Test Setup

All measurements are performed utilizing ten electronic loads (seven Array 3711A, 300W each, and three Array 3710A, 150W each), which are able to deliver over 2500W of load and are controlled by a custom made software. We also use a Picoscope 3424 oscilloscope, a CHY 502 thermometer, a Fluke 175 multimeter and an Instek GPM-8212 power meter. Furthermore, in our setup we have included a wooden box, which along with a heating element is used as a Hot Box. Finally, we have at our disposal four more oscilloscopes (Rigol 1052E and VS5042, Stingray DS1M12 and a second Picoscope 3424) and a CEM DT-8852 sound level meter. In this article you will find more details about our equipment and the review methodology we follow. Finally, if the manufacturer states that the maximum operating temperature of the test unit is only 40°C then we try to stay near this temperature, otherwise we crank up the heat inside the hotbox up to 45-50°C.

Voltage Regulation Charts

The following charts show the voltage values of the main rails, recorded over a range from 60W to the maximum specified load, and the deviation (in percent) for the same load range.

5VSB Regulation Chart

The following chart shows how the 5VSB rail deals with the load we throw at it.

Efficiency Chart

In this chart you will find the efficiency of ERV850EWT-G at low loads and at loads equal to 20-100% of PSU’s maximum rated load.

Voltage Regulation and Efficiency Measurements

The first set of tests reveals the stability of voltage rails and the efficiency of ERV850EWT-G. The applied load equals to (approximately) 20%, 40%, 50%, 60%, 80% and 100%, of the maximum load that the PSU can handle. In addition, we conduct two more tests. In the first we stress the two minor rails (5V & 3.3V) with a high load, while the load at +12V is only 2A and in the second test we dial the maximum load that +12V can handle while load at minor rails is minimal.


The PSU performed identically to the Enermax Platimax 850W PSU, which we reviewed before. This was expected, since both units use the same platform. So like its Platinum brother this unit registered loose voltage regulation at 3.3V, where it got dangerously close to the 5% limit. The +12V rail managed to stay within 2%, a good result; and 5V was right at 3.51%, not bad but not so good either. As you can see efficiency is pretty high and is in- between Gold and Platinum levels. Also the PSU clearly proved that it can deliver its full power continuously even at ultra-high operating temperatures, effortlessly. Although we stressed the unit really hard, in order to raise the internal temperature of the hotbox, the cooling fan started to make its presence felt only from 80% load and beyond. In normal ambient temperatures inside a PC case this unit's fan will work at low RPMs so most likely it will be the last thing you will be able to hear of the whole system. Unless of course you have superman's hearing!

Efficiency at Low Loads

In the next tests, we measure the efficiency of ERV850EWT-G at loads much lower than 20% of its maximum rated load (the lowest load that the 80 Plus Standard measures). The loads that we dial are 40, 60, 80 and 100W (for PSUs with over 500W capacity). This is important for scenarios in which a typical office PC is in idle with power saving turned on.


Efficiency at loads lower than 20% of max rated capacity is very good and even with 40W load the unit registers a close to 76% reading. From 60W and upwards all efficiency readings exceed 80%, so this PSU will save you some money from electricity bills even at very low loads.

5VSB Efficiency

ATX spec states that the 5VSB standby supply's efficiency should be as high as possible and recommends 50% or higher efficiency with 100mA load, 60% or higher with 250mA load and 70% or higher with 1A or more load.
We will take four measurements, three at 100 / 250 / 1000 mA and one with the full load that 5VSB rail can handle.


In the first three tests the 5VSB registered good efficiency levels while at the last one efficiency dropped a little bit, compared to test#3, but still is above the respective limit. 3A on this rail is close to the limit and most likely 2.5A is the sweet spot for good efficiency and below 4% voltage regulation.

Power Consumption in Idle & Standby

In the table below you will find the power consumption and the voltage values of all rails (except -12V), when the PSU is in idle mode (On but without any load at its rails) and the power consumption when the PSU is in standby (without any load at 5VSB).


This unit's vampire power is much lower than the 1W limit that the ErP Lot 6 2010 directive sets. To be more specific it's about one fifth of the aforementioned limit so Enermax hit the right spot here.