Does 4G consume more battery than 3G if I don't use it for data?
...
  The LTE radio states drain slightly more power than their counterparts
  in 3G, because the tail states (Short DRX and Long DRX) stay at the
  higher base power, while much of the 3G tail is in the FACH state
  which uses half power.
  ...


So basically 4G modules consume more energy compared with 3G modules BUT


  ...
  the IC/chip technology is improving, batteries are becoming better, 4G
  coverage is improving, technology is maturing, networks are getting
  optimized, etc. All this will lead to your 4G devices performing much
  better than 3G soon. The difference will not be noticeable anymore.
  ...


So actually you can't feel any difference between 3G-4G energy usage.

Source: here.