If your security cameras keep dropping offline for no obvious reason, the cause is often the PoE switch running out of power rather than a faulty camera. Every PoE switch has a total power budget shared across all its ports, and once the cameras draw more watts than that budget allows, the switch quietly starts shutting ports down.
What a PoE power budget actually is
Power over Ethernet means a single network cable carries both data and power out to the camera, so there is no separate power supply at the camera end. The switch supplies that power, and it can only supply so much. That ceiling is the power budget: the total wattage the switch can deliver across every port at once — typically 120 W, 150 W or 250 W depending on the model.
Port count and power budget are two different limits, and this is where most people get caught. An eight-port PoE switch does not promise eight cameras. It promises eight sockets and a fixed number of watts to share between them.
How to add up what your cameras draw
Find the power draw of each camera on its spec sheet, add them together, and compare the total against the switch’s budget. As a rough guide, a standard fixed bullet or dome camera pulls around 8 to 10 W, so eight of them is an 80 W load — comfortable on a 150 W switch. Keep that headroom deliberately: long cable runs lose a little power along the way, so a camera at the end of a 90 metre run draws slightly more than one sitting three metres away.
The PTZ trap
Here is the one that breaks systems. A pan-tilt-zoom dome has motors to drive, a zoom lens to move and far stronger infrared illuminators, so it commonly pulls 30 W or more — the budget of roughly four regular cameras.
So a switch that ran eight fixed cameras happily for two years can fail the moment someone swaps two of them for PTZs at the driveway and the loading dock. Nothing was added and the port count did not change, but the load went from 80 W to about 124 W.
Why it looks like a broken camera
Go over the budget and the switch does not warn you. It simply cuts power to ports, usually the highest-numbered or lowest-priority ones first. Cameras disappear from the recorder and recording on those channels stops. Often they come back during the day when the infrared switches off and the load drops, then vanish again after dark when every illuminator fires up at once.
That intermittent, after-dark pattern is exactly what a failing camera looks like, which is why systems get misdiagnosed. The cameras are fine, the recorder is fine, the cable is fine — the switch has run out of power to give. If you can log into the switch, the per-port draw and total consumption figures confirm it in seconds.
What we recommend for Kitchener-Waterloo homes and businesses
Size the switch for the cameras you might add later, not just the ones going in today. On local installs we leave 30 to 40 per cent of the budget free and assume at least one PTZ will eventually appear — driveways in Waterloo Region are long, and a plate-capture PTZ at the road is a very common second-phase addition.
Winter matters here too. Heaters and de-icers on exterior housings only draw power when it is cold, so a system specced in July can sit at its limit through a Kitchener January. Add their draw and assume they will all be on at once during a cold snap.
Farm and warehouse yards around Cambridge and Guelph are the other common case: long runs to gates and outbuildings mean real voltage drop, and yard coverage usually means PTZs. There we would rather fit a switch well above the day-one load, or split the cameras across two, than return in a year to replace one that has been outgrown.
FAQ
How many cameras can an 8-port PoE switch run?
It depends on the power budget and the cameras, not the port count. A 120 W switch runs eight 10 W fixed cameras comfortably. Put three PTZs on it and you are near the limit with five ports still empty. Check the watts, not the sockets.
What happens if I exceed the PoE power budget?
The switch starts shutting down ports to protect itself. Affected cameras go offline and stop recording, often intermittently, and nothing tells you why. It is not usually damaging to the hardware, but the gap in your footage is real and permanent.
Can I just add a second switch instead of replacing it?
Often yes, and it is frequently the cheaper fix. Each switch brings its own budget, so splitting the cameras spreads the load. Make sure the link between the switches and back to the recorder uses a gigabit uplink port, or you move the bottleneck from power to bandwidth.
If your cameras keep dropping offline and you are not sure the switch is the cause, we will check it. SpyonSecurity offers a free site survey across Kitchener, Waterloo, Cambridge and Guelph — we measure what your cameras actually draw, tell you how much headroom is left, and say plainly whether the switch needs replacing. Call 226-227-7966 or get in touch here.