The battery consumption should go up, but as telepathy-haze is optimized (more than telepathy-butterfly as it seems) it should be ok.

If your phone lasts from 7am to 22pm normally, I think you'd have to expect a drop by 2-4 (?) hours on wireless. 3G / 3.5G will be more expensive. At least that's my impression from my previous usage.

But battery consumption is hard to calculate...so everything is approximate.

Note that every protocol behaves different. Some may have "push notifications" others will regulary poll...if one of your contacts just switches all the day from offline to online it will also consume more...

Test it for two to three days and report back. It was ok for me.