Power supplies matter more than they get credit for — an undersized PSU is one of the most common causes of an intermittent fault that looks like a camera, panel or lock problem but is actually a voltage problem. Choosing the right unit means matching current (amps), not just voltage, to what it is powering.

Sizing a power supply

• Add up the current draw of everything on the supply, then add at least 20% headroom — running a PSU at its rated maximum shortens its life and leaves nothing for a standby battery to charge.
• Match the voltage exactly. Most CCTV cameras run on 12V DC; most alarm panels and access control equipment run on 12V DC or occasionally 24V AC — check the device before ordering, not after.
• Boxed vs plug-in. A boxed PSU with a standby battery keeps a panel, lock or PoE switch running through a power cut and is standard on any commercial access control or alarm installation. A simple plug-in adapter is fine for a single low-draw device with no backup requirement.

Where these are used

PSUs here cover intruder alarm panels and expanders, access control locks and controllers, and CCTV camera and PoE equipment power. If you already know which system you are powering, the linked category has power supplies matched to that equipment and the compatible cable to go with it.