1500W Power Supplies: Thermaltake and Xigmatek Solutions Reviewed

Today we will talk about two power supply units of gigantic capacity: Xigmatek "No Rules Power" NRP-HC1501 and Thermaltake Toughpower 1500A W0171.

by Oleg Artamonov
04/02/2009 | 02:07 PM

After reaching the 1500W milestone, PSU developers have taken a break. Whether it is because they cannot put more power into the dimensions of a regular computer power supply or because even their marketing departments have come to realize the uselessness of even higher wattages, but I can see only a few 1500W models and no models with higher wattage selling freely today.


Some time ago I tested Thermaltake’s 1200 and 1500W units (based on the same platform) and was left disappointed. The low stability of their output voltages prevented me from getting the full specified output power from them. However, later on I tried a Corsair HX1000W, which was also based on a similar platform, and had much better results. So, I have a suspicion that these high-wattage PSUs were not quite good in the first batch but improved later.

Today I will be able to check my suspicions by testing two products: Xigmatek “No Rules Power” NRP-HC1501 and Thermaltake Toughpower 1500A-01 W0171. Both have a wattage rating of 1500W.

Testing Methodology

Click the following link for a description of our testing methodology and equipment and a brief explanation of what the specified and tested parameters of power supplies mean: X-bit Labs Presents: Power Supply Units Testing Methodology In-Depth. If you feel overwhelmed with the numbers and terms this review abounds in, check out an appropriate section of the mentioned article for explanation.

You can also go to our Cooling/PSU section to read reviews of other PSU models we have tested in our labs.

Xigmatek “No Rules Power” NRP-HC1501

Although Thermaltake comes earlier in the alphabet than Xigmatek, I will begin with the latter. After all, it is the first time this PSU comes to our labs. Moreover, we don’t often have a chance to test Xigmatek’s products.


The PSU comes in a huge light-silver box with a carry handle. The latter is most appropriate considering the dimensions and weight of the box. The model’s name and features are printed on one of the sides.

The silvery box is just an external wrapper, though. Under it is a black box without any text.

And when you open it up, there is a third box! It is black again but with a company logo. Fortunately, this box is the last one and contains the power supply. This box-in-a-box structure has no practical value, but is surely original.

Besides the PSU, there is a user manual, power cord and fasteners here.

The manufacturer also offers a pouch for storing the detachable cables and a fabric purse for the power supply itself. I can’t imagine someone using the purse, though. Do you know many people who buy 1500W power supplies to put them away?

Exterior Design

Despite the impressive dimensions of the box, the PSU is large but not huge. It is 200 millimeters long, which is 60 millimeters longer than the standard ATX unit but, for example, 20 millimeters shorter than the Chieftec Super Series.

The PSU has a perfectly standard housing except that the On/Off button is larger than usual. It is cooled with a single 140mm fan.

As you can see in the photo, some of the vent holes are blocked with plastic film from the inside of the PSU case. Running a little ahead, I can tell you that this is electric insulation of the standby source. Although this film has a negative effect on cooling, the engineers just had no choice.

Some of the PSU’s cables are detachable. There are nine Molex Mini-Fit Jr. connectors for them: six for graphics card cables and four for peripheral cables. The connectors differ in color as well as in the position of the keys, so you won’t be able to plug an HDD cable into a connector for a graphics card cable by mistake.

The color of the graphics card connectors, red or blue, indicates what +12V line the connector belongs to. Unfortunately, the PSU label does not explain this, and you have to look up in the user manual or on the cables (their connectors differ in color, too).

The PSU has highlighting for the On/Off button and fan.

Circuit Design

The interior design is instantly recognizable. It is the well-known platform developed and manufactured by Channel Well. It is also used in the 1500W unit from Thermaltake (which will be discussed later in this review) as well as in 1000W and higher power supplies selling under several other brands.

The photo shows clearly the symmetric design of the PSU. You can divide it along the middle into two identical halves. These are actually two power supplies, each for 750W, within a common housing.

The sub-PSUs are only connected by the turn-on circuit because they are started up simultaneously. Each sub-PSU has an active PFC device (the PFC chokes can be seen between the heatsinks in the photo), PWM controller, power transformer, and output rectifiers. In other words, if you take the NRP-HC1501 apart and unsolder about half the components, it will work like a regular 750W power supply.

The single important difference between the sub-PSUs is the selection of voltages they provide. One yields +12V and +5V while the other, +12V and +3.3V. The +5V and +3.3V voltages are generated by dedicated switching regulators mounted on small cards (one such card can be seen in the photo above). These are full-featured power sources with a PWM controller, choke, synchronous rectifier and smoothing capacitors. Each source lowers the input +12V voltage to the necessary level. Thus, the NRP-HC1501 implements dedicated voltage regulation.

The controllers of the main regulators of the sub-PSUs are located on small separate cards and based on Champion Micro CM6800G chips.

And there are two more cards (one for each sub-PSU) with a fan controller and overload & overvoltage protection. Since there is only one fan in the PSU, one card only controls the currents and voltages of its sub-PSU.

In fact, there is nothing extraordinary about the design of each of the sub-PSUs. Excepting the step-down regulators for +5V and +3.3V voltages, they are ordinary modern power supplies with active PFC. And the regulators are used to save space in the first place. The component density is high, and the more widespread design for providing +5V and +3.3V in mainstream and top-end power supplies – by means of saturated-core chokes – just would not fit into the housing. The regulators employed here are more complex and expensive but are implemented as a narrow card that can be easily installed at the side panel of the case.

So, it is the joining of two virtually independent power supplies within one housing that is the unique idea here. But I doubt it will ever be really popular among the manufacturers. This design is complex and expensive and the load must be distributed symmetrically between the sub-PSUs’ outputs in order to get the full output power from the PSU. Moreover, such a high wattage is not actually needed by modern computers.

There is one more card near the external vent grid. It carries the standby source which is shared by both sub-PSUs.

KY series capacitors from United Chemi-Con are installed at the PSU’s output. This company’s products enjoy good reputation, but the KY series has the highest ESR rating among all the series intended for switching power supplies. PSU makers usually prefer the KZE series which has lower ESR.

Cables and Connectors

The PSU offers the following cables and connectors:

The cables are sleeved. The wires of different cables only tangle near the PSU case.

Included with the PSU are:

Although the graphics card cables have 6-pin or 8-pin connectors on both ends, you must plug them in a specific way. There is a paper sticker near each connector indicating whether it goes into the graphics card or power supply. I don’t quite grasp the purpose of this solution. It would be simpler to put identical connectors on both ends of the cable.

The manufacturer might have also included one more cable with SATA power plugs into the box. The PATA interface has already become obsolete together with its 4-pin power connector, and it would be better for a new PSU to offer more SATA plugs. Two cables with four connectors on each may be not enough if you are going to install the NRP-HC1501 into a system case with a couple of optical drives and a serious disk array with five or six HDDs.

It is all right with the graphics card cables: the eight available connectors can be used to power four top-end cards simultaneously. Four connectors are of the 6-pin variety, and the other four are 6+2-pin ones.


The PSU offers a peak continuous output power of 1500 watts, but you can only achieve this load on a testbed. Not only because modern computers consume much less, but also because these 1500 watts must be equally distributed between the two sub-PSUs described above – 750 watts for each.

The PSU has two truly independent +12V power rails each of which is additionally divided into two “virtual” lines. The different lines have different peak currents. The 12V3 and 12V4 lines offer the most amperes and it is to them that the detachable graphics card cables are connected (up to six cables).

The allowable distribution of load among the different power rails matches the overall output power of the PSU.

UPS Compatibility

Together with an APC SmartUPS SC 620 this power supply worked at loads up to 385W when powered by the mains. The pair switched to the batteries normally but was not stable then. It is only at a load of 300W that the UPS could work for more than a minute.

Thus, the power supply is compatible with UPSes but the UPS must have a reserve of wattage in order to ensure stability.

Voltage Stability

Although the PSU offers two independent +12V power rails, the latter are designed in the same way and have similar parameters. Therefore I will only show you the test result for the 12V1+12V4 rail below. The voltage on the 12V2+12V3 rail differs by only a tenth of a volt under the same load.

Our testbed can ensure loads up to 1300W, with up to 1100W on the +12V rail. That’s why I did not test the PSU at its maximum load, limiting myself to the capabilities of the testbed.

The PSU was connected to the testbed with a mainboard connector, one SATA power plug (the ground and +3.3V pins only), two PATA connectors, three 6-pin graphics card connectors and an 8-pin CPU connector. All the pins in every connector were used, save for the SATA plug.

Thermaltake’s power supplies that used the same dual design from CWT had very poor results in my earlier tests. Their voltages sagged quickly under load, making it hard to get even 1000 watts from the PSU. And it did not seem to be a defect of the particular sample because both products I tested then had identical results.

Channel Well’s engineers seem to have introduced some innovations since then. At least, the Xigmatek NRP-HC1501 has very stable voltages. The +12V rail boasts excellent stability, staying within a 1% deflection through the biggest part of the diagram. The +5V voltage fits within a 3% deflection, and the +3.3V voltage is the only one to violate the permissible 5% deflection – but only at near-1300W loads. The latter thing may be partially our testbed’s fault, though. I guess such a high-wattage power supply should be connected to the testbed with even more connectors in order to reduce the voltage drop on the “ground” wires.

Summing it up, the Xigmatek NRP-HC1501 has no problems with delivering stable voltages.

Output Voltage Ripple

The high-frequency pulsation on the +12V rail is within the norm. On the +5V rail the ripple is occasionally as high as the permissible maximum of 50 millivolts. There are periodic spikes above the 50-millivolt limit on the +3.3V rail but they are not as high as to cause any problems.

Fan Speed Management

The PSU is equipped with a 140x140x25mm Yate Loon D14BH-12 fan. Notwithstanding the huge wattage of the NRP-HC1501, it does not have auxiliary fans.

This is an ordinary 7-blade fan with ball bearings. According to Yate Loon, its rated speed is 2800rpm.

The fan speed is constant at 1000rpm until a load of 600W. The PSU is not quiet then, but will satisfy most users. Fans of many other power supplies, starting from 400W models, work at the same or even higher speed under low loads.

When the load grows higher, the fan speed increases linearly, reaching a maximum of 1900rpm. That’s quite a modest top speed for a fan of such a high-wattage PSU. I personally have seen louder PSUs. Of course, the fan is quite noisy at 1400rpm (800W load) and higher speed, but I don’t think it is easy to create such a high load in a real computer while keeping the other components, besides the PSU, quiet.

The temperature difference at the input and output of the PSU is quite normal: less than 14°C at a load of 1300W.

Thus, notwithstanding its huge wattage the Xigmatek NRP-HC1501 is quite a good modern PSU in terms of noisiness. People who love silence should consider specially optimized models instead.

Efficiency and Power Factor

The PSU boasts high efficiency at medium loads – over 85%! The efficiency is lowering towards higher loads, dropping below 80% at 1250W.

+5Vsb Standby Source

Starting from this review I will test the ability of the PSU’s standby source to cope with the specified load. This test is performed when the PSU is turned off, the +5Vsb source being the only working component in it.

The NRP-HC1501 passes this test (the voltage must be within 5% from 5V) but the voltage sags noticeably, to 4.8V almost, under full load. To remind you, the +5Vsb source powers various USB devices when the computer is in sleep mode (for example, to provide the option of turning the system on from the keyboard). It also powers system memory in Suspend-to-RAM mode (S3).


I will not argue here if 1500 watts of power are really necessary for real-life computing because we are going to dedicate a special review to this problem. Let’s assume they are. Will the Xigmatek NRP-HC1501 be able to provide them? According to my tests, yes. Although our testbed could only load it by 1300W due to the testbed’s limitations, there is no reason for me to think that an extra 200W would change anything in the overall picture. The PSU delivers stable voltages with acceptable voltage ripple and does not heat up much. It has large, but not extremely large, dimensions, and is equipped with all the connectors you may want (perhaps one more SATA power cable would be appropriate).

It is also good that, despite its high wattage, the NRP-HC1501 is no noisier than typical modern PSUs. It will satisfy the majority of not-very-demanding users in this respect.

Thermaltake Toughpower 1500A-01 W0171

In an earlier review I was greatly disappointed with Thermaltake’s PSUs that used the same dual design because they delivered very unstable voltages but the Xigmatek NRP-HC1501 is free from such problems. Does it mean that Xigmatek gets somewhat different PSUs than Thermaltake (this is possible) or Channel Well engineers have introduced some changes to get rid of the drawbacks of the early batches of such PSUs?

I will check this out by testing a market opponent to the NRP-HC1501. It is the 1500W Toughpower W0171 model from Thermaltake.


Thermaltake’s packaging is far more picturesque, but trivial in design if you compare it with Xigmatek’s box-in-a-box solution. A carry handle would be appropriate considering the size and weight of the box, but there is none.

When you open the package up, you can see the power supply and its accessories.

Besides screws and a power cord, there is a nice pouch for storing detachable cables and a silicone vibration-absorbing pad you can put on the PSU before installing it into your computer.

Unfortunately, this pad is not compatible with many system cases. If there are any ledges, stiffness ribs or other protrusions on the back panel of the case, the pad will prevent you from installing the PSU. On the other hand, its practical value is not high. The pad does not allow PSU’s vibration to pass to the system case, but such a strong vibration can only be caused by a defective fan. And defective fans are but very rare in Thermaltake’s PSUs as far as I know.

Exterior Design

The PSU looks exactly like the above-discussed Xigmatek except for the stamped word Thermaltake and the special fan grid.

The grid is beautiful but impractical. It has a larger surface than the wire grid of the Xigmatek unit, thus offering higher aerodynamic resistance and worsening the cooling of the PSU. I also think it worsens the level of noise (not more than by 1 or 2 decibels, though). Well, it is not the first time I see an aerodynamically odd solution from Thermaltake.

Besides, Thermaltake’s PSU only has a highlighted On/Off button. The fan has no highlighting.

The PSU has six connectors for graphics card cables and four connectors for peripheral cables. As opposed to the Xigmatek model, it is clear why the graphics card connectors are different colors: they are connected to different +12V lines (12V3 and 12V4) – and the PSU label shows to which exactly line each of the connectors belongs.

Circuit Design

It is not easy to take this PSU part because some of its screws are hidden under the label.

It wouldn’t be much of a problem if the label were not made from an aluminum plate. It is hard to tear it off the PSU and even harder to make the PSU look nice after such disassembly. The typical paper sticker Warranty Void If Removed looks like a child’s toy in comparison.

There is nothing new inside. The PSU only differs from the above-discussed Xigmatek with the color of its heatsinks (and this color has no effect on cooling because the PSU is equipped with a fan). It is the same platform developed and manufactured by Channel Well: two 750W power supplies in a single housing.

There is no point in describing this PSU in detail – you can just refer to the description of the Xigmatek NRP-HC1501 above.

Cables and Connectors

The PSUs differ a little in connectors. The Thermaltake has the following:

Included with the PSU are:

So, the difference is that the Xigmatek offers universal 6+2-pin connectors for graphics cards whereas the Thermaltake offers 8-pin connectors and adapters for 6-pin connectors. Xigmatek’s solution is handier and more reliable.

The cables are designed in the same way in both PSUs, up to the stickers that indicate what end of a power cable goes into the PSU and what +12V line the connector of a particular color belongs to.


The specs are exactly the same as those of Xigmatek’s PSU. The PSU is rated for a total output power of 1500 watts and consists of two sub-PSUs, each with a peak load of 750W. It offers two independent +12V rails, each of which is additionally separated into two “virtual” output lines.

UPS Compatibility

Together with an APC SmartUPS SC620 the power supply worked at loads up to 385W when powered by the mains. They switched to the batteries normally but were not stable – the UPS could work more than 1 minute on the battery only at loads up to 300W. So, there is no difference from the Xigmatek unit in this test.

Voltage Stability

Now we’ve come to the most interesting test. Thermaltake’s power supplies based on this platform demonstrated very poor results before. The Xigmatek has shown good performance in this test – perhaps Thermaltake’s PSUs have improved, too?

They have improved indeed. The +12V voltage has excellent stability throughout the entire load range. The +5.5V voltage is within a 4% deflection (while the industry standard allows a 5% deflection). The +3.3V voltage is the only one to violate the allowable limit, but only under extremely high loads which are impossible in modern computers (a typical combined load on the +5V and +3.3V rails is only 50-60W in a modern PC).

Output Voltage Ripple

The voltage ripple is higher on the +12V rail than with the Xigmatek PSU, but acceptable. The +5V voltage is within the norm, too. There are spikes on the +3.3V rail above the permissible limit, but that shouldn’t be a problem. Thermaltake’s 1500W units I tested before had much stronger pulsations.

Fan Speed Management

The PSU is equipped with a 140x140x25mm Yate Loon D14BH-12 fan. The Yate Loon site says the fan has a rated speed of 2800rpm, but a similar fan works at a lower speed in the above-discussed PSU from Xigmatek.

The Thermaltake is noisier than the Xigmatek unit but the difference in fan speed is small and must be due to the variation in the real parameters of employed components. The Thermaltake also has a pretty-looking but aerodynamically poor grid of the fan. The PSU is not silent but quite comfortable, considering its huge wattage.

Efficiency and Power Factor

The PSU is up to 86% efficient at medium loads and 80% efficient at high loads. It has the same result as the Xigmatek PSU.

+5Vsb Standby Source

The standby source copes with loads up to 3.5A, which is quite normal for today. Its voltage changes greatly depending on load, but does not violate the permissible limits.


I can note two things here. First, the reputation of the Thermaltake Toughpower W0171 power supply is restored. And second, it differs but slightly from the Xigmatek NRP-HC1501 model. If you think your computer needs a power supply of such a high wattage, you can buy a W0171 without any fear: it is a high-quality product with stable operation and comfortable level of noise.


I had had some apprehensions before this test session, but the PSUs both eliminated them completely. The only thing I can point out is that 1500 watts of power is not really needed today. Configurations that might need so much power have no point in terms of performance. As our tests show, triple-GPU subsystems are not faster than dual-GPU ones.

But if you do think you need such a high-wattage PSU, any of the two tested models will make a good buy. They have good electrical parameters, deliver stable voltages with acceptable voltage ripple and are comfortable in terms of noisiness (comparable to modern mainstream 600-700W models). The poor compatibility with UPSes may be a problem but you can solve it by purchasing an UPS with a reserve of wattage.

The two PSUs from Thermaltake and Xigmatek are both based on the same platform developed by Channel Well and are in fact twin brothers in quality and electrical parameters. The Xigmatek is somewhat better in functionality: it has universal graphics card connectors, a highlighted fan, and a slimmer fan grid that creates less noise. The difference between the two models is really negligible, though.