When upgrading or adding any device to your computer system, it is essential to know how much power the device requires from your computer's internal power supply. Adding a device to your computer that draws more wattage from your power supply than it is rated for can lead to an unstable system and possible damage to your internal components.
Checking Wattage Without Removing the Power Supply
Step
Unplug your case from any electrical source and press the power button for 10 seconds to ensure any stored electrical charge is dissipated.
Step
Remove the thumbscrews from the rear face of the case that hold the computer's side access panel in place, and pull the side access panel back with light force to remove it from the case.
Step
Locate your power supply within your case. It will be located against the rear wall of the case, either at the very top or the very bottom.
Step
Look at the exposed faces of the power supply unit for a sticker or label that describes the unit's electrical capacities. This label is required to be placed on all ATX form factor computer power supplies. It will designate how many amps are available for each voltage type and give a "watts max" designation. For example, a 300-watt power supply would read "300 watts max." This maximum wattage is your power supply's wattage rating.
Step
Replace you computer's side case panel and securely tighten the thumbscrews back into place.
Step
Plug your computer back into any previously disconnected electrical sources.
Checking Your Power Supply's Wattage if the Label is Obscured
Step
Continue from Step 5 of the previous section if you cannot readily see the power supply's rating label due to its placement on an inward-facing side.
Step
Remove the detachable power cord that runs from the power supply to your electrical outlet. This cord simply pulls out of the back of your computer and is easily reattached.
Step
Locate the four mounting screws on the back side of the power supply. These screws are on the same side the power cord was removing from in the last step. Remove the four screws and set them aside taking care not to lose them.
Step
Use light force to slide your power supply forward toward the front of your case where your hard drives and optical drives are located.
Step
Pull your now semi-free power supply outward away from the case. Take care not to pull too hard or fast, because all your components are still connected to your power supply.
Step
Manipulate the drive and check every face for a specifications label. Once you find it, check the wattage rating as explained in step 5 of the previous section.
Step
Reposition your power supply into its original position, and remount it with the four mounting screws you removed earlier.
Step
Replace the female plug removed earlier from the rear of the power supply back into place.
Step
Reassemble the case as detailed in steps 6 and 7 of the previous section.
