Does 4G consume more battery than 3G if I don't use it for data? Each generation of G consumes more battery  [( 4G compared to 3G or 2G) or ( 3G compared to 2G) ] than the previous one when used for data, since more complex algorithms are required to process higher data speeds

My question is if I don't use mobile data at all ( instead use Wi-Fi), but leave the mobile on 4G, will the battery consumption be the same or more as compared to 3G ( and on similar lines 3G Vs 2G), given identical usage and signal strength?

(I haven't found anything that talks of this, but I suspect power consumption would be higher)
...
  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.