I came across this old thread and thought I would add some more fuel to the fire.
Aside from guesswork, opinions and speculation, here are some technical facts about Z-Wave and Zigbee:
- Frequency Band
Z-Wave - 908 MHz (US), 860 MHz (Europe)
Zigbee - 2.4 GHz (world-wade)
As a rule of thumb, the lower the frequency, the longer the range and better obstacle penetration. 2.4 GHz band is particularly bad for two reasons: (a) this is the frequency where all your WiFi, Bluetooth, wireless keyboards and most other consumer electronics gadgets transmit, so it’s indeed a crowded place. And (b), it’s a frequency used by microwave ovens. For example, one particularly nasty microwave in my kitchen practically kills all WiFi in my house. I give a score to Z-Wave on this one.
- RF Modulation
Z-Wave - FSK/GFSK (Gaussian Frequency Shift Keying)
Zigbee - O-QPSK (Offset Quadrature Phase Shift Keying)
Long story short, Z-Wave uses simple “run-of-the-mill” FSK modulation, while Zigbee sports more advanced modulation technique called spread spectrum, which makes Zigbee more noise-immune. This definitely helps it co-exist with all other radios in the 2.4 GHz band (see #1). Also, Zigbee network coordinator can choose one of 16 available channels, while Z-Wave is confined to a single frequency. Zigbee is definitely ahead on this one.
Z-Wave - 9.6 / 40 / 100 kbps (depending on version)
Zigbee - 250 kbps
This how fast data is being transmitted. So Zigbee is more than twice as fast as the fastest Z-Wave version. But home automation devices typically transmit tiny amounts of information, just a few bytes when a door contact opens or motion is detected. So does it matter if it takes 0.02 or 0.01 seconds to transmit a message? Yes, for battery-powered devices it does! Faster speed means that the radio has to be powered for shorter period of time to transmit the same message, leading (theoretically) to longer battery life. Zigbee has an advantage on this one too.
- Network Topology
Z-Wave - Mesh network with multiple controllers
Zigbee - Mesh network with single controller
Both Z-Wave and Zigbee are mesh networks, meaning that any mains-powered node can act as a re-transmitter, thus increasing network coverage. Z-Wave however has an advantage, allowing multiple controllers. I.e. a secondary controller (e.g. a remote control or a key fob) can talk directly to light switches or sockets. In Zigbee on the other hand, all communications must go through single coordinator. Z-Wave network will continue to function if the main controller goes down, but Zigbee will not. One more score for Z-Wave.
Z-Wave - Good
Zigbee - Bad
Z-Wave is a proprietary protocol designed by a single company for a single purpose (home automation). It is therefore more focused and more to the point. Zigbee, on the other hand, was designed by a committee with two dozen players pulling in two dozen different directions. There are multiple domains within Zigbee specification, called “profiles” which are in fact different and sometimes incompatible “standards” in its own right. What’s even worse, there are multiple, competing profiles that essentially do the same thing. There is for example, the Home Automation Profile, the Building Automation Profile and the Light Link Profile, all of which do essentially the same thing - turn the lights on and off. That’s why it’s hard to find Zigbee devices from different vendors that can talk to each other. Z-Wave definitely wins this one.
Z-Wave - High
Zigbee - Low
Z-Wave has been accepted as technology of choice by several major manufacturers, including GE. I read somewhere recently that up to 80% of all home automation products in US use Z-Wave. Don’t know if its true, but it’s definitely easier to find a Z-Wave switch or socket
than Zigbee one. One more score for Z-Wave on this one.
Zigbee radios tend to be more complex and hence more expensive, leading to higher end-product price, although production volume probably has bigger impact on the final price tag. Z-Wave is slightly ahead on this one, but I’ll call it a tie.
- Total Score
Z-Wave - 5
Zigbee - 3
So, it looks like Z-Wave comes ahead in this simple contest. Personally, I think that although Zigbee is technically superior, all its advantages are less important then almost universal adoptance and commercial success enjoyed by Z-Wave. After all, in my experience Z-Wave works very reliably. What do you think?