NZXT C Series 850W Power Supply Review

The NZXT C series power supply with 850W capacity has high build quality and performs well in almost all sections.

NZXT C Series 850W
(Image: © Tom's Hardware)

Why you can trust Tom's Hardware Our expert reviewers spend hours testing and comparing products and services so you can choose the best for you. Find out more about how we test.

To learn more about our PSU tests and methodology, please check out How We Test Power Supply Units. 

Primary Rails And 5VSB Load Regulation

The following charts show the main rails' voltage values recorded between a range of 40W up to the PSU's maximum specified load, along with the deviation (in percent). Tight regulation is an important consideration every time we review a power supply because it facilitates constant voltage levels despite varying loads. Tight load regulation also, among other factors, improves the system’s stability, especially under overclocked conditions and, at the same time, it applies less stress to the DC-DC converters that many system components utilize.

Load regulation is tight on all rails. 

Hold-Up Time

Put simply; hold-up time is the amount of time that the system can continue to run without shutting down or rebooting during a power interruption.

With close to 21ms hold-up time, the corresponding ATX requirement is easily met. The power ok signal is accurate, too. 

Inrush Current

Inrush current, or switch-on surge, refers to the maximum, instantaneous input current drawn by an electrical device when it is first turned on. A large enough inrush current can cause circuit breakers and fuses to trip. It can also damage switches, relays, and bridge rectifiers. As a result, the lower the inrush current of a PSU right as it is turned on, the better.

The inrush current is low with 115V and at normal levels with 230V. 

10-110% Load Tests

These tests reveal the C850's load regulation and efficiency levels under high ambient temperatures. They also show how the fan speed profile behaves under increased operating temperatures.

Swipe to scroll horizontally
Test #12V5V3.3V5VSBDC/AC (Watts)EfficiencyFan Speed (RPM)PSU Noise (dB[A])Temps (In/Out)PF/AC Volts
15.263A1.984A1.984A0.984A84.95686.711%0<6.0 45.23°C0.953
12.038V5.042V3.325V5.081V97.976 40.77°C115.19V
211.560A2.977A2.981A1.184A170.02489.821%0<6.0 46.22°C0.973
12.034V5.039V3.324V5.069V189.291 41.04°C115.19V
318.200A3.474A3.475A1.384A255.02890.500%5379.5 41.20°C0.982
12.032V5.038V3.322V5.058V281.800 47.07°C115.18V
424.844A3.971A3.977A1.585A340.03390.610%5439.6 41.56°C0.985
12.028V5.038V3.320V5.047V375.273 48.25°C115.18V
531.139A4.967A4.975A1.787A424.86890.299%5579.9 42.04°C0.987
12.022V5.035V3.318V5.036V470.511 49.09°C115.18V
637.421A5.964A5.972A1.991A509.39089.661%81819.5 42.83°C0.988
12.014V5.032V3.316V5.023V568.132 50.85°C115.17V
743.785A6.960A6.970A2.194A594.69988.841%119731.4 43.27°C0.989
12.004V5.030V3.314V5.012V669.397 51.81°C115.17V
850.161A7.957A7.969A2.399A680.03688.099%166439.4 43.73°C0.990
11.994V5.029V3.312V5.000V771.904 53.27°C115.16V
956.927A8.455A8.456A2.403A764.93387.297%206044.3 44.30°C0.991
11.988V5.027V3.310V4.994V876.238 54.52°C115.16V
1063.437A8.957A8.974A3.016A849.74486.349%208644.6 45.52°C0.992
11.981V5.025V3.309V4.974V984.086 56.57°C115.15V
1170.541A8.963A8.980A3.020A934.49785.244%209644.8 46.84°C0.992
11.976V5.021V3.307V4.966V1096.260 58.77°C115.14V
CL10.100A11.999A11.999A0.000A101.44384.686%563 10.1 42.45°C0.961
12.041V5.034V3.320V5.088V119.787 49.45°C115.19V
CL270.002A0.999A1.001A1.000A851.70486.788%2087 44.6 45.75°C0.991
11.976V5.026V3.311V5.025V981.364 56.69°C115.14V

There is no problem, at all, under high operating temperatures. The fan has to work at high speeds, though, to handle the heat load and this leads to loud operation. 

20-80W Load Tests

In the following tests, we measure the C850's efficiency at loads significantly lower than 10% of its maximum capacity (the lowest load the 80 PLUS standard measures). This is important for representing when a PC is idle with power-saving features turned on.

Swipe to scroll horizontally
Test #12V5V3.3V5VSBDC/AC (Watts)EfficiencyFan Speed (RPM)PSU Noise (dB[A])PF/AC Volts

With the semi-passive operation active, there is no need for the fan to spin under light loads, even at higher than 35 degrees Celsius ambient temperature.

2% or 10W Load Test

Intel plans on raising the ante at efficiency levels under ultra-light loads. So from July 2020, the ATX spec will require 70% and higher efficiency with 115V input. The applied load is only 10W for PSUs with 500W and lower capacities, while for stronger units we dial 2% of their max-rated-capacity.

Swipe to scroll horizontally
Test #12V5V3.3V5VSBDC/AC (Watts)EfficiencyFan Speed (RPM)PSU Noise (dB[A])PF/AC Volts

The C850 achieves high efficiency with 2% load, if its max-rated-capacity, but it cannot reach 70%.


Next, we plotted a chart showing the C850’s efficiency at low loads, and loads from 10 to 110% of its maximum-rated capacity. The higher a PSU’s efficiency, the less energy goes wasted, leading to a reduced carbon footprint and lower electricity bills.

In the 10-100% load tests the overall efficiency doesn't meet the competition, but the overall efficiency score, which takes into account more than 1500 different load scenarios, tells a different story. With light and super-light loads, the C850 scores betters in our charts. 

5VSB Efficiency

Swipe to scroll horizontally
Test #5VSBDC/AC (Watts)EfficiencyPF/AC Volts

The 5VSB rail has satisfactory efficiency, which could be further increased, though. 

Power Consumption In Idle And Standby

Swipe to scroll horizontally
Idle & Standby Power Consumption
Mode12V5V3.3V5VSBWattsPF/AC Volts

The vampire power levels are low in both cases (115V and 230V).

Fan RPM, Delta Temperature, And Output Noise

All results are obtained between an ambient temperature of 37 to 47 degrees Celsius (98.6 to 116.6 degrees Fahrenheit).

(Image credit: Tom's Hardware)

(Image credit: Tom's Hardware)

Under high operating temperatures, the fan profile is definitely aggressive and the semi-passive mode doesn't last long. The PSU's compact dimensions don't help airflow and on top of that don't allow for a larger cooling fan. 

The following results were obtained at 30 to 32 degrees Celsius (86 to 89.6 degrees Fahrenheit) ambient temperature.       

(Image credit: Tom's Hardware)

(Image credit: Tom's Hardware)

At normal ambient temperatures, the semi-passive operation doesn't last for long, as is the case with higher temperatures. The fan has a less aggressive speed profile in these conditions. It takes more than 600W load for the PSU to exceed 30 dBA noise output.

MORE: Best Power Supplies

MORE: How We Test Power Supplies

MORE: All Power Supply Content

Contributing Editor

Aris Mpitziopoulos is a Contributing Editor at Tom's Hardware US, covering PSUs.