500W to 550W: 12 Power Supplies Compared

Thoughts and Recommendations

So there you have it, another 12 power supplies reviewed and dissected. This time, our conclusion is a little easier because there are only a few models that really stuck out from the crowd. There are a few areas where companies try to differentiate, and which areas you think are most important will influence our recommendation.

First we have acoustic noise, which can be critical if you want to build a "silent" computer. Next we have efficiency, which is often overhyped considering a 1% or even 2% difference doesn't really equal a lot of money over the course of the year. Still, all things being equal, higher efficiency is desirable. Cooling performance is also important, and is often directly related to the efficiency -- although the components also play a large role. Some are also interested in the features of the power supply (i.e. cable lengths, cable management, accessories, etc.) Finally, we have voltage stability and quality, which is arguably the most important aspect -- especially if you plan on overclocking your system.

Below we've listed the various areas you might focus on, along with PSU recommendations that do particularly well in that category.

Cable Lengths and Connectors

There were a lot of differences between most of the power supplies, as we've already discussed. The Arctic Cooling PSU is the only unit that doesn't include an 8-pin ATX connector. We talked with the company about this, and they insisted 8-pin connectors aren't necessary -- you can just use a 4-pin connector in half of an 8-pin jack on your motherboard. While it may work, we would still prefer to have an 8-pin connector; if it's unnecessary, why do motherboards have eight pin jacks?

The ATX cable lengths on the Arctic Cooling Fusion, Akasa Green Power, BFG LS-550, and OCZ ModXStream Pro are rather short at just 40 cm, which would definitely be a problem in larger cases or bottom mounted PSU designs. The Tagan SuperRock has the longest ATX cables at 55 cm. The remaining power supplies are 50 cm, which is the "standard" length.

The good news is that all of the tested power supplies have at least two PEG connectors, which is enough to run either a lower-end SLI/CF setup or a single high-end graphics cards with two PEG jacks. Arctic Cooling is the only unit that provides four PCI-E connectors. Cable lengths are also quite different; if you need longer cables, we recommend the Tagan SuperRock, Seasonic S12II or M12II, or the BFG LS-550.

We already discussed the relative importance of SATA and Molex connectors. A typical PC might only need one of each, and even high-end PCs might only need four or five of each connector type. We wanted to fully populate the drive bays in computer cases that we test, so we had PC Power & Cooling build us a custom Turbo Cool 860 with 15 SATA connectors, but most people don't need that kind of setup. If you do want more connectors, out of the tested power supplies we recommend the Tagan units. Both include eight SATA connectors and six Molex connectors, with very good cable lengths. Arctic Cooling provide six SATA connectors, but they are on a single harness which could prove problematic in certain cases.

DC Voltage Regulation and Quality

All of the power supplies stayed within specifications, which is very good to see. Since these are mostly high-end units, we didn't expect anything less, but kudos regardless. Many of the power supplies stayed within 3% regulation, which is what most companies aim for. Ideally, voltages should start about 1% above the nominal value and stay in that range. Most 3.3V and 5V rails ended up dropping about 3% below regulation, but ripple and noise was generally good.

A few of the units come pretty close to the maximum and minimum allowed voltages on the various rails, for example the Sunbeam. Ripple also exceeded specifications by a few millivolts on the Sunbeam. Overall, the 12V rail is the most important rail, and the BFG LS-550 manages an impressive 1.5% regulation on this rail. Seasonic also scores some points here with the tightest regulation we have seen to date.

Efficiency

A quick look at the efficiency chart shows there's only one power supply that provides superior efficiency at all voltage inputs, and that's the BFG LS-550. With 120VAC it starts at 82% efficiency and reaches a maximum of 86% efficiency; 230VAC performed even better, with 86% efficiency at 20/80 loads and a maximum of 88% efficiency at 50% load. The Arctic Cooling Fusion also performs well, reaching 88% efficiency at a medium load. The Cooler Master Silent Pro does well on 230VAC, but it has minor flaws on 120VAC.

All of the other units manage to reach 85% efficiency (230VAC), which is pretty typical these days. Considering the performance of the BFG, which is manufactured by Enhance, we expected similar performance from Tagan; unfortunately, that's not the case. We would like to see Tagan work on refining their unit to match the performance of BFG.

Acoustic Noise

Acoustic noise is often an important consideration, and many people want their computers to be seen and not heard. Our equipment can measure down to 17 dB(A), at which point background noise comes into play. Noise levels at medium load and lower are typically the important consideration, since few users actually run their power supplies at more than 50% load. Our charts show that most of the power supplies are able to remain very quiet below 50% load, to the point where other components in the computer will almost certainly generate more noise.

The Arctic Cooling Fusion again warrants a mention, with 17 to 18 dB up to 50% load. The Cooler Master Silent Pro performs superbly, along with the Tagan SuperRock, and both remain below 20 dB. Akasa, Corsair, and Enermax also perform well. Seasonic and Sunbeam prefer to take the safe route and spin the fans faster in order to keep temperatures down, which is often the better course of action if you prefer longevity overload noise.

Cooling Performance

Not surprisingly, the crown for the best cooling performance goes to Seasonic. This goes hand-in-hand with their higher noise levels, which helps to keep temperatures in check. Seasonic also built the Arctic Cooling Fusion, which delivers very good results. Our temperature chart looked at Delta K, the difference between internal and exhaust temperatures. The only three power supplies to generate negative scores are built by Seasonic. Akasa, BFG, and Corsair don't quite match the Seasonic built units, but performance is very good in all three cases.

Unfortunately, the Sunbeam Tuniq Prophecy didn't survive our burn-in test. It self-destructed under full load at 40°C, so we definitely wouldn't recommend that power supply unless you live in a cold environment or only plan to run at lower loads. All of the other units survived heat conditions of 50°C.

Prices

Last, we come to prices, which for some people is far and away most important factor in choosing a power supply. Not all of the units are available in all locations, so you will also have to take that into consideration. The BFG LS-550 is only available in the US right now, but we've seen other BFG power supplies in Europe so we have high hopes it will soon be there as well. For the overall performance it delivers, the BFG is an excellent bargain at $70. The Arctic Cooling Fusion is available for €55 or $64, and at that price it's a great bargain. The Tagan SuperRock also perform very good, and a price of €64 makes it our third choice for overall value and performance.

On the opposite end of the scale, the Enermax Liberty Eco is simply too expensive right now. The Cooler Master Silent Pro could also do with a slight price drop. Seasonic makes good power supplies, but they also make power supplies for a lot of competitors. As such, they tend to charge more for their own brand in order to avoid competing with their clients on similar products.