4, 8 or 16 channels: how to size a PoE NVR kit
Most buyers pick a channel count by guessing, then run out of ports six months later. The number that matters is not how many cameras you want today, but how many points of view the site needs to stay covered after a wall gets built.
Start from the views, not the cameras
A channel is one camera stream. Before counting cameras, walk the site and mark every place where something happens that nobody currently sees: the gate, the loading bay, the till, the aisle where stock walks out, the meter cupboard, the yard gate. Each of those is a view. One camera can cover two views only when they are close together and the lens is wide enough to keep both readable.
Retail shops usually land on 4 to 8 channels: entrance, till, two or three aisles, stockroom, back door. Warehouses and yards go to 8 or 16 because the perimeter alone can take six cameras before you get inside. A single-family house rarely needs more than 4.
| Site | Typical views | Channels to buy |
|---|---|---|
| Flat or small office | Entrance, corridor, back door | 4 |
| Shop with stockroom | Entrance, till, 2-3 aisles, stockroom, back door | 8 |
| Warehouse or workshop | 2 gates, 2 loading bays, 3-4 aisles, 2 perimeter | 16 |
| Yard or car park | 4 perimeter, 2 entrances, 1-2 internal | 8, plus 4 spare |
Leave two ports empty on purpose
Buy for today plus two spare ports. A 8-channel recorder with 6 cameras in use is cheaper than a 4-channel recorder replaced in a year, and the two free ports cover the camera somebody will ask for after the first incident. Spare ports cost less than a second recorder, a second power supply and a second site visit.
Match the PoE budget, not just the port count
A PoE recorder has a total power budget, printed on the data sheet, and each camera draws from it. Standard PoE gives up to 15.4 W per port, PoE+ up to 30 W. A fixed dome might pull 6 W; a PTZ with heaters can pull 25 W or more. Add the realistic draw of every camera, then check the recorder's budget with at least 20 percent headroom, because cold nights push heaters on and that is when a marginal budget fails.
- Add up camera draw at night, not at noon: IR and heaters are the peak.
- If the total is close to the recorder's budget, move the PTZ to its own injector.
- Long cable runs lose voltage: past roughly 80-100 m, check the camera still boots.
Resolution decides bandwidth and disk, not channels
Channel count and resolution are separate decisions. Four 4 MP cameras at 4 Mbps each is 16 Mbps and a very different disk bill from four 2 MP cameras at 2 Mbps. If you are unsure, buy the channel count you need and set resolution per view: higher on the gate where faces matter, lower on an aisle that only needs movement.
A kit is only as good as its weakest part. Check that the recorder's PoE budget covers the cameras in the box at their night draw, and that the switch inside the recorder supports the standard your cameras expect.
What to send when you ask for a quote
Send the site type, the number of views, whether any camera is a PTZ, the longest cable run, and the retention you need in days. With those four numbers a kit can be quoted with the right recorder, the right PoE budget and the right disk, instead of a box that fits the photo but not the site.
Updated 2026-10-22 ยท 3 min read. Specifications are revised without notice; confirm the current sheet before you publish a tender document.
Questions that come back
Short answers, before the email.
Can I add cameras later to a 4-channel kit?
Only up to four. The recorder has four channels and usually four PoE ports; a fifth camera needs a second recorder or a larger one. Buying two spare channels at the start is cheaper than replacing the recorder.
Do all cameras in a kit have to be the same model?
No. Any camera that speaks the recorder's protocol and fits its PoE budget can join. Mixing resolutions is normal: high resolution at the gate, standard resolution in a corridor.
What retention can I expect from a 1 TB disk?
Roughly 10 to 20 days for four 2 MP cameras at 2 Mbps, less if you raise bitrate or add channels. The recorder's storage calculator gives the exact figure once you fix resolution and bitrate.
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Where to go next
Send the site, get the sheet.
Model code, distance and destination market is enough to start.