PoE vs PoE+ for wall tablets: which switch port you need

Spec a wall-mounted Android tablet and the PoE vs PoE+ question stops being marketing fluff. It's the gap between a display that boots and one that browns out under load. We build commercial Android tablets for integrators. And this shows up on almost every quote: do I need a PoE port or a PoE+ port? Start with the IEEE standards. Then look at the tablet's DC input rating, the switch budget, and the cable in the wall.

PoE, PoE+, and PoE++: The Three Standards at a Glance

Power over Ethernet comes in three generations. The original IEEE 802.3af PoE standard showed up in 2003, maxing out at 15.4 watts at the power sourcing equipment (PSE) TechTarget. Run 100 meters of cable, though, and the powered device (PD) only sees about 12.95 watts. Cable losses eat the rest TechTarget. Then came PoE+, IEEE 802.3at, ratified in 2009. It pushed PSE power to 30W Cisco, and the PD gets roughly 25.5 watts guaranteed TechTarget. The newest standard? IEEE 802.3bt, often called PoE++. It adds Type 3, which supports up to 51 W delivered to a PD, and Type 4, up to 71.3 W delivered to a PD Ethernet Alliance. Type 3 and Type 4 use all four wire pairs. PoE and PoE+ stick to two. In the field, you'll see PoE on basic IP phones and simple sensors, PoE+ on most small displays and access points, and PoE++ on laptops, large displays, and PTZ cameras.

Reading a Tablet’s DC Input to Choose the Right PoE Port

A tablet's DC input rating tells you its worst-case power draw. The label might read 12 V / 1.5 A. Multiply volts by amps to get watts: 12 × 1.5 = 18 W. That’s the max the tablet expects from its AC adapter. For PoE, though, you look at guaranteed power at the device-not the PSE maximum. A PoE port guarantees only 12.95 W. So an 18 W tablet won’t run reliably. PoE+ guarantees 25.5 W. That covers 18 W with room for cable loss and startup spikes.

Say a buyer is checking a 10.1-inch wall tablet rated 12 V / 1.5 A. That’s 18 W. So it needs PoE+. PoE would be too tight. Now picture a 17.3-inch tablet rated 12 V / 3 A. That’s 36 W-above the PoE+ guarantee. An adapter rating is a ceiling, not the running draw, so ask for the rated draw of the PoE option or plan a DC supply. We make both sizes. The HP1012T 10.1-inch tablet lists IEEE802.3at/af PoE support. The HP1733T 17.3-inch tablet has an IEEE802.3at/af option. Spec tables show which models include PoE and which offer it as an option.

PoE Classes and Power Negotiation

PoE isn't just a fixed voltage. PSE and PD negotiate power using classes. Classes 0-4 cover PoE and PoE+. Class 0 is default, up to 15.4 W at the PSE. Class 1 is 4 W, Class 2 is 7 W, Class 3 is 15.4 W, Class 4 is 30 W. PoE++ adds Classes 5-8: Class 5 is 45 W at the PSE, Class 6 is 60 W, Class 7 is 75 W, Class 8 is 90 W Cisco. Assigned Class 5 or higher? Power needs 4 pairs Ethernet Alliance. The handshake is active. PSE sends a detection voltage, PD responds with a classification signature, and PSE allocates the class. Passive PoE skips all that. It just puts voltage on the wire, which can damage devices. So always use active PoE for commercial tablets.

Switch Power Budget and Midspan Injectors

Per-port power ratings don't tell the whole story. Check the total power budget too. Say you've got 8 PoE+ ports, each capable of 25.5 W. The switch might only have a 124 W power supply. So you can't run all 8 at full load at once. Add up the wattage of every connected device. Then tack on headroom for startup surges and future expansion. For 8 devices at 25.5 W each, that's 204 W minimum, plus headroom. Look for a switch with a bigger power supply.

No PoE on your switch? A midspan injector adds power to the cable between the switch and the device. It's a small box with a data in port, a data+power out port, and its own AC adapter. Injectors come in single-port and multi-port versions. They follow the same 802.3af/at/bt standards. They're handy for one-off installs or when you don't want to replace a working switch. Just remember, the injector's power rating must match the device's class.

Cable Category and Run Length Limits

PoE runs over standard Ethernet cable, but category matters. Cat5e is the minimum for PoE and PoE+. For PoE++ Type 3 and Type 4, you'll want Cat6A. Max channel length? 100 meters. That's a hard limit from the standard, not a suggestion. Go beyond it and you'll hit voltage drop and signal degradation. Use solid copper cable, not copper-clad aluminum (CCA). CCA has higher resistance and can overheat under PoE loads. Higher wattage means more current, which means more heat in the cable bundle. Running many PoE++ lines together? Think about ventilation or larger gauge cable.

Hopestar PoE Tablets: What the Spec Tables Say

IEEE802.3at/af. That's what our commercial Android tablets list for PoE. Both PoE and PoE+ switches work. Actual power draw? Depends on the model and configuration. Some models have PoE standard, others optional. Take the HP1012T 10.1-inch tablet. It lists IEEE802.3at/af. The HP1733T 17.3-inch tablet shows it as an option. The PoE tablet product list covers all models with PoE support. Need a meeting room display? Check the meeting room tablet page. For larger screens, the 17-inch tablet page has options. Power draw depends on the configuration, so ask us for the DC input rating of the model you're considering. That's the number you use to size the PoE port.

Decision Checklist: PoE vs PoE+ for Your Display Deployment

Here's a checklist for the next project:

• List every device's DC input rating. Volts and amps.
• Multiply volts by amps. That's your wattage. Do it for each one.
• Now check the number: ≤ 12.95 W means PoE, ≤ 25.5 W means PoE+, and ≤ 51 W means PoE++ Type 3.
• Check per-port power on the switch. And the total power budget.
• Confirm cable category and run length. Cat5e for PoE/PoE+, Cat6A for PoE++. Max is 100 m.
• Not sure? Pick the higher standard. PoE+ ports work fine with PoE devices.

Still stuck? Send us your device list. We'll sort it out. For a quote, include models and quantities. Tell us if you need PoE as standard or optional. You can reach us through the contact page.