Worked Example: 8-Camera Small-Retail Security + Access Control
A single small-retail storefront, end to end: size the surveillance storage, size the uplink bandwidth the cameras need, size the battery backup that carries the system through an outage, then check that the home-run cables fit the conduit. One project, four calculators — the catalog working as a system.
- Cameras
- 8
- Storage
- 1.59 TB
- Bandwidth
- 16.4 Mbps
- UPS runtime
- 19 min
Step 1 — Size the surveillance storage
Start at Layer 9 (security). The storefront runs 8 cameras at 4 MP under the H.265 codec, kept for 30 days of retention. Working those numbers through the camera-storage model — bitrate per camera, motion factor, seconds per day, and the retention window — lands at roughly 1.59 TB of recording capacity for the whole system. Round up for the NVR overhead and headroom when you spec the drives.
Step 2 — Size the uplink bandwidth
Move to Layer 6 (networking). The same 8 cameras at 4 MP / H.265 each push a sustained stream; aggregated, the system draws about 16.4 Mbps of continuous video to the recorder and out to the network. A single 1 GbE uplink carries that with enormous margin — the point of sizing it is to confirm the switch and uplink are not the bottleneck, and to leave room for the access-control traffic on the same fabric.
Step 3 — Size the battery backup runtime
Now Layer 3 (power). Roll up the security-system load: 8 PoE cameras (about 6 W each, 48 W), the NVR (about 50 W), the access-control panel and door hardware (about 30 W), and the PoE switch (about 52 W) — 180 W total. Feed that 180 W load into the UPS-runtime model against the installed UPS — a 1000 W line-interactive unit on an 8 Ah / 24 V SLA string (two 12 V batteries in series) — and you get about 19 minutes of runtime: enough to ride through a short outage or trigger a graceful shutdown, but not an all-night hold. The calculator opens already populated with the full UPS scenario — the 180 W load, the 1000 W rating, and the 8 Ah / 24 V battery — so it reproduces the same 19 minutes.
Step 4 — Check the conduit fill
Finally, Layer 2 (conduit & cable tray). All 8 cameras home-run Cat6 drops back to the IDF. Eight Cat6 cables in a 1-1/4 in EMT run come to about 26.2% fill — comfortably under the 40% limit the NEC Chapter 9 tables allow for three-or-more conductors, so the run is code-compliant with room to add a spare. Drop to a 1 in EMT and the same 8 cables tip over 40% — which is exactly the kind of catch the conduit-fill calculator surfaces before the install, not after.
Every figure in this example is reconciled against the live calculators: 8 cameras → 1.59 TB of storage, 16.4 Mbps aggregate on a 1 GbE uplink, a 180 W load holding about 19 min on the UPS, and 8 Cat6 drops at 26.2% fill in 1-1/4 in EMT. Open any step in its calculator to change the inputs.