I always like knowing what’s going on with my PC, but I tend to only focus on its cooling capabilities, since that directly affects whether my system sounds like a purring kitten or a jet engine while I’m working (or gaming). However, I’ve always been curious to know how much power my system draws, since I tend to leave it on longer than I probably need to throughout the day.
While it’s easy to measure the power draw of any appliance by picking up a handy reader—the Kill A Watt, for example, or something quick and easy like the Belkin Conserve Insight I use—you might want to consider a more fun and thorough solution if you’re looking to upgrade your desktop system (or build a brand-new one). I’ve been playing around with NZXT’s E850 digital power supply and system-monitoring CAM software, and both have taught me a lot about my system’s power requirements.
Power supplies are sexy
NZXT’s digital power supply works like any other power supply, save for one slight modification. In addition to the normal bevy of modular connections you use to power your various components, the power supply also has a standalone USB-C connection. This plugs directly into one of the free USB headers on your motherboard (assuming you have one), and allows the power supply to output data on what it’s doing to NZXT’s accompanying (free) CAM software.
In general, CAM is similar to tools like Speedfan, CPU-Z, GPU-Z, HWMonitor, or whatever other apps you use to monitor your PC’s components. On its primary screen, you can get a quick read of key details: CPU temperature, load, and your cooler’s fan speed; your GPU’s temperature, load, and fan speed; and your RAM use. Easy stuff.
Assuming you’ve connected up your NZXT power supply correctly, you’ll also get a special section dedicated to power data. Click on the zappy lightning bolt icon, and you’ll see an updating measurement of how much juice your system is using, split into separate measurements for your CPU, your GPU, and any other devices connected to your power supply (hard drives and case fans, for example, which all get lumped together into an “others” category.)
You can’t adjust the little line chart to give you a bunch of historical data, or even an hour’s worth of measurements (alas), but you can click on the “Advanced” tab to examine the voltage and amps of your power supply’s rails. This is also where you can set up Over Current Protection, which can automatically shut down your system in the event of an unexpected short.
A separate section in the CAM software even allows you to adjust the profile of the power supply’s fan, in case it’s too loud while you’re trying to work. I set mine to the “quiet” default and never looked back, since my graphics card is the real noisemaker on my system anyway.
How accurate are a power supply’s readings?
I was pleased to find that the measurements from NZXT’s power supply and my aforementioned Belkin power meter were pretty close to one another. In my configuration, the power supply was underreporting by around 20w on average—likely the amount of power it draws for its fan and general operation, which it doesn’t count in its measurements.
(In case you’re curious, I tested this hypothesis by manually cranking the power supply’s fan to maximum. As I expected, the Belkin power meter’s reading shot up even more compared to the power supply’s reading. It returned back to the regular “20w overage” when I turned the power supply back to “quiet” mode.)
This presents an interesting trade-off. If you want a true, every-watt-counted measurement of how much power your desktop PC draws, a device like the Kill A Watt is your best bet. However, if you want a more detailed look at how much power your system’s components draw at any given time—or over time—a digital power supply is ideal. I’m going to stick with the latter… and just not look at that number, nor think about what it’s costing me, when I’m having an all-day gaming binge.