Power is the part of a CCTV job that most installers get right on smaller sites — and the part that quietly causes the most call-backs on larger ones. Whether you're running eight cameras across a commercial unit or speccing out a 16-camera system across multiple buildings, getting the power spec wrong leads to dropped feeds, nuisance resets, and customers ringing you at 11pm wondering why half their cameras are offline.

This guide walks through the practical side of speccing stable power for multi-camera jobs — the things worth thinking through before you're standing on-site with a half-finished install.

Why power is the first thing to get right

It's easy to focus on the cameras, the recorder, and the cabling — but if the power supply isn't properly specced, none of that kit performs the way it should.

Under-rated PSUs are one of the most common sources of nuisance faults in CCTV systems. A camera drawing 1.5A that's being fed from a supply already near its maximum will work fine most of the time — until a cold night causes the IR cut filter to activate, or the camera wakes up after a reboot and draws a brief inrush surge. That's when you see a camera drop off the NVR for no obvious reason and come back a few minutes later, apparently for no cause at all.

The same logic applies when you're speccing out IP CCTV cameras for a job. Know the power draw of each unit before you finalise your power spec — don't rely on assumptions.

Calculating your total load — don't cut corners here

The first step is straightforward: add up the current draw for every device on the circuit.

Most cameras will be rated in watts or amps. If a camera is rated at 7W, divide by the supply voltage (12V for standard DC cameras) to get amps — 7W ÷ 12V = approximately 0.58A. Do this for every device on the same supply and add them up.

From there, spec a power supply with at least 25% headroom above your calculated load. So if your cameras total 8A, don't spec an 8A supply — go for a 10A or 12A unit. This gives you room for inrush current on startup, any additional kit you might add later, and the variance you get between a camera's rated draw and what it actually pulls in real conditions.

If you're sourcing from a reliable CCTV equipment supplier, they should be able to help you cross-reference current draw against the right power supply for the job.

Central PSU vs individual camera power supplies — what's the right call?

On smaller jobs, running individual plug-top PSUs to each camera is common and often perfectly fine. But once you're running more than four or five cameras, it's usually better practice to use a central multi-output power supply, ideally one with individually fused outputs.

A fused output board means that if one camera develops a fault or a short, it trips its own fuse rather than taking the whole distribution board down. That's a meaningful difference when a customer has 16 cameras running and half of them share a supply.

You can browse a range of power supplies for CCTV installations — including multi-output and fused distribution options — that are built with installers in mind. Having individually labelled, fused outputs also makes fault-finding significantly quicker on return visits.

Voltage drop on long cable runs

This is a surprisingly common problem that doesn't always get caught until commissioning — or worse, a few weeks later when the customer calls with intermittent issues.

Every metre of cable has resistance. Over a long run of 50 metres or more, the voltage arriving at the camera end can drop meaningfully below the 12V it started at. If a camera requires a minimum of 10.5V to operate reliably, you don't have much margin before you're in nuisance fault territory.

The practical fixes are:

• Use a heavier gauge cable on longer runs (1mm or 1.5mm rather than the standard 0.75mm)

• Supply power at 13.5V to compensate for the expected drop

• Switch to PoE for distant cameras, where power is delivered over Cat5e/6 and is better regulated

If you're using PoE, make sure you've thought through your PoE budget carefully — both at the switch and the NVR end. Our detailed guides on PoE power budgeting for IP CCTV — part 1 and part 2 are worth working through before you finalise a larger spec.

PoE switches: when to spec a dedicated unit vs relying on NVR ports

Many IP CCTV NVRs — including those in our NVRs range — come with built-in PoE ports, and for smaller jobs those ports are convenient and perfectly capable. But on larger jobs, built-in NVR PoE has limits both in total wattage budget and in the fact that it ties your camera connectivity directly to the recorder.

Using a dedicated PoE switch separates the two functions and gives you more control. If the NVR needs rebooting, your cameras stay up. You can also position switches closer to camera clusters across a large site, reducing individual cable run lengths.

Just be careful with total wattage ratings. A common mistake is buying a 16-port PoE switch rated at 150W total and assuming that means 150W per port — it doesn't. That 150W is shared across all active ports simultaneously.

Fusing and circuit protection

Whether you're using a central PSU or individual supplies, circuit protection should be part of your spec from the outset.

Individual fuses per camera output are standard on quality multi-output distribution units. If you're building your own distribution, match the fuse rating to the cable capacity and the load — don't put a 10A fuse on a circuit where the camera draws 0.5A and the cable is rated for 3A.

For the mains side, make sure any CCTV power equipment is fed from a correctly rated MCB in the consumer unit. On outdoor installations or commercial sites, also consider surge protection — a £25,000 CCTV installation taken down by a mains spike is not a conversation you want to be having.

Check out our article on connectors and terminations for more on the smaller details that cause big faults weeks after commissioning.

Cable selection matters too

Cable choice affects power delivery as well as signal quality. For anything requiring connectors and terminations, make sure you're using quality parts throughout. It's one of the areas where saving a few pence per termination ends up costing you more in revisit time.

You can browse a full range of connectors and installation tools to make sure you're well stocked before arriving on-site.

If you're working on hybrid systems or takeover jobs that involve existing analogue cabling, it's also worth understanding when CAT5 transmission and baluns are the right solution — including whether they're appropriate for the power side of the job.

As a dedicated IP CCTV supplier, FVS CCTV stocks everything you need to keep a large install on a single account — cameras, recorders, switches, cabling, connectors, and power all in one place.

Pre-sign-off checklist for power

Before you sign off a job, it's worth working through these:

• Check each camera's current draw has been accounted for in the PSU spec — don't rely on guesswork or rated minimums

• Verify voltage at the camera end on any run over 30 metres, using a multimeter before commissioning

• Confirm your PoE switch or NVR wattage total, not just port count

• Test each fuse on a multi-output unit by confirming each output is live

• Check cable runs for any joins or damage, particularly on pre-existing cabling

• Label your PSU outputs — five minutes now saves thirty minutes on any future call-back

It's also worth staying current on what's changing in CCTV specs and compliance so your power and cabling approach is in line with current expectations on commercial jobs.

A note on sourcing accessories for larger jobs

One of the things that slows down larger installs is sourcing components from different suppliers and waiting on multiple deliveries. Using a dedicated CCTV accessories supplier for your power distribution, cabling, connectors, and sundries — the same one you use for cameras and recorders — keeps your pricing consistent and means one call resolves any issues.

FVS CCTV supplies trade installers across the UK with everything needed to complete a job, from cameras and recorders down to the connectors and cable clips.

FAQs

Q: How much headroom should I leave on a CCTV power supply? A: As a general rule, spec at least 25% above your calculated total load. If several cameras power up simultaneously, consider 30–40% headroom to account for inrush current at startup.

Q: Can I mix PoE cameras and 12V DC cameras on the same job? A: Yes — many installers do this. Just account for each type separately. PoE power budget is managed at the switch, while DC load is managed at the PSU. Don't conflate the two in your calculations.

Q: How do I diagnose a voltage drop problem on a long run? A: Measure the voltage at the camera with a multimeter under normal operating conditions. Below 11V on a 12V DC system is a red flag. Heavier gauge cable, a higher supply voltage, or switching to PoE will resolve it.

Q: What's the advantage of a fused multi-output PSU over individual plug-top supplies? A: Individual fused outputs mean a fault on one camera won't pull down others on the same supply. Fault-finding is faster, the install is neater, and there's one enclosure to deal with rather than a row of plug-tops competing for sockets.

Q: Is PoE always better than DC power for IP cameras? A: Not always. PoE is very convenient for most jobs, but you need to manage the total wattage budget carefully on larger systems. On very long cable runs beyond 80–90 metres, PoE can also struggle unless you use mid-span injectors or additional switches.

Q: Are there any UK regulations that affect how I power a commercial CCTV installation? A: The electrical side of the install must comply with BS 7671 (the IET Wiring Regulations). Any mains connections should be carried out by, or in conjunction with, a qualified electrician. The CCTV-specific side of compliance is covered by relevant British Standards and the ICO Code of Practice.

Ready to spec your next job?

If you're putting together a multi-camera system and want to make sure your power spec holds up, browse the full range of power supplies and accessories at FVS CCTV. We supply trade installers across the UK with everything from fused distribution units and PoE switches through to cabling and connectors.

To complete your full spec, take a look at our IP CCTV product range and NVR options. For trade pricing or technical help with a specific job, call us on 0208 863 0666 or get in touch online.