Difference between 5G vs 4G in terms of energy consumption
Since you require low data rates and a lower power consumption, why not look into LPWAN(Low Power Wide Area Network) Technology. 

3G-PP has proposed 2 LPWAN technologies, LTE-M and NB-IoT which can be used to reduce power consumption and increase range at lower data rates. LTE-M works on existing LTE towers and hence you can be using it wherever there is an LTE coverage.

There are many options such as LoRa, Sigfox, RPMA, etc that you could look into for such applications