Networking · March 2026 · 7 min read

What Is Power over Ethernet?

Power over Ethernet (PoE) is a technology that delivers both electrical power and network data over a single Ethernet cable. For CCTV installations, this means each IP camera needs just one cable run from the switch or NVR — no separate power supply, no mains socket needed at the camera location. It's the technology that made modern IP surveillance practical, and it's the standard we use on virtually every installation across Northern Ireland.

Before PoE, installing a camera meant running both a data cable and a power cable to each location, or using a local power adapter that needed a mains socket nearby. On a farm in County Tyrone with cameras mounted on barn walls, or a warehouse in Larne with cameras at ceiling height, finding mains power at each camera position was expensive and often impractical. PoE eliminated that problem entirely.

PoE Standards Explained

Not all PoE is created equal. The IEEE has defined several standards, each delivering different power levels:

802.3af (PoE) — The original standard, delivering up to 15.4W per port (12.95W at the device after cable losses). This is sufficient for most fixed IP cameras, including turrets and bullet cameras from Hikvision and Dahua. The vast majority of CCTV cameras we install across Belfast, Derry and the rest of NI operate comfortably within this power budget.

802.3at (PoE+) — Delivers up to 30W per port (25.5W at the device). Required for more power-hungry devices like PTZ (pan-tilt-zoom) cameras, cameras with built-in heaters for extreme cold, and some high-performance access points. We use PoE+ switches as standard because the cost difference is minimal and the flexibility is valuable.

802.3bt (PoE++) — The latest standard, delivering up to 60W or 90W per port depending on the type. This powers devices like high-speed PTZ cameras, LED lighting and digital signage. It's less common in standard CCTV installations but increasingly relevant for advanced security systems.

How PoE Simplifies Camera Installation

The practical benefits of PoE for CCTV installation are enormous. Consider a typical eight-camera system for a business premises in Armagh. Without PoE, you'd need eight data cable runs plus eight power cable runs, eight power adapters and potentially eight mains sockets installed by an electrician. With PoE, you run eight Ethernet cables from the switch to the cameras, plug them in, and you're done.

This simplicity translates directly into lower installation costs, faster completion times and fewer potential points of failure. Every power adapter is a potential failure point — they overheat, they get knocked out of sockets, they degrade over time. PoE eliminates all of them, with power delivered reliably from a centralised switch that can be protected by a UPS (uninterruptible power supply) in your network cabinet.

PoE Switches vs PoE Injectors

There are two ways to add PoE to a network. A PoE switch has PoE built into every port — plug in a camera and it receives power automatically. A PoE injector is a standalone device that adds power to a single Ethernet connection, sitting between a non-PoE switch and the camera.

For any installation with more than two cameras, a PoE switch is the clear choice. It's neater, more reliable and easier to manage. PoE injectors have their place — adding a single camera to an existing non-PoE network, for example — but for new installations across Northern Ireland, we always specify PoE switches. The TP-Link Omada managed PoE switches we use provide the added benefit of per-port power monitoring and remote management.

Cable Distance Limits

PoE operates within the standard Ethernet distance limit of 100 metres from switch to device. This is a hard limit — beyond 100 metres, both data and power delivery become unreliable. For most business premises in NI, 100 metres is more than adequate. A typical shop, office or warehouse can be covered comfortably within this distance.

For larger sites — farms with outbuildings, industrial estates or multi-building campuses — cable runs can exceed 100 metres. In these cases, we use PoE extenders (which regenerate both data and power signals) or install a secondary switch in an outbuilding. On agricultural sites across County Fermanagh and Tyrone, we've designed systems with weatherproof junction boxes housing PoE extenders to reach cameras on distant barns and field gates.

PoE Budget Calculations

Every PoE switch has a total power budget — the maximum amount of power it can deliver across all ports simultaneously. A switch with eight PoE ports and a 120W budget can theoretically power eight cameras at 15W each. In practice, you should plan for 80% utilisation to allow headroom for power spikes during camera boot-up or IR illuminator activation.

Getting this calculation wrong means cameras dropping offline when the switch can't deliver enough power. We see this regularly on DIY installations — someone buys a cheap 8-port PoE switch with a 65W budget, connects eight cameras that each draw 10W, and wonders why two cameras keep disconnecting. Proper PoE budget planning is part of every system we design.

Managed vs Unmanaged PoE Switches

Unmanaged PoE switches are plug-and-play — connect your cameras and they work. They're fine for very small, simple installations. Managed PoE switches add VLAN support, per-port power management, bandwidth control, remote monitoring and the ability to reboot individual camera ports remotely. For any professional CCTV installation, managed switches are worth the modest premium.

The ability to remotely power-cycle a frozen camera from your phone at midnight — rather than driving to a site in Cookstown in the rain — pays for the upgrade many times over.

Cable Choices: Cat5e, Cat6 and Cat6a

Cat5e — Supports gigabit Ethernet and PoE up to 100 metres. Perfectly adequate for most CCTV installations and the most cost-effective option. We use Cat5e for the majority of camera runs across Northern Ireland.

Cat6 — Offers better performance at shorter distances and improved shielding against interference. We recommend Cat6 for runs near electrical cables, in industrial environments or where future-proofing is a priority.

Cat6a — Supports 10-gigabit Ethernet and offers superior shielding. Overkill for most CCTV installations but worth considering for backbone connections between switches or in environments with significant electrical interference.

Regardless of category, always use solid-core cable for permanent installations (not stranded patch cable) and ensure it's from a reputable manufacturer. Cheap cable with substandard copper causes more CCTV problems than any other single factor.