Why one cable does two jobs, and the switch trap that could leave your cameras dead.
Hardware prices verified 16 July 2026. Ubiquiti pricing changes — we confirm current pricing on every quote. Prices are indicative CAD, all-in. Contact AVNFi for a current quote.
Why PoE matters
Look at a security camera under an eave. It needs data, and it needs electricity.
Without PoE, that’s two trades and two cables — an electrician for a weatherproof outlet, and a network cable. Multiply by six cameras.
PoE (Power over Ethernet) sends both down one network cable. One cable, one trade, one hole. The camera has no power cord and no plug. Neither does the Wi-Fi access point on your ceiling, or the reader beside your door.
Which means the switch is doing something a power bar can’t. It’s the thing supplying the electricity. Every camera, every access point, every door reader in the building is drinking from it.
The rule: if it’s a camera, an access point, or a door reader — it needs a PoE port on a switch, and that switch needs enough power left in the tank.
PoE standards in plain English
There are tiers. A bigger device needs a bigger tier, and a device given too small a tier simply won’t come on. Not “runs slowly” — doesn’t work.
| Tier | Official name | Per port | What needs it |
|---|---|---|---|
| PoE | 802.3af | 15.4W | G6 Turret (12.5W), G6 Bullet (9.9W), G6 Dome (9.25W), U7 Lite AP (13W), door readers (5–6W) |
| PoE+ | 802.3at | 30W (32W on some switches) | Most Wi-Fi 7 APs — U7 Pro (21W), U7 Pro Max (25W). G6 180 (15W), G6 Pro 360 (13.5W), AI Turret (20W) |
| PoE++ | 802.3bt | 64W | Door hubs (UA-Hub-Door, 50W), E7 AP (43W), AI MS-4 (34.6W), AI PTZ (51W) |
| PoE+++ | Ubiquiti’s top tier | Not published in our data | The 10G ports on XG-series switches. We won’t quote a wattage we can’t source. |
Per-port figures verified from the USW-Pro-24-PoE spec: “PoE 15.4W; PoE+ 30W; PoE++ 64W”. The Flex 2.5G lists PoE+ as 32W — the tiers vary slightly by switch, so check the switch, not the standard.
How to use this: find your device’s wattage, then buy a port one tier above it. A 21W access point needs PoE+ — a 15.4W PoE port will not run it. And a 50W door hub needs a PoE++ port, which many small switches simply don’t have at all.
⚠️ The 210W trap — read this before you buy a USW-Ultra
This is the single most misleading number in the UniFi switch range, and it’s not Ubiquiti’s fault — it’s how the number gets repeated.
The USW-Ultra-210W is sold with “210W” in its actual product name. You would reasonably assume it has a 210W PoE budget.
It depends entirely on how you power the switch. Verified, straight from the spec sheet:
| How the switch is powered | PoE budget you actually get |
|---|---|
| 210W AC adapter (included with the USW-Ultra-210W) | 202W |
| 60W AC adapter | 52W |
| 60W PoE adapter | 42W |
| PoE++ input (fed from another switch) | 42W ⚠️ |
| PoE+ input (fed from another switch) | 16W ⚠️ |
Read that last row again. 16 watts. That is one camera, and only if you pick a small one. The exact same switch. The exact same product page. A 12× difference decided by nothing but what you plugged into the back.
Why anyone ends up there: the appeal of these little switches is that you can feed one with PoE from your main switch — one cable to a remote corner, no outlet needed. Elegant. And it silently drops your budget from 202W to 42W, or to 16W if the feeding port is only PoE+.
The trap has a second half
The plain USW-Ultra has the identical spec table — the same 202W-on-adapter figure. But the AC adapter is excluded. It doesn’t come in the box.
So the switch that publishes “202W” arrives capable of 42W (PoE++ input) or 16W (PoE+ input), until you buy an adapter separately.
The same conditional applies to the USW-Flex-2.5G-8-PoE, also adapter-excluded:
| Input | Budget |
|---|---|
| 210W AC adapter | 196W |
| PoE+++ input | 76W |
| PoE++ input | 46W |
| PoE+ input | 16W |
Three rules from this:
- Never quote “210W” as a flat budget. It is a conditional maximum, available on exactly one input.
- Check whether the adapter is in the box. USW-Ultra-210W: included. USW-Ultra: excluded. USW-Flex-2.5G-8-PoE: excluded.
- If you feed a compact switch with PoE, budget 42W and be pleased if you get more.
Also note: the USW-Ultra tops out at PoE+ (30W) per port. Even on its adapter with 202W in the tank, it cannot power a 50W door hub. Not enough on any single port. Total budget and per-port ceiling are two different limits and both must pass.
By contrast: a switch that means what it says
The USW-Pro-24-PoE publishes 400W, flat, unconditional. It’s mains-powered, rack-mounted, 24 PoE ports (16 PoE+, 8 PoE++), 2× 10G SFP+ uplinks. 400W means 400W. All-in $1,025 ($950 base + $75 surcharge).
That’s the difference you’re paying for. Not just more watts — a number that doesn’t have footnotes.
How to size a switch — the actual arithmetic
Three questions: how many watts, how many ports, and what’s the biggest single port need?
Worked example: a house with cameras, Wi-Fi, and one door
The device list:
| Device | Qty | Watts each | Subtotal | Port tier |
|---|---|---|---|---|
| G6 Turret camera | 4 | 12.5W | 50.0W | PoE |
| G6 Bullet camera | 2 | 9.9W | 19.8W | PoE |
| U7 Pro access point | 2 | 21W | 42.0W | PoE+ |
| UA-Hub-Door (one door) | 1 | 50W | 50.0W | PoE++ |
| Total | 161.8W |
Step 1 — add headroom. Never buy to the exact number. Devices peak above their idle draw, cable runs lose a little to resistance, and you will add something. We use 25%:
161.8W × 1.25 = 202.3W required
Step 2 — count ports. Including the uplink.
4 + 2 + 2 + 1 = 9 PoE devices + 1 uplink to the gateway = 10 ports minimum
That uplink is the most-forgotten port in the trade. It carries every device’s traffic and it uses a physical port. Count it.
Step 3 — check the biggest single port. The door hub needs PoE++ (64W). So the switch needs PoE++ ports, not just enough total watts.
Step 4 — now check the candidates:
| Switch | Budget | Ports | Verdict |
|---|---|---|---|
| USW-Ultra-210W | 202W on its adapter — 42W on PoE input | 8 (7 PoE) | ❌ Fails three ways. 9 PoE devices won’t fit in 7 ports. PoE+ ceiling of 30W can’t run the door hub at all. And if it’s PoE-fed, 42W doesn’t even cover the cameras. |
| USW-Pro-Max-16-PoE | 180W | 18 (16 PoE) | ⚠️ Marginal. 161.8W fits inside 180W — but that’s 89% loaded with no headroom. One more camera and it’s over. Not where you want to live. |
| USW-Pro-24-PoE | 400W | 26 (24 PoE, 8 of them PoE++) | ✅ Yes. 202W required against 400W available — 49% loaded. Room for eight more cameras. PoE++ ports for the door hub. Real 10G uplinks. |
Answer: the USW-Pro-24-PoE. Not because 161.8W needs 400W — it doesn’t. Because 89% loaded is a switch you’ll replace, and 49% loaded is a switch you’ll add to. The gap in price buys the next four years.
That’s the whole method: add up the real watts, add 25%, count ports including the uplink, check the single biggest port need, then pick the switch that passes all four with room left.
Why two switches can beat one big one
Instinct says one big switch is simpler and cheaper. Often it isn’t. The general principle: put the ports near the devices.
1. Cable length is the hidden cost. Network cable has a hard 100-metre limit — but long before that, every extra metre is labour, and labour is most of what a cable run costs. A building with devices at both ends running everything back to one rack means dozens of long runs. Two small switches, each near its own cluster, means dozens of short runs and only one long cable joining the two. That single cable is often the cheapest part of the whole job.
2. Power arrives closer to where it’s spent. PoE loses a little to resistance over distance. Shorter runs, less lost — and a device fed from 15 metres away has more comfortable margin than one fed from 85.
3. Blast radius. One switch dies and everything dies. Two switches means half a building keeps working while you fix the other half. For a business, that’s the difference between a bad morning and a closed day.
4. It’s often cheaper. Two mid-sized switches frequently cost less than one 48-port monster — and buy you spare ports at both ends instead of 24 spare ports in a room where nothing needs them.
When one big switch does win: everything genuinely is in one place, or you need one high-power budget in a single pool rather than two smaller ones that can’t lend to each other.
There’s no formula. It’s a floor plan question — where the devices are, where the cable can physically go, where there’s power and a place to hang a box.
Step up / step down
The ladder view: what’s directly above any model, what’s directly below, and what actually changes when you move.
| Model | Price (all-in CAD) | Step up to → (the one reason) | Step down to → (when that’s right) |
|---|---|---|---|
| USW-Flex-Mini | $39 all-in — cart-verified, $0 surcharge | USW-Ultra — 7 PoE+ ports appear (it has zero PoE output) | Nothing. This is the floor. |
| USW-Ultra | Not in our verified price data | USW-Ultra-210W — the same switch with the 210 W adapter in the box: 202 W instead of 42 W | USW-Flex-Mini — only if nothing needs power |
| USW-Ultra-210W | $307 all-in — cart-verified | USW-Pro-24-PoE — an unconditional 400 W, 24 ports, L3, PoE++ on 8 | USW-Ultra — only if you’re buying the 210 W adapter separately anyway |
| USW-Pro-24-PoE | $1,025 all-in — cart-verified | USW-Pro-48-PoE — 48 ports and 600 W | USW-Ultra-210W — 202 W and 7 ports covers a house |
| USW-Pro-48-PoE | $1,617 ($1,499 + $118 — cart-verified) | USW-Pro-HD-24-PoE — 600 W across 24 ports instead of 48 | USW-Pro-24-PoE — do the PoE arithmetic first: 48 ports at 600 W is 12.5 W per port averaged |
| USW-Pro-HD-24-PoE | Not in our verified price data | USW-Pro-XG-24-PoE — 720 W, PoE+++, 25G SFP28 | USW-Pro-48-PoE — if port count beats watts-per-port |
| USW-Pro-XG-24-PoE | Not in our verified price data | USW-Pro-XG-48-PoE — 48 ports, PoE+++ | USW-Pro-HD-24-PoE — 600 W vs 720 W. If nothing needs PoE+++, that’s 120 W and a fibre standard you aren’t using. |
The one step that actually matters: USW-Ultra → USW-Ultra-210W. They share the same published spec table. The difference is the power adapter in the box. Without it the budget is 42 W on a PoE++ input (or 16 W on PoE+); with the 210 W adapter it’s 202 W. That is three cameras versus sixteen from an identical-looking switch — and it’s invisible unless you read Ubiquiti’s conditional-budget footnote.
Product Ladders: Step Up, Step Down — every UniFi family laddered in full, with the “don’t pay for this” note for each one. Built for anyone training staff or comparing two models on a shelf.
Related
- Choosing a Gateway — the brain the switch plugs into
- Choosing Cameras — where the wattages above come from
- Choosing Wi-Fi Access Points — the other big PoE consumer
- Glossary — PoE tiers, uplink, patch panel, home-run
Sizing a switch properly means knowing what’s going on the end of every cable — including the ones you haven’t decided on yet. AVNFi can do that count with you.