This router is a gem of a network device. It has a lot of the advance networking feature including PoE for a meager price of $60. It's so popular that it is often out of stock on the manufacturer's website:
https://store.ui.com/collections/operator-isp-infrastructure/products/edgerouter-x
https://www.ui.com/download/edgemax/edgerouter-x/er-x
If you want more ports on the router, the next best thing is the EdgeRouter 10X
https://store.ui.com/collections/operator-edgemax-routers/products/edgerouter-10x
https://www.ui.com/download/edgemax/edgerouter-10x/er-10x
Here is the entire family of the EdgeRouters:
https://store.ui.com/collections/operator-edgemax-routers
Used in conjunction with a UniFi6 Lite access point, you will have a basic rock solid wifi system that almost rivals one found in big business. If you want even more features from the access point, have the UniFi6 Lite be managed by a controller by replacing the EdgeRouter with a Dream Router
https://store.ui.com/collections/unifi-network-wireless/products/u6-lite-us
https://www.ui.com/download/unifi/unifi-6-lite-ap/u6-lite
https://store.ui.com/collections/unifi-network-unifi-os-consoles/products/dream-router
This post focuses on the Power over Ethernet aspect of the EdgeRouter.
The EdgeRouter X comes with a two-prong AC power brick that can output 12V at 0.5A. While this can power the router, there is not enough juice to let you use the eth4 as the source to power a PoE device such as the access point. However, if you use a 24V 0.5A power source -- either a PoE injector on eth0 or a power adapter via the DC barrel jack -- you can enable PoE output on eth4. Be aware that this is 24V passive PoE. As such, it will only work with end devices designed for this particular type of PoE. If passive PoE is enabled and a non-PoE device is connected, this power can potentially damage these devices since this is passive PoE. Unlike 802.3af/at/bt, it does not have an active process to auto-detect/negotiate power delivery before power is sent. This eth4 cannot be made to be 802.3af/at. For that you have to get a different PoE device that has support this technology. Interestingly, the UniFi6 Lite access point can take both 24V passive PoE and 802.3af/at PoE.
You can get this 24V power adapter here:
https://www.amazon.com/gp/product/B0194B7ZS0
However, unless you have absolute control over the physical layout of the network, it's best to not use passive PoE at all in favor of 802.3af/at/bt for safety.
https://community.ui.com/questions/I-bought-the-EdgeRouter-X-can-the-power-supply-deliver-24v-PoE-or-need-different-adapter/f7692781-a984-4659-8d1c-e89af19bc8fc
