it's like it's using more power to sniff for 4g signal.
That's EXACTLY what is happening here. If you live somewhere where the 4G signal is nice and strong, and stretches out over your entire daily traveling area, the battery should be fine. For example, I live VERY close to Washington, DC, and I work in DC. I can always pick up a strong 4G signal, so my battery life is relatively good with 4G.