Actually, in most cases 4G (LTE) data should use less energy per bit to transfer your data than 3G. This may not be true for some of the early radios released since they are not as mature as 3G chipsets yet. It'll also take some time until the networks start using all power saving features available. But when devices and networks mature a little 4G should in general be more efficient.

However, since you get faster speeds you tend to use more data, which of course will use up your battery faster as well. But if you'll use it the same way you do today you'll just get faster access and should see about the same battery life, so there's nothing to be afraid of.