Home Automation

WiFi devices use the Internet Protocol and can communicate with online services and apps over normal computer networks.

Zigbee, Zwave, etc use a completely different protocol that can't interact with the Internet directly. These protocols are optimized for low power use and for interacting with other home automation devices over their own short range wireless channels.

These devices can technically communicate with each other directly, without a hub, but then you must use a remote control device. For example, there are ways to pair certain Zigbee switches to directly control a Zigbee lightbulb.

The hub is used to bridge the HA wireless protocol with the Internet Protocol. This way your phone (which doesn't have a Zigbee/Zwave radio) can connect to the hub and control everything.

Wifi is fine for some things, but it's power hungry, it requires an IP address for each device, and is subject to interference from other wifi devices. If you want to block all of the devices from accessing the internet, it adds some extra complexity. If you have a battery powered wifi device, it will power itself off until activated, then have to connect to your wireless network (DHCP, etc) before it can transmit, which takes a second or three.

ZigBee, ZWave, and BLE are low power protocols, and are fairly statically configured. They use less power and can have much better battery life on much smaller batteries. When activated, they connect back to their respective networks immediately, so things like smart buttons and motion sensors are very fast.

In addition to the other comments here, if you are planning on adding lots of smart devices to your home consider zigbee.

Wifi = great! But most cheap home routers start crapping out when lots of devices connect. Generally if you are going to use lots of wifi devices get a decent mesh wireless system like Unifi (**other good wifi mesh systems are on the market, this is just my experience) and you'll be good. So Wifi ok to start out, but expect problems as you grow if you are using your ISP provided router.

Wifi also means the manufacturer of your device can get it to "phone home" which has various security and privacy implications.

Wifi also means you are typically dependant on someone elses cloud and as we have seen with Chamberlain MyQ, they can degrade your device to force you to subscribe to services. Manufacturers can also go out of business and again you are sort of screwed.

Because Zigbee (Matter, but I'd personally leave that one alone for a while), Z-Wave use a hub, even if the manufacturer goes out of business there are still methods to control these devices.

Because Zigbee, Zwave, BLE, and various proprietary RF data transmission schemes aren’t WiFi.

Zigbee doesn’t use Wi-Fi.

Generally you will want to use a hub for your home automation. Most will use z-wave, zigbee and Wi-Fi. Some will also do Matter.

Using a smart home hub, you can have automation routines that tie all devices on various protocols together. The popular smart home hubs are Hubitat and Home Assistant.

No mater what you decide, home automation is not cheap. And, remember, you get what you pay for. Remember that. Lot of Wi-Fi devices require internet, and they communicate a lot with their manufacturers’ servers.

there are hubs/bridges and then there are controllers.

Every smart device requires a controller because the truth is, none of them are smart. At most you get a timer, which, let's be honest, was available back in the 60s. It's the controller that does IF/THEN logic, tying multiple devices together

Hubs/Bridges let two different technologies talk to each other. Your router is a wifi hub/ethernet bridge you already bought. So you don't need any bridges to connect Kasa devices. At least as long as your router can handle the number of devices. Many consumer routers are only given enough CPU/RAM to handle maybe two dozen devices.

So the question you need to ask yourself about Kasa is where is the controller? Who owns that? Who can turn it off? What happens if they do? For most Wifi devices the answer is "in the cloud, owned by the manufacturer, who can turn it off whenever they want and there's a good chance your switches become dumb switches".

Zigbee/ZWave needs a bridge, which is often a USB stick on a PC that acts as a controller or is integrated into a dedicated controller. Every $40 zwave radio is good for 232 devices. Zigbee devices vary but the vast majority are good for 100+ and even the most under-specced Hue hub is good for 50 zigbee bulbs.

I use HomeSeer running on a mini PC with a zwave usb radio to control my 80+ devices. if Homeseer goes under, I lose remote control until I set up a VPN server. But all my devices will still follow all their programming, I can add new devices, new rules, and let it continue to run for years if I choose.

Wifi only devices suck, so if it’s not thread you generally want zigbee which is going to need a hub.

Then some companies take that further and require their own proprietary hubs.

All devices require a hub, they need a hardware and software controller to work. It's just that many "hubs" are a wifi router and cloud services. The hubs you are referring to are just local hardware and software controllers that live in the same space.

A note about ZigBee, Bluetooth (LE or otherwise) and WiFi. They all use the same 2.4ghz frequency band. They do not communicate with each other, but they CAN and often DO interfere with each other. The neighborhood I moved into a year ago is nothing but single family homes, but I can still see anywhere between 6 and 10 WiFi networks in addition to my own. That’s not including anything else my neighbors might be using that uses 2.4ghz. Think wireless headsets, baby monitors, and the like.

I struggled with my ZigBee mesh working for a while, and then randomly some battery devices would just stop communicating. This was the worst with ZigBee wireless buttons. They may work again, if you press them 5 or 10 times. Even some wired ZigBee devices were struggling with delayed signals.

Give serious consideration to Zwave if you browse for WiFi networks in your home and see more than one or two neighbor’s networks, or if you can see your neighbor’s Bluetooth devices when you try pairing something to your phone. Zwave uses the 900mhz band, which sees MUCH less use these days, especially since 900mhz cordless landline phones are pretty uncommon now.