Last updated: June 2026
Every IP camera spec sheet says the same thing: supports PoE up to 100 metres. Every installer knows the truth: many cameras fail well before 100 metres, especially outdoor cameras with heaters, IR arrays, and pan-tilt motors. The 100-metre number is not a guarantee. It is a best-case theoretical maximum calculated under ideal conditions that almost never exist in the real world.
Where the 100-Metre Number Comes From
IEEE 802.3 specifies 100 metres as the maximum segment length for 100BASE-TX and 1000BASE-T Ethernet. This limit is based on round-trip signal propagation delay, not power delivery. The 100-metre standard was established decades before PoE existed. PoE inherited this limit and operates within it — but power delivery often becomes the binding constraint long before signal integrity degrades.
The IEEE standard assumes: 24 AWG solid copper cable, ambient temperature of 20 degrees Celsius, and a device drawing base PoE power (12.95W). Change any of these variables and the usable distance shrinks.
The Real-World Derating Factors
Three factors reduce your actual usable distance. Temperature: cable resistance increases by 0.4% per degree Celsius above 20 degrees. A cable run through a UK loft at 50 degrees Celsius in summer has 12% higher resistance than the lab test. Power draw: an outdoor PTZ camera with heater, IR, and motor can draw 40-50W at peak. At 0.8A load, voltage drop is four times higher than at 0.25A. Cable quality: CCA (copper-clad aluminium) cable has 40% higher resistance than pure copper. Many budget installations use CCA cables without the installer realising.
Combined, these factors can reduce your effective distance from 100 metres to 50-70 metres for high-power outdoor cameras.
How to Design Runs That Actually Work
Use this practical derating table for outdoor camera installations in the UK: - Basic fixed camera, indoor: 100m (Cat5e solid copper) - Outdoor bullet with IR, mild climate: 80m - Outdoor bullet with IR and heater, UK winter: 60m - PTZ camera with full features: 50m - Multi-sensor camera: 40m
These distances assume 23 AWG Cat6 solid copper. Reduce by 20% for Cat5e (24 AWG). Reduce by 40% for CCA cable.
The Practical Fixes for Existing Installations
If your camera is already installed at 75 metres and fails under load, you have three options without re-running cable. Option 1: Install a midspan PoE injector at the 40-metre point. This regenerates the power signal. Option 2: Upgrade to 4-pair PoE (802.3bt) if both camera and switch support it. Option 3: Replace the camera with a lower-power model. Some newer cameras use efficient sensors that draw under 8W even with IR.
Video: Ring Outdoor Cam Pro Finally 4K! Test and (Honest) Review — a practical walkthrough of the technology discussed in this guide.
Frequently Asked Questions
1. Will a higher-quality cable extend my PoE distance?
Answer: Yes. Upgrading from Cat5e (24 AWG) to Cat6A (22 AWG or 23 AWG) reduces resistance by approximately 20-25%. This translates to roughly 15-20 additional metres of usable distance at the same power level. For more detail, see How to maintain Pubs, Bars and Restaurants CCTV systems - UK guide 2026. Also read our related guide: Why Your CCTV Camera Attracts Every Moth in the Neighbourhood: The Infrared Insect Magnet Problem. Browse our security technology hub at Uni Blog Security Hub. Official UK guidance on this topic: Surrey Security Centre.
2. Does PoE++ (802.3bt) automatically mean I can go further?
Answer: No. PoE++ delivers more power (up to 90W) but the current is higher, which means voltage drop is worse at the same distance. PoE++ is designed for high-power devices at shorter distances, not longer distances at the same power. For more detail, see Offices and Commercial Buildings. Also read our related guide: Why Your Neighbour's Ring Doorbell Is Legally Filming You: The Fairhurst v Woodard Rule Every UK Homeowner Misses.
3. Can I use a passive PoE injector instead of a standard switch to extend distance?
Answer: Passive PoE often uses 24V instead of 48V. Lower voltage means higher current for the same power, which means worse voltage drop. Passive PoE is generally not recommended for long cable runs. For more detail, see How to maintain Farms and Agricultural Property CCTV systems - UK guide 2026. Also read our related guide: BNC Connector Rot: The Single Most Common Failure Point in Analogue CCTV and Why It Always Fails at 2 AM.
4. Does using a managed PoE switch help diagnose distance problems?
Answer: Yes. Managed switches report per-port power consumption and voltage. If the switch reports a 'power denied' or 'overload' condition on a port, you have a voltage drop issue. Some managed switches also allow you to increase the PSE voltage to 57V maximum. For more detail, see Farms and Agricultural Property CCTV - UK legal requirements and GDPR compliance 2026. Also read our related guide: Why Your CCTV System Eats Hard Drives: The Surveillance-Grade vs Desktop Drive Truth.
5. How do I measure the actual voltage at the far end of a PoE run?
Answer: Use a PoE voltage tester (about GBP 30-50) that simulates a powered device. These testers report the actual voltage available at the far end under load. A multimeter alone cannot measure PoE voltage accurately because it does not draw current. Also read our related guide: Why Rural CCTV Cameras Die Faster: The True Cost of UK Countryside Installation Nobody Advertises.
Conclusion
The difference between a security system that works and one that frustrates is understanding the real-world behaviour of cameras, cables, and the environment they operate in. Manufacturers sell specifications. Installers solve problems. The questions above represent the issues that UK homeowners and businesses actually face — the ones the spec sheets do not mention.
Article by Gary Pearce, qualified security systems engineer. For a free security assessment, visit gary-pearce-home-services.pages.dev. This guide was last updated June 2026. Verify current UK regulations with the ICO.