How to measure your PC’s power use, and why it matters

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PCs are powerful machines. These boxes most of us have sitting on our desks or laps are capable of some incredible things. From intense A/V editing and rendering 3D images, to storing massive amounts of data, PCs and laptops are technological marvels. But being capable of such feats of computing begs the question: how much power do these things use? Furthermore, how does one go about measuring the power draw of their computer? We’ve got a quick solution for you, and we’ll discuss when and why it’s important to know just how much juice that box is drinking.

How to Measure

If, for whatever reason, you find yourself needing to know just how much power your PC or laptop is sucking out of your wall, the process is relatively simple, but it will require some extra hardware and tooling around with software.

First, you’ll want to download the free Microsoft utility, Jouleometer, to serve as your power calculator. This program installs quickly, and is simple to use. It works on laptops without any additional hardware.

If you’re testing for a desktop PC, you will need to get your hands on an external power meter, like a WattsUp? PRO device. These are available from the Watts Up? website for anywhere from $95 to $235. A power meter device will enable accurate measurements of your PC’s power draw, and Jouleometer will also be able to give you a more detailed breakdown of what components and applications are the most power-hungry if you are using a WattPro in conjunction with the application.

There are two ways you can use the WattsUp? PRO: either with your monitor plugged in, or not. When stating up Joulemeter, under the Calibration tab, select either “WattsUp PRO (Monitor(s) not on WattsUp)” if your monitor is not plugged into the WattsUp? PRO, or “WattsUp PRO (Laptop or Monitor(s) also on WattsUp)” if your monitor is plugged into the WattsUp? PRO. Unplug any USB disc drives, and then click on “Perform Calibration.”

For the next few minutes, your computer will power cycle a few times while the WattsUp? PRO takes its readings. After, you will be able to get a readout of your system’s power usage by component, in watts, under the Power Usage tab.

Joulemeter Power Usage Display

If you opt not to use an external power meter, Jouleometer has a “Manual Input Mode” that will give you decent estimations, but you will need to know approximately how much power is used by your system at different work loads, or use one of the presets provided by Joulemeter.

Joulemeter Manuel Model Entry

If you’re testing a laptop, you most likely wont need an external power meter, as Joulemeter is able to calculate a laptop’s power usage without one. You’ll need to make sure the laptop’s battery is charged to above 50 percent, then unplug the charging cable. Under the Calibration tab in Joulemeter, select “Running on Battery” from the drop-down menu, and run the calibration. After its complete, your wattage use will be displayed under the Power Usage tab.

Now, if you were to tally up the wattage use listed by the manufacturers for each of the components in your desktop, you might find that that such a number doesn’t add up to your readings from Jouleometer and your external gauge. This is largely due to your power supply. Power supplies pull more power than what is needed, as a chunk of it is lost as heat and noise.

Does it Matter?

Perhaps you’re wondering about your rig’s power draw merely out of curiosity, but there are some important reasons as to why you’d want to know the kind of wattage your system is using. The biggest reason you may want to know your PC’s power usage is for upgrades. Certain pieces of hardware, such as a new video card, will require a beefy power supply. Before you go out and purchase that brand new, several-hundred-dollars-worth video card, make sure you don’t need to upgrade your power supply as well. Furthermore, if it turns out you do need to upgrade your power supply, knowing how much the increase in electricity use will affect other components in your PC, and even the circuitry of your home, is important.

Of course, any upgrades you make to your PC are going to result in a change in power draw. If you’re slotting in bigger, badder components to ratchet up your gaming performance or rendering capabilities, your PC will need more power. That will likely translate to changes in your power bill. While a modestly built PC or laptop shouldn’t make a major difference to your monthly spending, a monstrous gaming rig probably will. More power will also result in more heat and more noise, as your system’s fans will kick on to prevent overheating. If for some reason heat or noise are of concerns, this may be another reason to keep track of your PC’s power use.

So if you’re making massive upgrades and looking to prevent errors or failures, or you’re pinching pennies on your power bill, tracking your PC’s power usage is going to help you out.


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