While Citius, Altius, Fortius, or faster, higher, stronger is the motto for the Olympics, the PC power supply market also follows this adage fairly religiously. Manufacturers continue to leapfrog each other by enabling increasingly higher outputs to cope with the most aggressively overclocked CPUs and multi-card graphics configurations drawing hundreds of watts.
It gets bad enough that a cyber-stroll through Newegg or TigerDirect gives you the impression that power supplies under 500 or 600 W aren't even worth looking at. After all, if a fairly affordable card like the Radeon HD 7950 requires at least a 500 W PSU, according to AMD, then adding an overclocked CPU and some storage necessitates even more, right? Fortunately, even as the power supply vendors crank up output, they're simultaneously improving the efficiency of their highest-end offerings.
For this round-up of efficient desktop power supplies, we asked power supply manufacturers to send us their 80 PLUS Platinum-rated products at the lower end of the output spectrum. We set the upper limit at 600 W. Any lower and the number of contestants would have been too small. Our objective was to help system builders find an efficient solution for single-graphics card gaming and other moderately-demanding applications. Five companies submitted samples: the Antec EarthWatts Platinum 550 W, Cooler Master Silent Pro Platinum 550 W, Enermax Platimax 600 W, Kingwin Lazer Platinum 550 W, and Rosewill Fortress-550.
Naturally, the 80 PLUS Platinum rating costs more to procure. But although the output of our five test candidates only varies by 50 W, their price differences turn out to be quite a bit more significant. The list price of Antec's unit is only $120, the Enermax asks you to pay as much as $190! The Cooler Master and Kingwin power supplies are both listed at $170, while Rosewill's sells for $140. Keep in mind that we're citing each manufacturer's suggested price; the actual prices of these power supplies are often up to 20% lower.
Antec released Platinum-rated models of its EarthWatts family some time ago, and today there are three models ranging from 450 to 650 W. The EarthWatts Platinum power supplies are value-oriented and marketed to the "Casual" and "Office" segments. This is a surprising strategy from Antec; most other PSU manufacturers only stick that coveted 80 PLUS Platinum logo on premium products with higher output levels. Nevertheless, as we mentioned on the previous page, Antec achieves its rating at the lowest price point.
While the Antec power supply's packaging reflects its value-oriented product positioning, the workmanship that went into building the PSU itself is impeccable.
Unfortunately, the EarthWatts Platinum doesn't employ modular cable management, though this obviously helps maintain a low price point. Despite the lack of modularity, the cable strands are of the quality, sleeved sort. Antec provides slightly fewer connectors than competing models, but we still think that two PCIe connectors, four Molex connectors, and five SATA connectors are sufficient for a 550 W unit. You'll only really need to look elsewhere if you're planning to use more than one graphics card or a big array of storage drives. The cable lengths are typical for power supplies in this class.
Antec leans on a 120 mm fan, which is smaller than the fans used in the other PSUs we're reviewing today, though there's nothing wrong with that per se. The EarthWatts power supply is also the only one in this test sporting a four-rail design. Breaking 12 V power up into multiple rails can sometimes be less flexible than just one rail. However, each of the Antec’s four 12 V rails can supply up to 30 A of current, for a combined maximum of up to 516 W.
| Antec Earthwatts Platinum 550 W | ||||||||
|---|---|---|---|---|---|---|---|---|
| AC Input | 100-240 V, 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 |
| 16 A | 16 A | 30 A | 30 A | 30 A | 30 A | 0.3 A | 3.0 A | |
| Individual Output | 3.6 W | 15 W | ||||||
| Rail Utilization | Sys | Sys | CPU And VGA | |||||
| Combined Output | 95 W | 516 W | ||||||
| Total Continuous Output | 550 W | |||||||
| Peak Output | 605 W | |||||||
Efficiency According to the 80 PLUS Specification

Efficiency by Output Power

We tested the Antec EarthWatts Platinum 550 W’s compliance with the 80 PLUS Platinum spec by loading up mostly the +12 V rails. We were surprised to see that it barely missed the 80 PLUS Platinum efficiency spec at half and full loads, falling short of both marks by 0.7 percentage points.
However, the EarthWatts Platinum 550 W still complies with the Platinum spec, because the test method used by the 80 PLUS organization differs from ours. As explained by Antec, 80 PLUS loads the rails according to a manufacturer’s spec sheet. This causes the 3.3 V and 5 V rails to be loaded more, and the +12 V rails loaded less than in our more realistic scenario. Due to this discrepancy, we plan to shed more light on the 80 PLUS organization’s testing methodology in a future article.
With all of that said, Antec's EarthWatts Platinum 550 W is still a highly efficient PSU that easily masters all the other tests in our round-up. This unit passes the ripple and noise test with flying colors, and stays well below acceptable maximums.
A Closer Look at the PCB
Antec's EarthWatts Platinum line of power supplies are OEM versions of FSP Platinum models, though the black PCB does bear the Antec logo.
No corners are cut at the input filter. To the contrary, we counted three Y capacitors, two X capacitors, and three choke coils. When we examined the components and the PCB layout, we found a strong similarity to the FSP Aurum family. While most capacitors are made by Chemi-Con in Japan, we also found a few capacitors made by Taiwan-based CapXon, but we don’t deem this to be a quality issue. Also worth mentioning, the soldering quality on this unit is excellent.
Back in the summer of 2011, our news team saw the Enermax Platimax line unveiled at Computex, and it left an indelible impression. Enermax sent us a 600 W Platimax model for this round-up, and its packaging and workmanship are as impeccable as what we witnessed at the trade show in Taipei.
The Enermax Platimax 600 W has three 12 V rails, each of which can handle up to 25 A. Together, the three rails are rated for up to 600 W, which is the power supply's total rated output, too. We were able to draw 600 W from the three 12 V rails without any adverse effect on the other voltages.
This power supply has plenty of connectors: eight SATA, eight four-pin Molex, and four PCIe. The cables are partially modular, meaning that only the mandatory motherboard and auxiliary CPU cables are permanently attached to the unit, and cable length is above average.
| Enermax Platimax 600 W | ||||||||
|---|---|---|---|---|---|---|---|---|
| AC Input | 100-240 V, 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 | n/a | 0.5 A | 2.5 A | |
| Individual Output | 6 W | 1 W | ||||||
| Rail Utilization | Sys | Sys | CPU And VGA | |||||
| Combined Output | 100 W | 600 W | ||||||
| Total Continuous Output | 600 W | |||||||
| Peak Output | 660 W | |||||||
Efficiency According to the 80 PLUS Specification

Efficiency by Output Power

In our labs, the Platimax 600 W yields 80 PLUS measurements that are spot-on with the Platinum spec’s minimum values. At very low loads, however, efficiency begins to suffer. At a mere 25 W load, the Platimax is down to 74 percent efficiency, increasing to just 83 percent at 50 W.
At just a tad over 16 ms, the hold-up time barely exceeds the minimum stated in the ATX specification. While the other values are in compliance as well, the ripple and noise measurements warrant a closer look. On the three most important DC rails, we see voltage spikes, which are a few nanoseconds long, and exceed the allowable maximums on the 3.3 V rail. However, there can be multiple reasons for this phenomenon, and since the voltages are otherwise very clean, we’re not going to call a foul here.
A Closer Look at the PCB
A peek at the interior shows that the power supply is based on the so-called Dynamic Hybrid Transformer Topology. It is similar to LLC resonant toplogy used in expensive, high-efficiency power supplies. Since the Enermax supply is also highly efficient, it is not surprising that a similar architecture is being implemented.
The input filter design is somewhat unusual, as there are four Y capacitors, but no X capacitors. However, two X capacitors are found behind the bridge rectifier, so everything is copacetic after all. The soldering and general mechanical quality of this power supply are excellent, which comes as no surprise since Enermax uses high-quality components from Japan.
The Kingwin Lazer Platinum 550 W is listed for $170, though it often sells for less. This PSU’s surface finish is smooth compared to the other products in this round-up. While this is just an aesthetic design element, and not an indicator of quality, we mention it because we found no faults with the power supply’s manufacturing quality, either.
White fan blades offer a nice contrast to the more common black fans used in competing models. The cabling is semi-modular; the sleeved 24-pin ATX, 12 V auxiliary, and first PCIe cables aren't removable. Kingwin's modular cables are flat and unsleeved, which should help facilitate better airflow inside your enclosure.
The cable lengths and the number of connectors are better than average: four PCIe and eight SATA connectors are generous, while five four-pin Molex connectors are OK. In contrast to the Antec and Enermax supplies, Kingwin's solution sports one 12 V rail, which can be loaded up to 45.5 A. Because it's a single-rail supply, the modular cable sockets don't need to be labeled. After all, they're identically-shaped and tied into the same internal rails.
| Kingwin LZP-550 | ||||||||
|---|---|---|---|---|---|---|---|---|
| AC Input | 115-240 V, 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 | 45.5 A | n/a | n/a | n/a | 0.5 A | 2.5 A | |
| Individual Output | 6 W | 12.5 W | ||||||
| Rail Utilization | Sys | Sys | CPU And VGA | |||||
| Combined Output | 100 W | 546 W | ||||||
| Total Continuous Output | 550 W | |||||||
| Peak Output | 650 W | |||||||
Efficiency According to the 80 PLUS Specification

Efficiency by Output Power

Up until now, Enermax's Platimax was the the most efficient power supply that we've ever tested. But Kingwin Lazer's tops it. The LZP-550 suffers no weaknesses in the 80 PLUS compliance test and, at 20% load, it’s one percentage point more efficient than the Enermax model. In fact, as power draw drops, Kingwin's advantage over Enermax grows.
At 25 W, the LZP-550's efficiency is a respectable 79 percent, but at 50 W it jumps to 87 percent. This power supply also sports the highest hold-up time in the test field, at almost 30 ms. The ripple and noise values are also excellent. There is simply nothing we dislike about the Kingwin Lazer Platinum 550 W.
A Closer Look at the PCB
The LZP-550's PCB does not cover the entire floor inside the power supply’s enclosure. There is, however, a second circuit board on a side wall.
The input filter can be found on the main PCB and consists of two choke coils, four Y capacitors, and three X capacitors. This PSU does not sport a metal oxide varistor, though. In order to achieve its high efficiency, the Kingwin supply is based on a modern LLC resonant topology. While all the components are high-quality parts from Japan, in our opinion, the soldering quality leaves room for improvement.
We've seen Cooler Master launch two power supply families in the past year or so. At the end of 2011, it introduced the Silent Pro Hybrid series. This line-up of 80 PLUS Gold-rated PSUs shuts its fan off under low-load conditions where moderate ambient temperatures allow. The fan switches on when the load exceeds right around 200 W.
Cooler Master's Silent Pro Platinum family ups the ante, according to the company's spec sheet.
We received a 550 W entry-level model, and the feature list is impressive: fully sleeved permanent cables, flat modular cables, and lots of connectors, namely four PCIe, five Molex, and a whopping nine SATA connectors. However, we wish that it came with longer cables, as 27.5” may be a tad short if you want to route them behind a motherboard tray.
This power supply sports a single 12 V rail, which can be loaded with up to 45 A. It ships in a huge cardboard box, with the power supply nestled into a soft, velvet-like bag. Although it looked nice, we weren't big fans of the overpowering chemical smell the bag was emitting.
| Cooler Master Silent Pro Platinum 550 W | ||||||||
|---|---|---|---|---|---|---|---|---|
| AC Input | 100-240 V, 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 | 25 S | 45 A | n/a | n/a | n/a | 0.3 A | 3.5 A | |
| Individual Output | 32 A | 17.5 W | 10.5 W | |||||
| Rail Utilization | Sys | Sys | CPU And VGA | |||||
| Combined Output | 150 W | 540 W | ||||||
| Total Continuous Output | 550 W | |||||||
| Peak Output | n/a | |||||||
Efficiency According to the 80 PLUS Specification

Efficiency by Output Power

Cooler Master's Silent Pro Platinum 550 W not only holds its own in our lab tests, but its efficiency even tops the Kingwin Lazer, which just broke Antec's efficiency record two pages ago. At both 20 and 50 percent load, it takes a one-percent lead over the last power supply we benchmarked, achieving 92 and 93 percent efficiency, respectively.
The trend continues at very light loads. No other power supply in this round-up is able to achieve 81 percent efficiency at 25 W. The Cooler Master supply coasts through the other metrics as well, including the tricky ripple and noise test. While the picture on the scope shows slightly larger ripples than Kingwin's exemplary PSU, the Cooler Master product easily complies with the requirements.
A Closer Look at the PCB
The main PCB, colored black, is smaller than the floor area of the enclosure. There is an auxiliary board mounted to a side wall, and massive cooling fins dominate the interior.
When we examined the input filter, along with the primary and secondary side circuits, we couldn’t find any flaws or evidence of cut corners. Cooler Master sources the most important components from suppliers in Japan, using premium parts in a modern circuit topology. The soldering quality is very good here as well (almost perfect, in fact). Not surprisingly, the Silent Pro Platinum 550 W sports a 135 mm fan made by none other than Cooler Master itself.
The Rosewill Fortress 550 is listed for only $140, but is often available for less than $100, making it the least-expensive power supply in our round-up. As such, we can understand why it doesn't offer modular cabling. While all cables are sleeved and sufficiently long, there are only two PCIe connectors. Five Molex and six SATA connectors round out the cable package.
Like the Cooler Master and Kingwin supplies, Rosewill's has a single +12 V rail able to supply up to 45.5 A (exactly like the Kingwin unit). In fact, we cannot help but notice that the technical specs of Rosewill's Fortress 550 and Kingwin's Lazer Platinum 550 W are completely identical. The build quality of this power supply is likewise excellent.
| Rosewill Fortress 550 | ||||||||
|---|---|---|---|---|---|---|---|---|
| AC Input | 100-240 V, 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 | 45.5 A | n/a | n/a | n/a | 0.5 A | 2.5 A | |
| Individual Output | 6 W | 12.5 W | ||||||
| Rail Utilization | Sys | Sys | CPU And VGA | |||||
| Combined Output | 100 W | 546 W | ||||||
| Total Continuous Output | 550 W | |||||||
| Peak Output | 650 W | |||||||
Efficiency According to the 80 PLUS Specification

Efficiency by Output Power

Our test suite doesn’t expose any significant differences between the Kingwin and Rosewill products. The efficiency values for both PSUs are really close when we perform our 80 PLUS Platinum compliance tests, and the two competing power supplies rightfully bear the coveted logo.
At low load, Rosewill's Fortress pulls ahead of the Kingwin supply by being one or two percentage points more efficient. At 25 W, the Fortress 550's efficiency is two percentage points above the Lazer Platinum 550 W's at 79 percent. Perhaps the fact that this power supply has no modular cabling helps. After all, each connector ever so slightly decreases efficiency.
When we measure the hold-up time, Rosewill's Fortress 550 achieves 17 ms, which is slightly less than the average of the other supplies, but still in compliance with the 16 ms demanded by the ATX specification. Like the other power supplies in this round-up, the Fortress passes our overload test, which subjects the power supply to 110% of its nominal load.
At the end of the suite, we check ripple and noise to determine the quality of the DC output voltage, generated from an intermediate AC voltage. The oscilloscope shows that the Rosewill Fortress sports significant ripples, which could be passable as long as they stay within the ATX spec. However, we measure a maximum of 170 mV on the +12 V rail, exceeding the ATX limit of 120 mV. Unfortunately, even the 149 mV average is too high.
A Closer Look at the PCB
The Fortress 550's main PCB is smaller than the one inside Kingwin's Lazer, most likely because Rosewill doesn't employ modular cables. Although both PSUs offer identical tech specs, their PCB layouts are not the same.
First, Rosewill’s input filter is located at the mains receptacle. This small PCB sports just two X and Y capacitors each, along with a choke coil. The rest of the input filter consists of two more X and two more Y capacitors, along with an MOV seated behind the bridge rectifier. The topology is LLC, and all components are sourced from Japan. The soldering quality looks OK, but it is by no means perfect.
| Test Hardware | |
|---|---|
| AC Source | Chroma Programmable AC Source 6530 |
| Power Meter | Yokogawa WT210 Digital Power Meter |
| Loads | 4 x 600 W Chroma 63306 for 12 V testing 4 x 300 W Chroma 63303 for 5 and 3.3 V testing using Chroma HighSpeed- DC Load Mainframes 6334 |
| Oscilloscope | Tektronix DPO3034 Digital Phosphore Oscilloscope (300 MHz) |
| Test Procedure | |
| Voltages | 110 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 12/5/3.3V 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 W 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. exhaust temperature delta tracking highest delta during all tests |
Please refer to our Desktop Power Supply Charts to see more results of these and other power supplies.
Hold-Up Time and Inrush Current


For what it's worth, we were unable to get usable readings from Antec's power supply during our Inrush Current test.
Please refer to our Desktop Power Supply Charts to see more results of these and other power supplies.



Please refer to our Desktop Power Supply Charts to see more results of these and other power supplies.





If it’s the cream of the power supply crop that you seek, then we just looked at five different models that certainly deserve such a distinction. They all sport very high efficiency, which is what we were expecting from a round-up of Platinum-rated PSUs.

But two of these products stand out from the crowd: Cooler Master's Silent Pro Platinum gives us unprecedented power efficiency, followed by the value-packed Rosewill Fortress 550.
However, the Enermax Platimax 600 W and Kingwin Lazer Titanium 550 W aren't all that far behind. Most of the samples we reviewed exhibited minor flaws. For example, Rosewill's Fortress 550 exceeds the maximum allowable ripple voltage on the 12 V rail, which is an indication of cutting corners in circuit design or component quality. While Enermax's Platimax also exhibits spikes on the DC rails, they're extremely short and can safely be disregarded.
Although the Cooler Master and Kingwin models don't suffer any specific flaws, we still have suggestions for both manufacturers: we’d like to see longer cables on the Silent Pro Platinum, and better soldering on the Lazer Platinum.
At the end of the day, Cooler Master, Enermax, and Kingwin share a first-place finish in today's round-up, and prospective customers should make their decision between those three power supplies based on your own criteria (price, the number of 12 V rails, connector counts, and so on).
The price/performance winner is Antec. No other company offers such high efficiency at an entry-level price. Though the EarthWatts Platinum 550 W misses the stringent 80 PLUS Platinum thresholds by a slim margin, we think the power supply's price point offsets that to a large degree. We also determined that the 80 PLUS organization's test criteria partly differs from ours, primarily with respect to the load placed on each rail. So, we do believe that Antec deserves its Platinum logo, as long as you follow the organization's methodology. If you can live without modular cables, the EarthWatts Platinum is worth looking at, too.










































