Wi-Fi, ZigBee and Z-Wave are types of wireless communication for a lot of current smart home devices. There are other types of wireless communication but that's not what I am discussing today.
If you have wireless internet access at home chances are you have heard of Wi-Fi or wifi or WiFi or Wi-fi. Wi-Fi has been around for a while and is continually being improved upon. Based on IEEE 802.11 standards. Wi-Fi compatible devices can connect to the internet via WLAN (wireless local area network) and a wireless access point or AP. Most people with wireless internet will have a basic Wi-Fi router supplied by their internet service provider (ISP). This router is also a wireless access point (AP). The access point or AP communicates with all of your Wi-Fi devices such as your phone, laptop, TV etc. Each device connects to your AP individually via a wireless signal or radio frequency. This is called a star topography as the AP is in the middle with all the devices around the outside connected individually with their own line of communication each taking their turn to talk to the AP. All communication is via the AP so if one device wants to talk to another device it has to talk through the AP. There can be coverage issues with devices further away having a harder time sending and receiving information. Most older devices and some newer work on the 2.4GHz channel. This is a range of frequencies around 2.4GHz. You can imagine over time with more and more devices using this frequency it can become quite crowded making it harder for devices to have their turn getting information to and from the AP. The introduction of the 5GHz band has helped with congestion but it has its own limitations although the newer Wi-Fi 6 is helping to address some of those. Generally speaking, Wi-Fi has been very successful and reliable at communicating data which has made it popular for Iot devices and smart home products and it is relatively easy to use. See our Wi-Fi Smart Switch for an example. There are limitations on how many devices a single AP can handle, a maximum of 250 devices is a number that is often quoted but most home users would struggle to reach these limits even if they are accurate and generally speaking smart home devices tend to use very little bandwidth. Range is another issue but can be address with stronger signals or with multiple AP’s or a combination of both.
ZigBee is another type of wireless communication and uses IEEE 802.15.4 also on the 2.4GHz band. Similar to Wi-Fi in many ways but it uses a mesh topography. There is a hub that works in a similar way to a router/AP but alongside it. Unlike Wi-Fi, ZigBee devices can communicate with each other as well as the hub. This can be beneficial for devices that are further away because information can be passed through closer devices or routed through multiple devices. Having a hub communicating with the smart home devices also takes load off the router/AP as devices can talk to each other without having to involve the router. This has the added benefit of reducing power requirements as the transmit distances can be shorter. ZigBee does use the same 2.4GHz band so there can still be crowding issues and the hub to router/AP adds another layer of communication. ZigBee is said to be able to connect 1000’s of devices to a single network so you would find it hard to connect too many devices.
Z-Wave is also a mesh topography where devices can communicate with each other directly as well as a hub. Z-Wave works over low-energy radio waves on a dedicated frequency. This frequency is different country to country but ranges around 800-900MHz. The benefit of this lower frequency is there is very little congestion and it has a good transmit range. Z-Wave is said to be able to connect up to 232 devices. The Z-Wave country to country frequency differences mean devices made for one country in most case will not work in another country and as some frequencies are reserved it can actually be illegal to use devices from another country.
This has been a very simplified run down on my understanding of the different technologies, there is a huge amount of detail I have skimmed over and tried to make simpler. Each technology has pros and cons. I haven’t touched on security or price but put in very very basic terms anecdotally per device Wi-Fi is probably the least secure but also the cheapest, Z-Wave is most likely the most secure but also more expensive and ZigBee is somewhere in the middle. It’s nice to have everything under one roof and have it all work nicely together but diversification can help reduce risk. For me I have a mix of all 3 types and manage to make it all work for what I want. Have a think about your priorities and choose devices based on that. If you have made it reading this far well done you deserve a chocolate fish (sorry I don't have any). Feel free to get in touch if you have any questions or comments. Cheers Luke.