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Most UK installers size a PoE switch by camera count alone—then wonder why systems reboot at night or lose IR footage when the budget runs dry. A PoE switch must deliver not just data but enough power to every camera simultaneously, accounting for cable loss over distance, and the maths is straightforward once you know the three numbers that matter: total wattage per camera, run length, and the switch's actual power budget. This guide gives you the exact calculation installers use to avoid undersizing, plus the real-world warning signs (flickering, reboots, IR dropout) that tell you a switch is too small for the job.

TL;DR

A PoE switch powers multiple IP cameras over a single cable run, but undersizing the power budget is the #1 reason cameras reboot or lose IR at night. This guide walks you through the exact maths installers need: port count, per-camera wattage, cable loss over distance, and the real-world troubleshooting signs that tell you a switch is too small.

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What Is a PoE Switch for CCTV?

A PoE (Power over Ethernet) switch delivers both data and electrical power to IP cameras through a single Cat5e or Cat6 cable, eliminating the need for separate 12V power supplies at each camera location. The switch sits between your NVR (network video recorder) and your cameras, centralising power management and simplifying installation.

In practice, the switch plugs into mains power, connects to your NVR via an uplink port, and each camera connects to one PoE port. The switch detects the camera's power demand and supplies up to 30W per port (IEEE 802.3at standard), or up to 95W in high-end PoE+ models. This single-cable approach cuts labour time on site and reduces clutter in cable trays or conduit, especially on multi-camera deployments where running separate power to a dozen locations would otherwise demand additional electrician hours.

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Sizing: How Many Ports and What Power Budget?

The first decision is port count vs. your camera count, plus 20% headroom for future expansion. An 8-port PoE switch for CCTV suits small sites (a shop, small warehouse); a 16-port handles mid-size deployments (office parks, car parks); a 24-port PoE switch for CCTV covers large estates. The Hikvision DS-3E0510P-E offers 8 Gigabit PoE ports at £69.90, whilst a 16-port Gigabit PoE switch with 150W budget costs £113.85 and a 24-port model reaches £179.00.

Power budget is the critical number — and it's where most undersizing happens. Each camera draws between 5W (passive fixed lens, no IR) and 15W (motorised zoom with infrared), so a 16-camera site with 10W average per camera needs 160W total. If your switch has only 120W budget, you're short 40W, and cameras will reboot or drop IR when the load peaks at night. Always add 25% headroom to the total: if cameras draw 160W, specify a 200W+ switch. Check the datasheet for the total power budget (not per-port), because a switch may advertise 30W per port but cap the overall supply at 150W.

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Cable Loss and Distance: The Hidden Drain

Power loss over long cable runs is real and often overlooked. A 100m Cat5e run to a distant camera can lose 2–4W, enough to drop a 12W camera below its operating threshold. The longer the cable, the thinner the gauge, the more voltage drops at the far end. IEEE 802.3at specifies a maximum of 100m per run, but in practice, anything beyond 60m should trigger a power-budget recalculation.

Use this rough guide: at 50m with Cat5e, assume 10% power loss; at 75m, assume 15%; beyond 100m, the standard fails. If a camera is 80m away and draws 12W, budget for 12W × 1.15 = 13.8W from the switch. For long runs, upgrade to Cat6 (lower resistance) or run a second power supply to that camera. Always measure your cable runs before ordering; a site plan with distances marked is worth an hour of troubleshooting later.

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Real-World Troubleshooting: Signs Your Switch Is Undersized

If cameras reboot at night or lose IR, your power budget is too tight. Infrared LEDs are the biggest power draw (5–8W per camera), so the problem appears when all cameras go to night mode simultaneously. Other signs include: cameras dropping off the network briefly during peak recording, video freezing when multiple cameras stream at full resolution, or a camera working fine for weeks then failing after firmware updates (which increase processing load).

To diagnose, check the NVR's event log for power-loss warnings, or use a PoE tester (£15–30) to measure voltage at the camera end — anything below 44V means cable loss or switch undersizing. The fix is either a larger switch, shorter cable runs, or adding a local PoE injector near the distant camera. Never daisy-chain switches to add ports; each link introduces latency and power loss.

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Choosing the Right Switch: Key Specs to Compare

Feature	8-Port	16-Port	24-Port
Typical Price (GBP)	£69.90	£113.85	£179.00
Power Budget	60–90W	150W	150W+
Uplink Ports	1 Gigabit RJ45	2 Gigabit RJ45	2 Gigabit RJ45
Best For	Small shops, 5–6 cameras	Mid-size sites, 10–14 cameras	Large estates, 18–22 cameras

Look for unmanaged switches (simpler, cheaper) unless you need VLAN isolation or traffic shaping. Managed switches add cost (£250+) and complexity; for most CCTV sites, an unmanaged Gigabit model with enough power budget and uplink redundancy is the right choice. Verify the switch supports IEEE 802.3af/at (standard PoE), check the total power budget on the datasheet (not marketing blurb), and confirm uplink port count — two uplinks let you loop back to the NVR for redundancy if one link fails.

Hikvision and UKVISION dominate UK CCTV supply chains; both offer reliable unmanaged models. Avoid Cisco PoE switches for CCTV unless you already run Cisco infrastructure — they're overkill for video and cost 3–4× more.

What Is a PoE Switch for CCTV?

A PoE (Power over Ethernet) switch delivers both data and electrical power to IP cameras through a single Cat5e or Cat6 cable, eliminating the need for separate power supplies at each camera location. This simplifies installation, reduces cable clutter, and cuts labour costs on site.

How PoE Works in CCTV Systems

A PoE switch sits between your IP cameras and your NVR (network video recorder) or management software, injecting power into the same twisted-pair lines that carry video and control data. The switch complies with IEEE 802.3af (up to 15.4 watts per port), IEEE 802.3at (up to 30 watts), or IEEE 802.3bt (up to 95 watts or higher), depending on the model and camera power demand. The standard you choose must match your camera's draw — a high-resolution PTZ or thermal camera may need 30 watts or more, while a basic fixed turret typically uses 5–10 watts.

PoE vs. Traditional Coax + Power

Traditional CCTV required two separate runs to each camera: coaxial cable for video and a mains-rated power cable (usually 2-core). This meant double the conduit space, two termination points per camera, and higher installation time. PoE consolidates this into one Gigabit Ethernet cable, which is thinner, cheaper to run, and easier to manage in retrofit or new-build projects. You still need to size your power budget — a 16-port switch with a 150-watt total budget can power roughly five to eight typical cameras, depending on their individual wattage.

Entry-Level and Scalable Options

For small installations (4–8 cameras), the Hikvision DS-3E0510P-E 8-Port Gigabit PoE Unmanaged Network Switch at £69.90 offers a straightforward, plug-and-play solution with 8 PoE ports and 1 Gigabit uplink to your NVR. For medium deployments, a 16-port switch like the UKVISION 16-Port Gigabit PoE Switch for CCTV at £113.85 provides 150 watts of total power budget and 2 uplink ports for redundancy or daisy-chaining. Larger sites (20+ cameras) benefit from a 24-port model such as the DS-3E0326P-E/M(B) at £179.00, which delivers approximately 8.8 Gbps switching capacity and stable performance across dozens of simultaneous streams.

Do You Need an NVR?

No — a PoE switch alone does not require an NVR. You can connect cameras directly to the switch and stream them to a PC running VMS (video management software) such as Hikvision iVMS, UniFi Protect, or third-party platforms like Milestone or Blue Iris. However, an NVR provides local storage, continuous recording, and a dedicated appliance that doesn't depend on a always-on server. Most professional installations pair the switch with an NVR for reliability and simplicity, but the switch itself is purely a network device — it powers and connects cameras; it does not record.

Choosing the Right Size

Match the port count to your camera count plus one or two spares for future growth. An 8-port switch suits 4–6 cameras; a 16-port handles 12–14; a 24-port accommodates 20+. Check the total power budget against your camera specs — if you have five 30-watt PTZ cameras, you need at least 150 watts available. Unmanaged switches (no configuration needed) are standard for CCTV; managed switches add VLAN and QoS control for complex networks but cost more and require IT knowledge.

Step 1: Count Your Cameras & Choose Port Count

Match the switch port count to your camera count, then add 20–30% headroom for future expansion or redundancy.

A common mistake is buying the smallest switch that fits your current setup. If you have six cameras, an 8-port switch looks tempting at £69.90, but you'll have no room to add a seventh camera, a backup feed, or a second NVR connection without replacing the entire switch. The rule is simple: count your cameras, then buy the next size up. This costs little extra upfront and saves you a reinstall later.

Understanding PoE Ports vs. Uplink Ports

Every PoE switch for CCTV has two types of port. PoE ports power your IP cameras directly—each port delivers both data and power over a single Ethernet cable. Uplink ports connect to your NVR, router, or network backbone; they carry data only and do not supply power to cameras. The UKVISION 16-Port Gigabit PoE Switch for CCTV has 16 PoE ports plus 2 Gigabit uplink ports, for example. This separation matters: if you miscalculate and treat an uplink port as a camera port, you'll lose power to a camera and wonder why it goes dark.

Sizing Guide: Port Count by Camera Load

Camera Count	Recommended Switch	PoE Ports	Uplink Ports	UK Price
1–6 cameras	8-port	8	1	£69.90
8–14 cameras	16-port	16	2	£113.85
15–22 cameras	24-port	24	2	£179.00

For a 10-camera system, a 16-port switch gives you 6 spare PoE ports for growth and one uplink to your NVR, with a second uplink for redundancy or a second recorder. The 24-Port Gigabit PoE Switch | 150W Budget at £179 suits larger installations—think retail chains, car parks, or multi-building sites where you want headroom without daisy-chaining switches.

Why You Can't Just Buy the Smallest Switch

Undersizing forces you to choose between three bad outcomes: daisy-chain switches (adds latency and complexity), replace the switch later (labour cost and downtime), or stop expanding (lose future business or security coverage). A 16-port switch costs only £14 more than an 8-port; a 24-port is just £65 more than the 8-port. The insurance against future retrofit is cheaper than the retrofit itself.

Step 2: Calculate Total PoE Budget (The Critical Maths)

Add up the wattage draw of every camera you plan to connect; the switch's total PoE budget must exceed this sum by at least 20% to avoid brownouts and port shutdowns.

Most installers buy a PoE switch for CCTV by counting ports, not watts — and that's where systems fail. A 16-port switch doesn't mean you can run 16 cameras if each pulls 15W; you need to know the switch's total power budget and each camera's actual draw under load (especially with infrared active).

IEEE Standards: What Your Switch Can Supply

The PoE standard your switch supports sets the ceiling for per-port power.

• IEEE 802.3af: 15.4W maximum per port (older, rarely used for modern CCTV).
• IEEE 802.3at (PoE+): 30W per port; the standard for most turret and dome cameras.
• IEEE 802.3bt (PoE++): 60W+ per port; needed for high-end PTZ and multi-sensor units.

The 16-Port Gigabit PoE Switch with 150W Budget delivers 30W per port maximum and a total budget of 150W — meaning all 16 ports combined cannot exceed 150W, even if each port is rated for 30W individually. That's the trap: per-port rating ≠ total budget.

Typical Camera Power Draws

Real-world wattage varies by camera type and operating mode.

Camera Type	Typical Draw	Notes
Turret (fixed, no IR)	5–8W	Day mode only
Dome (fixed, no IR)	6–12W	Includes heater/cooler
PTZ (pan-tilt-zoom)	30–50W	Stepper motors draw heavy current
IR turret (night mode)	8–15W	IR LEDs add 3–8W to base draw
Thermal/multi-sensor	15–25W	High-end imaging

The hidden cost of infrared: many installers forget that IR adds 3–8W to a camera's draw. An 8W turret becomes 12–15W at night, and if you've budgeted for 8W across 16 cameras, you'll trigger port shutdowns when dusk falls.

Worked Example: 12 Cameras, 8W Each

Assume you're installing 12 fixed turret cameras, each rated 8W in daylight, 12W with IR active at night.

• Minimum budget (day mode): 12 × 8W = 96W
• Real-world budget (night mode): 12 × 12W = 144W
• Safe choice: a switch with ≥180W total budget (144W + 25% headroom)

The 16-Port Gigabit PoE Switch with 150W Budget supplies exactly 150W total. In this scenario, it meets the daytime load (96W) but falls short at night (144W). You'd need the 24-Port Gigabit PoE Switch | 150W Budget | UKVISION — also 150W — or a higher-capacity model.

The rule is simple: calculate worst-case draw (IR on, all cameras active), add 20%, then choose the switch.

Why Port Count Misleads

A 24-port PoE switch for CCTV sounds like it handles 24 cameras, but if the budget is only 150W, you're limited to roughly 12 cameras at 12W each. Conversely, an 8-port switch with a 120W budget can run 10 low-power cameras if you add an uplink port.

The answer to "how many cameras per PoE switch?" is always: it depends on wattage, not port count. Check the datasheet's total power budget first; port count is secondary.

Building Your Worksheet

1. List every camera model and its rated draw (check the spec sheet; manufacturers often list PoE power separately from total power).
2. Add 20–30% for IR, heater/cooler, or future upgrades.
3. Compare the total to the switch's total PoE budget, not the per-port rating.
4. If the switch's budget is borderline, choose the next size up — undersizing is the most common cause of intermittent camera dropout and support calls.

The Hikvision DS-3E0510P-E 8-Port Gigabit PoE Unmanaged Network Switch at £69.90 is affordable for small sites (4–6 cameras), but verify its total budget against your camera list before committing. A 16-port or 24-port switch is often better value if you're adding cameras later.

Step 3: Account for Cable Loss Over Distance

Power delivery drops roughly 3% per 50 m of Cat5e or Cat6 cable; cameras beyond 80 m from the switch may reboot or lose PoE entirely unless you upgrade to PoE+ (802.3at, 30W per port) or add a midspan injector at the camera end.

Why 100 m Ethernet Doesn't Equal 100 m PoE

The Ethernet standard guarantees data transmission to 100 m, but PoE is a voltage-dependent power delivery system — voltage drops as current travels down the cable, and that loss is cumulative. A standard 802.3af PoE source delivers 15.4W at the switch; by 80 m over Cat5e, the camera may receive only 12W due to resistive loss in the copper. If your camera draws 10W for the sensor and lens motor, plus 3W for infrared illumination, it starves at 12W and either reboots or shuts down the IR entirely.

The Installer's Rule of Thumb

Distance	Standard (802.3af)	Recommendation
≤50 m	Safe	Use 802.3af (15.4W); monitor in summer
50–80 m	Marginal	Monitor power draw; consider PoE+ if IR or PTZ
>80 m	Unsafe	Upgrade to PoE+ (30W) or add midspan injector

For runs under 50 m, standard 802.3af is reliable. Between 50–80 m, watch the camera's actual power consumption — many fixed 4 MP turrets draw 5–8W and will work, but thermal or IR-heavy models may struggle. Beyond 80 m, you must either switch to PoE+ or install a PoE injector at the camera end to restore voltage.

Real-World Scenario: The 70 m Starving Camera

A 2 MP dome camera 70 m away on Cat5e, powered by 802.3af, receives roughly 12W instead of 15.4W. If the camera's processor draws 4W, the lens motor 3W, and the IR array 5W, you're asking 12W to deliver 12W — no headroom for surge or thermal margin. In summer, or when the IR triggers, the camera reboots. Swapping to a PoE+ switch with 30W per port delivers 24–26W at 70 m, solving the problem instantly.

Practical Fixes: PoE+ or Midspan Injection

PoE+ (802.3at) switches cost 15–20% more than 802.3af but deliver 30W per port, making them safe for runs up to 100 m with most standard cameras. A 16-port PoE+ switch with 150W total budget runs around £100–£115 and handles longer cable runs without compromise.

Midspan injectors are cheaper (£20–£40 each) but require a separate device at the camera location — useful for retrofitting a single long run, but awkward if you have multiple distant cameras. Install the injector in a weatherproof box near the camera, feed the Ethernet from your switch into it, and the injector re-powers the line to the camera.

Use Cat6 instead of Cat5e if you're running 60+ m; Cat6 has slightly lower resistance and reduces voltage drop by 5–10%, buying you margin without upgrading the switch.

Recommended kit

For the setup above, this is the kit we'd fit from our own range:

• UKVISION 16-Port Gigabit PoE Switch for CCTV — UKVISION 16-port Gigabit PoE switch powers IP CCTV cameras and links to NVRs via 2 Gigabit uplink ports, with 36 Gbps capacity and unmanaged setup, £113.85.
• 24-Port Gigabit PoE Switch | 150W Budget | UKVISION — 24-port gigabit PoE+ switch with 150W total power budget, 30W per port, 2 uplink ports. IEEE 802.3af/at compliant, extend mode to 250m, rack-mountable.
• 16-Port Gigabit PoE Switch with 150W Budget — UKVISION 16-port unmanaged Gigabit PoE switch for CCTV and network installations. 150W total budget, 30W per port, 2 uplink ports, 250m extend mode.
• Hikvision DS-3E0510P-E 8-Port Gigabit PoE Unmanaged Network Switch — • 8 × Gigabit PoE Ethernet ports • 1 × Gigabit RJ45 uplink port • 1 × Gigabit SFP fiber uplink port • Supports IEEE 802.3af and IEEE 802.3at PoE standards • Maximum 30 W output per PoE port • Tot