Introduction

Many of you have been waiting for us to review more low-wattage power supplies. We have written about power consumption several times in the past, and we have made it clear to AnandTech readers that in most cases there is no need for a high output power supply when 400W to 500W units will do just fine. We picked a collection of such units from high-end manufacturers throughout the market, and in fact we received so many power supplies that we had to split the roundup into two parts. The first part will contain power supplies rated at 300W to 450W while the second part will focus on 500W to 550W units.

Nowadays it is very hard to find high performing units with low wattages, since manufacturers mostly aim for bigger units where they can make more money. In most cases, the high manufacturing costs of smaller units with better technology stands in the way. Nobody wants to pay $100 for a 400W power supply; there is simply no market for these units, which is why most of what we see in this field is cheap units with very poor performance to say the least. However, there are still manufacturers out there producing low-wattage units for the enthusiast market; Seasonic for example makes 300W units for OEMs as well as selling them under their own retail name.

Another issue with low-end power supplies is that they normally come with a poor selection of connectors that only lets them operate simple systems, even though they could power a decent midrange graphics card. The units we will be reviewing today are from higher-end manufacturers and some even come with a 6-pin PEG connector. Two units even come with two 6-pin connectors, which is very nice to see. The market is changing and even vendors that had 500W as the lowest wattage options in their repertoire now offer smaller units. For example, we introduced the Thermaltake TR2 QFan series recently, which starts at 300W. We will include the 400W TR2 unit today, which performs quite well.

We will also have a few world premiers today. Cooler Master sent their new Real Power Pro power supplies rated at 360W and 400W. Enermax also sent a new version of their older Liberty series, this time called Liberty Eco. Silverpower, which is not much known in the U.S., has a new OEM power supply from Seasonic that will also be in today's roundup. Silverpower is actually a spin-off from Maxpoint's Tagan brand, since customers wanted something less expensive than the usual Tagan offerings. Finally, we will have a few OEM units from various manufacturers today that we can compare with their retail brothers.

Antec Earthwatts 430W

The Antec Earthwatts 430W comes in plain grey and is equipped with an 80mm fan at the back of the power supply. Even though this power supply is an older model, we felt that we should include it again in our roundup because it is still available and is generally well regarded. The label provides the typical information we find on power supplies, with the expected figures for a 430W maximum output. Two 12V rails of 17A each are enough for most users, and the combined 12V power of 360W is quite acceptable. 360W combined equates to 15A for rail when both are "fully" loaded. We would be hesitant to try to use this PSU with one of the top-end graphics cards, but if you're using a power supply with a single 6-pin PCI-E connector you should be fine.

The inside looks familiar to other Seasonic-made power supplies, since Seasonic rarely changes their basic internal design. Of course, that doesn't mean the power supplies themselves are actually the same. There are several differences, and we expect this unit will be at a slight disadvantage. Antec uses an 80mm exhaust fan located at the rear of the power supply, but the heatsink design would normally use a 120mm intake fan. We expect this unit to be slightly warmer and/or noisier than similar designs that use a single 120mm fan. Nippon Chemi-Con manufactures the primary capacitor.

Other than the main 24-pin ATX power cable, the cable harnesses are sleeveless. Antec has taken a very simple approach in terms of appearance, and the only concession to keeping the cables tidy is the use of cable ties spaced over the length of the cables. The length of the harnesses is average, with the last Molex connector just 80cm from the power supply. The main connectors are all on 50cm cables. The quantity of connectors could have been better, but a normal midrange PC shouldn't require more than what Antec provides. There is only one 6-pin PEG connector, which makes sense considering the overall wattage and target market.

Antec Earthwatts 430W - Performance

Below are the standard DC output graphs and noise/ripple charts that we normally provide. Due to the number of power supplies included in this roundup, we will refrain from providing detailed analysis on each power supply, but will instead summarize things in the conclusion of this article. (At 8500 words and 44 pages, we figure we already have plenty of content.) However, we do recognize that these charts are important aspects of any power supply review.

Note that we are including some older, previously tested power supplies in this roundup for reference. We did not perform noise/ripple testing on all of the PSUs, so the noise/ripple charts are missing in a couple instances. We apologize for the missing charts, but we do have those charts on the PSUs that stand out in this roundup.

Cooler Master Real Power Pro 360W & 400W

Cooler Master sent us their new Real Power Pro units with very low wattages of 360W and 400W. There is an additional 500W unit in the series for those that want a bit more oomph. The housing comes in plain black with a very nice looking green sticker on the side. A 120mm fan cools these units. The backside is totally perforated, even around the main switch and AC jack.

Before opening the unit you can already tell who the ODM is, which is why we wanted to have these two new power supplies in our roundup. We have seen many power supplies made by Enhance before, but they are always in the 750W+ market. Cooler Master's Silent Pro series was one of the first to use a newer design from Enhance, and now brings they are the first to use this lower wattage design. Of course, we shouldn't expect too much from such a low-end unit, but Enhance builds nice power supplies. We see a well-equipped power supply with the typical large coils. Teapo makes the capacitors, which we often see on the secondary sides of power supplies. This unit has Teapo on the primary side, which is certainly more for pricing considerations rather than quality.

All but the main ATX cable harness come without sleeving. We have four SATA connectors and five Molex connectors, which is enough for these wattages, and the single 6-pin PEG connector will power your graphics cards if needed. Most companies think if you have a small wattage power supply you will also have a small case; while that is certainly true for many users, we don't understand why many of these power supplies come with harness lengths of around 35cm (14"). The extra 15cm would certainly be beneficial for larger cases, and it wouldn't present a problem for smaller cases either. Cooler Master at least makes the 4-pin 12V connector 50cm long, which is good for people with the jack in unreachable corners of the motherboard. A good motherboard layout will avoid such a problem, but we still see such layout snafus on some of the budget motherboards.

Cooler Master Real Power Pro 360W & 400W - Performance

Cooler Master eXtreme Power Plus 390W

Cooler Master would've never thought about sending us a unit like the eXtreme Power Plus 390W, which is why we got this sample from other sources. It is unfortunately a 230VAC unit only. It comes with passive PFC (no universal AC input), a decent looking grey exterior, and an 80mm fan. We thought it might be a good idea to include it as well since we have several other similar products lined up today. The casing is very simple and the fan grille is cut directly into the metal.

When a power supply has passive PFC, there is always one problem for the designer: where to put the huge passive PFC coil. In this unit they put it on the side, which was possible because the unit slides open to the back. However, it isn't the best location since now most connecting cables need to go through half of the inside above the heatsinks for example. Teapo makes the caps, which is maybe a good choice for this kind of power supply. The eXtreme Power Plus is the only power supply in this roundup that didn't survive the testing since it gave up at 80% load. Good that out Chroma has safety functions that are preventing damages to the equipment but a PC system would have probably not survived at this point.

Buyers of this power supply can expect a short main ATX cable harness and a 55cm long 4-pin 12V harness. That's almost the same as what we saw with both Real Power Pro units. The eXtreme Power Plus comes with two SATA connectors and five Molex connectors, and the cables aren't sleeved. Obviously, this is not a high-end power supply, so the lack of a PEG connector is not surprising.

Cooler Master eXtreme Power Plus 390W - Performance

Corsair CX400W

Corsair's latest product is the CX400W. There is also a new HX450W but we weren't able to get that one in time for our roundup unfortunately. The CX400 is the lowest-end unit from Corsair, which still has enough quality to satisfy even enthusiasts. It comes in black and has a large Corsair logo imprinted in the side panels of the housing. A 120mm Adda fan cools these units. The back is perforated with hexagonal-shaped openings.

The inside reveals a typical Seasonic design with three heatsinks, two for the primary side and the third for the secondary side. Half of the filtering stage is attached to the little sister PCB connected to the other side of the AC jack and then leading onto the main PCB. The primary cap is made by Chemi-Con and the secondary comes from Ostor, a slightly lower end vendor Seasonic uses for these units.

The Corsair CX400W seems to be well equipped with long cable harnesses and plenty of connectors. It is also the only power supply until now with a 4/8-pin 12V connector. It also comes with a 6-pin PEG connector with a length of 60cm (24"). There are six SATA and six Molex connectors as well, which will be good for people with a low-end CPU and GPU but a vast amount of hard drives. The cables are sleeved in black like all Corsair power supplies.

Corsair CX400W - Performance

Corsair VX450W

The VX540W power supply is black as well. It has the same housing as the CX400W, one small difference being the missing small sticker on the front below the AC jack and main switch. It also doesn't have an imprinted logo but a generic sticker as the other older units. It, too, is cooled by a 120mm Adda fan.

Opening this unit reveals the same design as we saw in the CX400W -- the same design but with few changes of components. Instead of Chemi-Con it uses a Hitachi cap, which is not bad since both caps are renowned for their quality.

The VX450 is as well equipped as the CX400W; granted it comes rated at 50W more and plays therefore in somewhat a higher product class, but otherwise the two are very similar. It comes with the same number of connectors, only it has separate 8-pin and 4-pin 12V connectors. All cables are nicely sleeved in black as we are used to from Corsair.

Corsair VX450W - Performance

Enermax Liberty Eco 400W

Enermax has refurbished its older but very successful Liberty series and is now calling it the Liberty Eco. There has also been a bit of cost cutting on the components, but according to Enermax the performance is still the same. We had the Liberty in our labs already a little while back and it performed well. The appearance is still the same as Enermax tries to keep the gunmetal finish (the Liberty Eco is rather black) together with the golden fan grille as their corporate identity. The power supply comes with cable management, though note that the pictures are taken from the 500W version.

The inside doesn't really show anything new since it's a typical Enermax layout. The input filtering stage is as in most cases on a small sister PCB located at the AC jack. The primary side carries a Hitachi cap with 330µF and 400V. The heatsinks are rather small but still big enough to handle the heat for such a lower wattage unit.

Enermax brings the only power supply in this roundup with two 6/8-pin PEG connectors, which is great news for low and medium SLI/CrossFire setups. There are five SATA and five Molex connectors on three cable harnesses. Enermax likes to mix the connectors on each harness so that some people need only one harness to power up hard drives and optical drives. The 12V connector comes with 8-pins but splits in half if you only need four of them.

Enermax Liberty Eco 400W - Performance

Enermax Pro82+ 385W

When we tested the Modu82+ and Pro82+ in the middle of this year, we were very satisfied with the performance both series delivered and awarded both our Gold Editors' Choice Award. We included the Pro82+ 385W version in this roundup to see how it matches up to other models in this category. The power supply comes in a gunmetal finish with a golden fan grille as expected.

The inside is similar to the Liberty series. It also comes with similar components, which might have been the reason why Enermax upgraded the Liberty in the first place, putting the new good ideas from the Pro82+ series into the old Liberty line. Another difference are the Chemi-Con capacitors in the secondary part, which the Liberty Eco doesn't have.

The Pro82+ comes with only one 6-pin PEG connector, since Enermax didn't see the need for more in a 385W power supply even though the 400W Liberty comes with two. We have again three cable harnesses but this time strictly separated into Molex or SATA like the competition. There are four SATA connectors on one cable harness and two cable harnesses with three Molex connectors each.

Enermax Pro82+ 385W - Performance

FSP OEM 300W

Companies such as FSP do not sell these so-called OEM versions directly in the market. Instead, they find their way through various distributors and e-tailers to end-users. They come without any packaging or warranty because the companies want to keep this service strictly to their retail version of the product.

Opening this unit reveals an older topology with passive PFC. There are two main capacitors in the primary with lots of glue around them. The secondary uses Ostor and Teapo capacitors and again lots of glue, which seems to be everywhere in this unit. OEM units don't need to look cool or shiny as we can see with this product here. The heatsinks are small and just might manage to dissipate the heat a 300W PSU can generate. Somewhat funny is the use of a Yate Loon Electronics fan, even though some people see this manufacturer as a high-end option. Obviously, they also offer more economical fan options.

FSP didn't include very many cables and connectors since it is only 300W and an OEM version. Normally companies order power supplies like these to mount them in systems. The manufacturer can vary the length of the harnesses and the number of connectors as the system design requires. The ATX-300PNF comes with a 30cm main ATX harness and the extra 12V connector and the rest of the connectors have a similar short length.

FSP OEM 300W - Performance

FSP Blue Storm II 400W

FSP power supplies sold under their own brand always come in the typical FSP blue paired with a golden fan grille. The Blue Storm II is also one of the older power supplies we are testing today, but it still tries to carry the standard for FSP. We have seen new topologies from FSP that look very interesting and hope they bring out new versions rated at less than 1000W. The Blue Storm II uses a very successful design that FSP has sold to many companies during the past several years. This particular unit might be one of the last survivors of that topology.

This design became famous since it was one of the first ones with heatsinks based on just a piece of aluminum without any fins. The lack of fins should make it difficult for the heatsink to dissipate heat into the air effectively, but somehow it works okay so we don't want to bash too much on this issue. The main capacitor is made by Ostor, which is often used by FSP and Seasonic. The secondary caps are made by CapXon, which we also see often in FSP power supplies. The marking on the PCB shows that this same design is used from 250W up to 500W. It's too bad that we haven't seen a 250W unit with this design in the market; we know many people that would be very happy with such a unit.

As the Blue Storm II is one of FSP's retail products, they equipped it a little bit better than the OEM models. It comes with six Molex and three SATA connectors of decent length. The 24-pin, 4-pin, and 6-pin PEG connectors have a length of 40cm, which is still not very long but better than cables as short as the OEM version. In standard FSP fashion, the cables are sleeved in blue and the PCI-E cable harness is in red.

FSP Blue Storm II 400W - Performance

HEC HEC-350TE-2WX 350W

HEC (or COMPUCASE) has been making power supplies and other products for quite a while now. We have to admit that we never liked anything from the company to date because we have seen mostly passive PFC topologies when active PFC was being utilized by the competition for some time. You can say HEC is conservative with everything they do, as the designs and limited number of retail products suggests. In fact, we always wanted to get retail models from HEC and we were promised them in the past, but they never arrived in our labs. This is why we also acquired this unit from friends rather than HEC itself. It comes in grey and sports two 12V rails with 14A each and a combined power of 276W. It is cooled by a 120mm fan.

Looking inside of this unit shows a similar heatsink design to what we saw in the FSP units. This time they look somewhat massive and at least have the slightest touch of fins. The lack of a large coil suggests active PFC, which makes this unit the first one we have seen from HEC without passive PFC. All the capacitors are made by Teapo and the fan comes from Young Lin Tech.

With HEC we have the same problem as we have seen with the OEM model of FSP. The cables are so short that we can't actually see them being usable in anything other than small Micro ATX chassis. The length of the 24-pin and 4-pin connectors of just 30cm is too short for anything else.

HEC HEC-350TE-2WX 350W - Performance

OCZ ModXStream Pro 400W

The latest addition to OCZ's power supply lineup is the ModXStream Pro series. The 400W version we are testing today is made by CWT while the other power supplies in this series are made by Sirtec. The ModXStream comes with cable management as the name suggests. The housing and the fan grille are black and the back is well ventilated to exhaust air. There are two 12V rails, one with 17A and the second with 14A.

It's a somewhat odd decision by OCZ to let different manufacturers produce their different power supply lines, and now we even have different manufacturers producing models within the same series. Maybe Corsair started this trend by changing to CWT for their higher wattages options (instead of Seasonic), but what OCZ has done here is barely understandable. OCC is currently utilizing FSP, CWT, Seasonic, Sirtec, and Impervio. However, even if the decision is odd it's not a serious concern, since most of these vendors produce high quality products. The inside looks similar to the HEC-350TE-2WX with minor changes to the housing and components. All of the capacitors are made by SamXon and the fan is made by Yate Loon.

The OCZ ModXStream Pro comes with two cable harnesses each with three Molex connectors, and another harness with four SATA connectors. The 24-pin, 4-pin and 6/8-pin PEG connector are 50cm away from the power supply. All cables are of course sleeved.

OCZ ModXStream Pro 400W - Performance

PC Power & Cooling Silencer 370W & 420W

The Silencer series is well known in the enthusiast community, but you rarely see reviews of the smaller 370W and 420W models. These two smaller versions look similar to the bigger brothers with a single 80mm fan at the back of the power supply. They also only come in matte black, while the 750 QUAD is offered in black, red, and blue. The front (i.e. inside the PC chassis) is perforated with long openings to maximize the airflow. The Silencer power supplies use a single strong 12V rail instead of separate 12V rails like all the other units in this roundup.

It's no secret anymore that the Silencer series is made by Seasonic, which includes the 370W and 420W versions as well. Seasonic loves to install cheap heatsinks that consist of an aluminum plate with the fins stamped into shape. It is an effective way to make heatsinks and Seasonic has done well so far, but the problem is that these heatsinks are not really designed for a pull-through cooling system like we see with the Silencer series. It doesn't mean it doesn't work, but with different heatsinks the effect would be better. Maybe this is one area where we should cut them some slack for the sake of cheaper production. The primary capacitor is made by Chemi-Con and the secondary caps are made by Ostor.

Both of the Silencers have the same cable length and number of connectors. The 24-pin, 4-pin, and 6-pin PEG connectors are on 40cm cable harnesses. There are another two cable harnesses with three Molex connectors each, and a final harness with three SATA connectors. The maximum length of 75cm is sufficient for most medium sized chassis.

PC Power & Cooling Silencer 370W & 420W - Performance

Silverpower Gorilla 400W

Maxpoint is responsible for brands like Tagan that have sold well in Europe during the last years. Maxpoint then opened an office in the U.S., which is why Tagan is also available here as well. Silverpower is a newer venture from Maxpoint to cover the lower end market. Maxpoint has the exclusive rights for Seasonic in Europe, which is why the idea came up to ODM from them. The name for this unit is actually not clear since Maxpoint told us Gorilla, or King Kong, or Kong on different occasions. This unit will probably never see the U.S. market but we thought it might be a good addition even if it's only for our readers in Europe.

The Silverpower 400W is based on Seasonic's S12 design. Since we have a 120mm fan in this power supply, the fins needed to be opened and not like the PCP&C Silencer series. In fact, this power supplies is almost the same as the Silencer since they share the same basic topology. Instead of Nippon Chemi-Con, the Silverpower sports a main cap made by Hitachi and the secondary caps are from Ostor.

Maxpoint really equipped the Silverpower Gorilla well, with more cable harnesses and connectors than most of the competition. The main ATX connectors are at the 50cm mark and both (yup - two of them) PEG connectors are at 55cm. The other connectors are spread on two cable harnesses at various distances.

Silverpower Gorilla 400W - Performance

Seasonic S12II 330W

We tested the Seasonic S12II a while back and we liked it so much that we awarded it our Gold Editors' Choice Award. It seems that this series is not doing as well in the market now, since we have heard more negative feedback lately. Now that Seasonic announced an 80 PLUS Gold power supply series for early next year we want to have a last look of this fading series to get a better comparison to other units in this field. It comes in the typical black and with a ventilated back.

Both previously shown units from PC Power & Cooling and Silverpower are made by Seasonic and now we have the retail version from this manufacturer. The design is the same as we saw earlier, but this time we see better components and other small changes. It's clear that an ODM manufacturer also selling its own products wants to have the best components and technology for their retail power supplies. The main cap is made by Hitachi and the secondary caps also come from Japan and are made by Chemi-Con. Seasonic also includes all solid capacitors for the 12V rails. The fan is made by Adda, who supplies most of Seasonic's fans.

The Seasonic S12II 330W comes with the typical six Molex connectors and four SATA connectors. The 6-pin PEG connector is 60cm long, which is good if you want to guide the cable harness nicely through your chassis while trying to optimize airflow. The 24-pin connector is at 55cm, which is good for larger cases.

Seasonic S12II 330W - Performance

Seasonic SS-400ET 400W

We also brought in an OEM version of Seasonic's line up. It comes with the same housing as the S12II but in normal grey. In fact, this unit is almost the same as Seasonic's retail versions, just without a fancy package, painting, cable sleeving, and shorter cables. Unfortunately, these units are not much cheaper which means you can save a few bucks but you won't get the nicer appearance or warranties.

We apologize for the vast amounts of dust you can see on the pictures but this power supply ran quite some time in the office PC of our lab before we decided to include it in this roundup. We see again the same design as the Seasonic S12II, PC Power & Cooling Silencer, and Silverpower units. Surprisingly we found a Chemi-Con capacitor in the primary and Ostor caps in the secondary. The fan is again made by Adda.

The OEM Seasonic 400W is surprisingly well equipped with a 4-pin and 8-pin connector and a 6-pin PEG connector at decent lengths. However, all of the peripheral connectors are short, which means you had better have a chassis where the PSU is mounted in the top and not the bottom. It will be easier (possible) to reach the components this way.

Seasonic SS-400ET 400W - Performance

Silverstone Element ST40EF 400W

The Silverstone Element has been on the market for several years already, and apparently it has been upgraded a few times as the good performance will show on the next page. The package Silverstone put together with the Element is very nice for people who just want the best without compromises. This kind of power supply can only be offered for a certain price, which is the other side of the coin. The Element comes in black like all actively cooled Silverstone power supplies. The rear is nicely perforated for maximum airflow. The front shows several additional longer holes that trapped air exhausts through; that means this warm air will flow back into the chassis but fortunately the exhausted air wasn't very hot while testing.

The Silverstone Element is packed, which we see after opening the housing. There are lots of components and three large heatsinks with fins reaching far over the given space. This power supply is actually heavier than the others, which is due to extra components and larger heatsink volume. We like what Enhance does in its primary sides with the large coil and the little extra care for the rectifier bridge, which usually gets its own heatsink. Teapo makes the primary cap -- an okay choice but there are better options. Teapo also makes the caps in the secondary side and Adda makes the fan.

Silverstone delivers the most extreme cable harnesses with a maximum length of up to 100cm (40"). There are two cable harnesses with a total of six Molex and six SATA connectors. The ATX and PEG connectors have a decent length of 50cm and 55cm.

Silverstone Element ST40EF 400W - Performance

Tagan SuperRock 400W

Tagan sent us their new series, the SuperRock. Whatever the name, this Enhance unit caught our attention. The housing looks similar to Silverstone's Element series and comes in black as usual. The SuperRock has the same perforated front and back which suggests a similar cooling system. The specification shows 24A on the 3.3V rail and 20A on the 5V rail with a combined power of up to 120W. There are two 12V rails with 18A each as well with a combined power of up to 300W.

Tagan delivers the third power supply made by Enhance, but it is a different design. The heatsinks are also much smaller and have less volume. The input filtering stage is packed with components and we have a Chemi-Con cap in the primary side. The fan again comes from Adda.

Tagan provides a very common setup of cable harnesses with two Molex harnesses with three connectors and another single SATA harness with four connectors. This power supply comes with two 6-pin PEG connectors, the first of which is a 6/8-pin PEG connector. All of the harnesses are of decent length.

Tagan SuperRock 400W - Performance

Thermaltake TR2 QFan 400W

Today we will again show the Thermaltake TR2 QFan series since Thermaltake is one of the first manufacturers to show it will listen to end-users. Unfortunately, this series is still not available on the market and various statements from Thermaltake have ranged from "it's already available" to no comment at all. We don't have any clear idea what's going on with this series, but we will be sure to have a chat with the representatives at CES 2009. The first time we saw this series was at CeBIT in Germany this year, but since it's nothing new to find a manufacturer needs a little extra time for a product to hit the market we still aren't worried. The series comes a grayish brown color that looks quite cool. Thermaltake installed their QFan inside for a little extra airflow. We know that this fan can be noisy, even though Thermaltake praises it for very quiet operation.

We have seen quite a lot CWT build power supplies -- the company must have had a hell of year in sales. As far as the QFan, we see minimal components on the input filtering stage and the internals are very sparse in comparison to higher-end PSUs. Of course, if you only need to output 300W to 450W, you don't need a lot of extra components. We find a standard CWT design with three heatsinks, two for the primary side. Thermaltake uses Hitachi capacitors for the primary and SamXon caps on the secondary side. We don't have any complaints about the Hitachi caps, and even though SamXon is a cheaper offering, we haven't encountered any problems with their capacitors in previously tested PSUs.

Cable sleeving begins just beyond where the cable harnesses leave the front of the power supply. We tend to think it looks nicer if the sleeving begins inside the power supply casing, but it's not a huge issue and personal opinion plays a role. Also somewhat odd is that Thermaltake provides the same number of cables and connectors, with identical cable lengths on all of the TR2 power supplies. That means users get plenty of connectors on the 300W model, but the 450W trimmings seem a bit spartan in comparison. We would have liked to see an 8-pin EPS 12V connector or an additional 6-pin PEG connector. Still, there are sufficient Molex and SATA connectors for all kinds of users.

Thermaltake TR2 QFan 400W - Performance

Acoustic Noise Comparison

Our acoustic chart shows four different levels; the first one represents 10% load, the second 20% load, the third 50% load, and the fourth 100% load. We know most of our readers like to see more information in the first half of loading, which is why we chose to show these three levels of loading. Unfortunately, we cannot provide comparisons at specific loads each (i.e. 100W) because in a chart like this with 20 power supplies it becomes confusing and senseless. The color differences indicate relative noise levels: light green means barely audible, darker green will not be audible once the power supply is inside of a chassis along with normal graphics card and CPU coolers, and red means the noise is clearly audible -- in our chart this is from 25dB(A) onwards. The more green a power supply has, the less audible. We use percentages to compare the power supplies which is necessary since most units have a different power output. Loading charts like we use to include in separated reviews makes it impossible to compare many units in one graphic.

Of course, we need to mention at this point again that a quiet power supply will not cool well with higher loadings and ambient temperatures. Noisier power supplies typically mean better cooling for the components. You need to decide for yourself what the most important factor is, but since most people choose PSUs that are far larger than necessary they will not reach anything near the full load results.

Quiet units are quickly visible. First we have the brand new Cooler Master power supplies, then the Corsair VX450W, HEC, the Silencers, Seasonic's S12II, the Silverstone Element, and Tagan's SuperRock. From these very quiet units, both Enhance built power supplies (Silverstone Element and Tagan SuperRock) stick out from the masses. Both are less than 20dB(A) acoustic noise at all times and are therefore "silent" -- or at least close enough that it shouldn't matter.

Efficiency Comparison

The problem most users do not realize today is that if you have lower wattage units you cannot really have the latest technologies inside since it just doesn't make sense. Fancy components and features costs money -- it doesn't matter if they are in an 800W or 300W unit. If you make a small power supply with very high quality features, the user will need to pay for it. The unfortunate truth is that there would be nobody out there willing to pay $150 for a 300W power supply because there are tons of options with prices starting as low as $20. The important thing is to know why you want to have a better quality product, which for most people today is the higher efficiency these units can deliver. If you have a price difference of $50 from your product of choice to a higher efficiency power supply with similar specs, then it will most probably not make any sense since you will need to run the power supply for several years 24/7 to overcome the initial investment.

We discussed this in our article about power consumption and why it is so important to know more about your PC and its components. With today's products we see 82% as a mark every high-end product should be able to reach, which is why we start from 82% with a green graph. Everything below will be red just to show you the efficiency wasn't that good. Don't be worried about the first graph of each power supply since that represents 10% load and no power supply that went through our hands was ever able to come even close to 80% with such a low load. This is why 80 Plus certification for example starts at 20% load. The second graph represents 20% load, the third 50% and the last represents full load. Here again, the more green bars a power supply has the more efficient it is. All of the efficiency results shown are with 230VAC for ease of comparison; efficiency will be slightly lower on 120VAC.

Since the manufacturers are primarily focusing on higher wattage power supplies with new technologies that bring better efficiency, we didn't expect any miracles today. However, some units again stand out from the crowd. Many of the power supplies reach 85% efficiency, which is a very good development. Power supplies from Enermax, OCZ, PC Power & Cooling, Silverstone, and Thermaltake show very good results. The Silverstone Element tops out at incredible 89% efficiency, which puts it at the top of the group a second time.

The following graphic shows the efficiencies below 80% which wasn't possible to include before. Please note the efficiency at 10% load of the FSP OEM unit is with only 61% not visible.

Cable Length - ATX Connectors

The ideal length for power supply harnesses of course depends on the intended use. Someone using a full-size tower will have very different requirements than a user with a micro ATX chassis. As such, we won't provide any commentary on whether the cable lengths are "good" or "bad" in the next four pages. Just try to select a power supply that has cable lengths that are appropriate for your case.

Cable Length - PCI-E Connectors

Cable Length - SATA Connectors

Cable Length - Molex Connectors

Price Comparison

Unfortunately we couldn't find all of our tested units online; those which aren't available right now have their MSRP in dark red. For those units without prices at all we hope we can soon update them after the respective representatives contact us. The first line in each graph shows the price in U.S. Dollars and the second line in lighter red shows the price in Euros.

Units that have been around longer have seen bigger price cuts, so they are often less expensive. The Enermax Liberty Eco MSRP for Europe will be 84.95€ which is very high compared to other similar units. The difference between the Europe and U.S. MSRPs for the Real Power Pro units from Cooler Master is large, but again these are MSRPs and they are likely to drop immediately once they are actually available. Most other units are actually available and are within a $20 radius that pretty much covers all interesting units.

Conclusions

We compared 20 power supplies in the 300W to 450W region today. The decision to write such a large roundup was made based on reader input, since that's what most users actually need for a modern PC. We hope that by including older models as well we have shown a good overview of the market. When people ask us what power supply they should buy in this low wattage segment, we were never really sure ourselves because there are so many different models and unfortunately most of them are complete crap. Users should realize when buying a 500W+ power supply that it simply cannot costs just $30 and still deliver decent quality.

Today, we saw some good models with excellent performance that only cost a few dollars more, and these are the ones worth purchasing. In the following paragraphs, our readers can choose the most important feature(s) and make their decision based on those aspects. In each paragraph, we will select the best option from the 20 power supplies we have tested today. Somewhat interesting to note is that there was only one fatality during testing: the Cooler Master eXtreme Power Plus didn't make it to 100% load and left this world with a loud bang.

Cable Length and Connectors

For some people cables and connectors are the most important factor in choosing a power supply. Let's start with the ATX connectors that include the 24-pin, 8-pin, and 4-pin connectors for the CPU. Most units today only provide the 24-pin and 4-pin connectors. Only two models come with an additional 8-pin connector -- or at least a second 4-pin connector that can combine to form an 8-pin connector. Corsair's VX450W has an additional 8-pin connector and so does the Seasonic OEM 400ET. Some of the units like the HEC model and the OEM unit from FSP have very short 30cm cables, which will be fine for a system builder or perhaps uATX cases but definitely creates issues in larger cases. HTPCs will be another region in which these power supplies would make sense. Cooler Master has mostly 35cm cables, which is also not very good but is still acceptable since the 4-pin connector is 50cm. The longest harnesses are the Corsair VX450W with up to 60cm. Most other units have an average length of 40cm to 50cm.

Anyone that wants to run a modern graphics card with these power supplies needs to check PEG availability first. Most units come with at least one 6-pin PEG connector, which will be sufficient for most midrange systems. The Enermax Liberty Eco, Silverpower, and Tagan SuperRock calm with two connectors each and are capable of running an SLI or CrossFire setup (or a single high-end card with two connectors). The length of these harnesses varies from 40cm to 60cm, which is fine for most systems where the power supply mounts at the top of the chassis.

When it comes down to peripherals, we always hear different opinions. Some users never use more than two connectors, one for the SATA hard drive and the other one for the optical drive. Some might even run a Raid setup and would need three connectors. Who actually needs all the connectors found on most power supplies? If there aren't at least four to six Molex and SATA connectors today, some immediately downgrade the unit, but does everyone need that many connectors? Well, if you run small home-servers or storage arrays for your complete movie or music collection it would makes sense, yes. Our units today come with similar numbers of connectors. Each one has around four to six SATA and Molex connectors, plus one or two Floppy connectors. The length differs tremendously since some units offer only up to 40cm length and Silverstone for example offers up to 90cm, which is excellent for larger cases. If you need a power supply with long cables and plenty of connection options, you should have a closer look at the Silverstone Element; it has the longest cable harnesses in our comparison.

DC Voltage Regulation and Quality

We all know voltage regulation is a vital factor for power supplies and the output quality is something not many companies can handle well. Today power supplies have it easier since motherboards provide their own voltage regulation onboard -- the small black-grayish boxes on the motherboard are the VRMs. With these VRMs, the motherboard controls all of the voltage going to the memory, chipset, and CPU socket. This development raises the question of why we don't have only a single output on power supplies. If you have a laptop then you will recognize that there is a simple power supply typically only provides one voltage, which is around 19V. There are other voltages needed by the system and that is done through these VRMs. We will have to wait and see if a single output specification will hit the industry; until then we are stuck with Intel's ATX standard and multi-output power supplies.

If you focus on stable DC voltages for your system we can recommend several power supplies. Voltage regulation is not a problem today since all the manufacturers from our roundup stayed well within specifications. The best regulation with only around 2-3% comes from Seasonic, and most companies buy from them. In this list, we have first the Seasonic S12II and the Corsair CX400W that do well with lower voltages. The Silverstone Element again comes up with very stable rails, and Cooler Master with the Real Power Pro looks impressive starting strangely with lower voltages and building slowly up to a higher level. PC Power & Cooling and Seasonic both have very stable 12V rails, which is even more important than the 3.3V and 5V rails.

The output quality is another important factor and here we see larger differences because high ripple is something every company needs to address. For example, the Cooler Master eXtreme Power Plus goes way out of spec with the 3.3V and 5V rail. The OCZ ModXStream Pro is also quite above spec with its lower voltage rails and the Seasonic OEM unit could not run within specs. On the 12V rails, the headroom is a little higher and all companies stay below 100mV where 120mV is allowed.

Efficiency

Today everyone is talking about being green and saving the planet with energy-efficient products. The efficiency is very important for most people since it not only shows that power supplies don't waste too much energy but also is a good indication of quality. To reach higher efficiencies the manufacturer needs to have a well designed PCB with good components. Higher efficiency is impossible to reach for example with an older design with passive PFC. We have seen lately very nice power supplies with up to 90% efficiency, and soon Seasonic will even have the first power supplies with 80 Plus Gold certification in the market. We have published several articles that explain about the pros and cons of this efficiency-hype at the moment and when it would be worth it to spend more money on a new higher efficiency power supply and when not.

It is very important that you know what kind of load your PC will work with most of the time when choosing a power supply. Most power supplies are most efficient with around half of their rated output (50% load). Checking our efficiency results we see that both units with passive PFC have very low efficiency, which means they are poor choices. If you need high efficiency, you are best off with the Silverstone Element that achieves up to 89% efficiency. Then the PC Power & Cooling Silencers are also very good with up to 86% efficiency and 85% in the lower regions of 20% load. The Enermax Pro82+ and Liberty Eco also operate efficiently and get our third and last recommendation.

Acoustic Noise

Acoustic noise is another field where we see strong opinions on both sides. Years ago that was not an issue at all because if you built a system yourself you didn't have a choice for silent components -- especially not the choice we have today. Most companies took a brute force approach to cooling, with powerful but noisy fans to counteract high heat levels. Today this situation has fortunately changed. There are numerous passively cooled products out there and companies like AMD and Intel try to develop energy efficient products as well as maximum performance options. The whole market has changed, which is why we have phrases like "silent computing".

Power supplies do get hot when operating at high loads; that is a fact. This heat needs to be exhausted from the housing and that requires a fan. When you have less heat you can lower the airflow inside of the power supply, which is why we have mostly low acoustic noise at lower loads. If you care about finding a quiet power supply, you should first start by choosing the right wattage to make sure it's not fully loaded during normal operation.

Our test results have shown that the Silverstone Element and the Tagan SuperRock are among the quietest power supplies in our roundup today. There are other models with low acoustics as well, for example the Seasonic S12II, the two new Cooler Master Real Power Pros, and the PC Power & Cooling's Silencers. All of these remain generally quiet even with higher loads; there's no aggressively audible noise creating pain for your ears.

Prices

As stated already, we were not able to get price quotes on all of the power supplies today. Some are not yet available, some are only offered in some parts of the world, and for others the representatives weren't able to get us a price in time. We will update prices as soon as they are available. For now we have US and Euro prices and the differences are rather big. The Silverstone Element was not available in the U.S. anymore, unfortunately, but Silverstone is getting together with Newegg to reintroduce the power supply.

Of course some of the units are very cheap, but looking at the performance we don't recommend and will never recommend flawed products. There are power supplies such as the Corsair CX400W that didn't stick out too much during testing but still offer a very attractive price tag. If you do have only around $50 to spend on a power supply we suggest you have a closer look at the Corsair CX400W, or the OCZ ModXStream Pro with 400W if you want cable management. OCZ must have something wrong with the prices right now, since this power supply costs much more in Europe than in the U.S. -- although that cheaper price of $55 might only be for Newegg since other shops show $75 and more.

If you want the best performance and the price is a secondary priority, we definitely recommend the Element series from Silverstone. This power supply managed to top both the noise and efficiency charts, and delivered good results across the board. If you aren't able to buy the 400W version in the country where you live, go for the 500W version instead. However, we do hope that Newegg and other e-tailers will begin selling the 400W model again.