I thought I would share an email from Aeotec by Aeon Labs inquiring what are the differences between the models.
Here is the response:
The main difference between G2 and Gen5 is the change to Z-Wave Plus, overall the hardware asides from the Z-Wave update in its chipset is different: http://aeotec.com/z-wave-500-series-module-chip
Series 300 is used in G2 and G1 (DSB28 and DSB09 respectively)
Series 500 is used in Gen5
You can only take full advantage of Z-Wave Plus only if you have a Z-Wave Plus controller.
Both G1 and G2 HEM units are no longer covered under warranty.
Difference summary over all HEM devices.
HEM G1 (DSB09)
Can be battery powered or USB powered
Firmware updatable via USB port
5% error in accuracy
Can report KWH, WATT
HEM G2 (DSB28)
Must be wired into circuit breaker (EU/AU) or plugged into a socket (US
Not firmware updateable
1% error in accuracy
Automatically detects voltage and current for higher accuracy reading
Can report KWH, Watt, Voltage, Current
Can read negative and positive readings (generating and consuming power)
HEM Gen5 (ZW095)
Same as the HEM G2, but upgraded to Z-Wave Plus technology
Some added configurations settings
Can also read kvar and kvah only if the gateway supports this, so far no gateway has supported these readings.