WiFi devices connect directly to your WiFi network and communicate with your Home Hub directly over your local network.
Not every device supports WiFi, and mostly those that are battery powered do not as they just don't have enough power to support it. Good candidates for WiFi are items that are always plugged in, or that are wired directly in to your homes electricity, such as light switches, smart bulbs, large appliances, fans, and TVs. Many (potentially, most) of the devices in your smart home will be wireless, battery operated sensors, cameras, or lights.
These devices have full and complete access to the internet (unless you firewall them off), and are almost always 2.4ghz exclusive which can make setup a bit of a pain unless you have a dedicated 2.4ghz network. Often, you will need to set your access point to be exclusively 2.4ghz to ensure your phone or tablet and the device are all on 2.4ghz, to allow setup to finish — often this is trivial to do, however it can require restarting your WiFi to make the change and then a second time to undo it when you're done.
A solution to this is setting up a second dedicated 2.4ghz network.
Dedicated Smart Home Network
There are several reasons to setup a dedicated smart home network, privacy, security, and performance being the primary reasons.
Setting up a dedicated 2.4ghz network can be quite difficult and comes with several issues.
Many modern WiFi access points allow you to create a secondary "guest" network. Assuming it allows you to limit it to the 2.4ghz frequency band only, these are frequently setup such that devices cannot talk to each other to create a secure network experience for visitors to your home, making them unsuitable for your smart home network.
If the reason you want to have a separate network is to limit access to your private data (e.g. the contents of your laptop) by limiting the number of devices on your primary network that could be compromised, it's common to block the dedicated smart home network from being able to access (or be accessed from) the internet, however, some devices — such as your TV streaming box — need access to the internet.
Assuming you do setup an isolated secondary network, with everything that doesn't require internet blocked off… you still need to communicate with the devices from a controller like your phone or tablet. You can either put it on the same network, exposing it to a bunch of devices you were trying to isolate from your private devices, or you need to connect via the public internet introducing a lot of latency and potentially noticeable performance slow downs.
Coverage
The other main concern with WiFi is signal coverage. Traditional access points (like those provided by your ISP, or non-mesh consumer home WiFi solutions) project their single from a single source — meaning the further away from the source the worse your signal is likely to be. You may not notice this as much in the places you commonly work and play, as you've already resolved those issues, but other parts of you home may not be so lucky.
The thing about a smart home is that it needs to encompass your entire home. There are areas of your home that never needed WiFi that suddenly do. Whether that's an a smart light in your outdoor shed, sprinkler systems and garage door openers in your garage (which may or may not be attached to your home!), or just the closet under the stairs. Most dedicated protocols for smart homes use a mesh system whereby each device in the network can relay the signal — so long as there is a chain of nearby devices between your furthest device and the hub, your device can stay connected.
The Good
- Easy Setup
- Just like any other networked device in your home
The Bad
- Most devices use 2.4ghz WiFi band which means you can’t go exclusively 5ghz
- Interference can be an issue, particularly given it’s 2.4ghz
- Uses a lot of power, so it’s mostly used for devices that are mains powered
Final Thoughts
For the right devices, WiFi is reasonably robust, fast, and easy. However, the majority of devices just don't have the power to support it. Add to that the fact that smart home devices end up In areas far less likely to have good coverage and a protocol that supports mesh networking often allows a far more robust and performant solution that has far lower power requirements.