight. The high energy efficiency under mid- and full-power loads qualifies the power supply for use in rather high-end PC systems. The Enermax Pro87+ is less suitable only for very low-power computers, as the energy efficiency diminishes under very light loads. However, for such PCs, this PSU would be overkill, anyway.
The FSP Everest 85Plus 500 stands out immediately, due to its blue color. No other special features are noticeable at first glance, though. Instead, the blue PSU convinces through its internal qualities. This is hinted at by the packaging's 80 PLUS Bronze logo.
FSP plays it safe with the number of cables and connections. The ATX and CPU cables are hardwired, but all other cables—two PCIe, six SATA, and five four-pin Molex—are modular. The FSP power supply even comes with two floppy connectors, which surprised us.
You can't go wrong with the FSP Everest 85Plus 500 W power supply. Both in efficiency and equipment, Everest fares well, although it doesn't particularly excel in any way, either, as our results on the following page will show.
| FSP Everest 85Plus 500 | ||||||||
|---|---|---|---|---|---|---|---|---|
| AC Input | 100-240V, 50-60 Hz | |||||||
| DC Output | +3.3 V | +5 V | +12 V (#1) | +12 V (#2) | +12 V (#3) | +12 V (#4) | -12 V | +5 Vsb |
| 30 A | 30 A | 18 A | 18 A | 18 A | 18 A | 0.8 A | 3 A | |
| Individual Output | 9.6 W | 15 W | ||||||
| Rail Utilization | Sys | Sys | CPU & VGA | |||||
| Combined Output | 140 W | 456 W | ||||||
| Total Continuous Output | 500 W | |||||||
| Peak Output | 550 W | |||||||
Efficiency in accordance with the 80 PLUS specification:


Efficiency under different load profiles:


Our test measurements confirm the 80 PLUS certification. At 230 V, the energy efficiency values of 86% to 88% under loads of 20, 50, and 100 percent of FSP's maximum rated power are very good. The results are a bit weaker at 115 V, as expected, but still in order. The respectable efficiency values maintain over almost the entire load distribution curve, except under very low loads where efficiency falls.
At 25 W load, only 70% power efficiency is achieved, but all in all, the results are still compelling. The FSP Everest's other tests were also good. Because the FSP Everest has four 12 V rails, power can be optimally distributed over the individual rails, preventing excessively strong amperages that are more difficult to keep stable (and safe for that matter).
The SilverStone Strider SST-ST50F-230 is the only power supply in this roundup without an 80 PLUS certification logo. Instead, the packaging says that the PSU can achieve an energy efficiency "of up to 80 percent." However, the Strider is very attractively priced at around $65—and the product's aesthetics match its price.
Of course, boring looks are usually irrelevant when it comes to power supplies. More decisive is the fact that this power supply is designed for 230 V operation-only (making it useless in North America; rather, this one is for our international audience). An 80 PLUS certification is not possible under these circumstances, as the tests mandate 115 V compatibility.
Despite the low price, SilverStone didn't skimp on cable management. All cables, even the ATX and CPU, are modular and round. The number of connections is satisfactory, too: two PCIe, six SATA, and six four-pin Molex connectors.
| SilverStone Strider 500 W Evolution SST-ST50F-230 | ||||||||
|---|---|---|---|---|---|---|---|---|
| AC Input | 200-240V, 50-60 Hz | |||||||
| DC Output | +3.3 V | +5 V | +12 V (#1) | +12 V (#2) | +12 V (#3) | +12 V (#4) | -12 V | +5 Vsb |
| 25 A | 30 A | 18 A | 18 A | n/a | n/a | 0.8 A | 2.5 A | |
| Individual Output | 32 A | n/a | n/a | 9.6 W | 12.5 W | |||
| Rail Utilization | Sys | Sys | CPU & VGA | |||||
| Combined Output | 150 W | 384 W | ||||||
| Total Continuous Output | 500 W | |||||||
| Peak Output | n/a | |||||||
Efficiency in accordance with the 80 PLUS specification:

Efficiency under different load profiles:

As expected, the SilverStone Strider didn't quite keep up with the 80 PLUS-certified products in these tests. The power supply completed the relevant measurements with energy efficiency values of at least 80% and maintained this number down to the comparatively low load of 85 W. When the load dropped further, efficiency nose-dived. At 25 W, the power supply only managed a weak 62 percent. The SilverStone Strider completed the tests to verify the inrush current, the behavior at overload, short circuit, and power outages without abnormalities.
The Strider is an unspectacular, but reliable power supply at a very reasonable price. It's suitable for budget-conscious PC users who are not dependent on 115 V support or particularly concerned about efficiency under low loads.
| Test Hardware | |
|---|---|
| AC Source | Chroma Programmable AC Source 6530 |
| Power Meter | Yokogawa WT210 Digital Power Meter |
| Loads | 4 x 600W Chroma 63306 for 12 V testing |
| 4 x 300W Chroma 63303 for 5 V and 3.3 V testing | |
| using Chroma HighSpeed - DC Load Mainframes 6334 | |
| Oscilloscope | Tektronix DPO3034 Digital Phosphore Oscilloscope (300 MHz) |
| Test Procedure | |
| Voltages | 110 V and 230 V |
| Standby Power | 0.25 A fixed current to simulate PC standby power on 5 Vsb |
| 80 PLUS Efficiency Testing | 100/50/20% load, relative to specified total output Load distribution across 12/5/3.3 V rails at the same proportion as specified for 100% testing at 110 V according to ATX 2.3 specification |
| Efficiency at Fixed Loads | 25, 50, 85, 300, 500 watt loads Load distribution across 12/5/3.3 V rails at the same proportion as specified for 100% |
| Peak Load Test | 110% Overload Testing at maximum combined 12 V |
| Temperature Test | Air intake vs. outtake temperature delta tracking highest delta during all tests |
Hold-Up Time, Inrush Current, Peak, and Short Circuit Tests:




Efficiency according to the 80 PLUS specification:


Standby and temperature measurements:







The most important conclusion of this comparison test is that one does not have to spend more than $150 on a very good mid-range power supply. All tested models convinced us with high electrical quality and staying true to their 80 PLUS performance levels. But despite all power supplies achieving their advertised 500W and more, they showed individual strengths and weaknesses, making them more or less suitable for certain targeted applications.
Enermax Pro87+
In this roundup, the Enermax Pro87+ clearly and confidently takes home a test victory. With this PSU, everything is just right. The high build quality, excellent electrical quality, and equipment satisfy. In view of the 80 PLUS Gold certification, the price of around $140 isn't unreasonable, but it may still be too expensive for many users.
Cooler Master Silent Pro M500
The Cooler Master Silent Pro M500 is conspicuously inconspicuous. Thanks to very good efficiency at low loads, flat cables, and the silicon dampening frames, we recommend the Cooler Master especially for compact PC systems optimized for low power and low noise. Despite being a good fit for low-demand machines, the Cooler Master has enough reserves even to supply reliable power in high-performance multimedia systems.
FSP Everest 85Plus 500
The FSP Everest 85Plus 500 power supply is hot on Cooler Master's heels, but it doesn't quite manage the same high and flat efficiency curve. Furthermore, Cooler Master has more ideas on noise management and higher build quality. The gap between FSP and Cooler Master, however, is narrow.
SilverStone Strider SST-ST50F-230
For those who look primarily at price (and live overseas), both the FSP Everest as well as the SilverStone Strider SST-ST50F-230 are interesting. The latter power supply operates with good efficiency and has no weaknesses and a very clear price/performance focus. It's a shame it isn't usable in North America.










