All cellular data connections are shut down when connected to Wifi. In the case of LTE, the radio is off. In the case of CDMA, radio is on, but 1xRTT voice only (no EVDO). You should notice better battery life on wifi. I think I can go all day at home on the weekend on wifi and the battery only drops 30% max. Allegedly, right? Do you blame the radio? My stock Incredible couldn't make it to lunch from 6am without needing a battery swap. Literally would be down in the teens with light usage. I switched to CM7 and my battery life tripled. Crappy HTC ROM? I haven't noticed a difference between stock and custom ROMs on the Charge, but I can go 6am to 6pm on about 70% of my battery with 4G on all day. Conditionally, if you're pushing/pulling serious data on a weak signal, LTE will suck your battery dry, moreso than EVDO. But on good signal strength, I see absolutely no difference between 3G and 4G with light data usage (ie. not downloading large apps or videos at a time, but rather web browsing and such). Battery life is dynamic to begin with, hinging on a number of factors. It's a bit shortsighted to pin the problems on 4G exclusively.