It has back up power which should be able to sustain flight for about an hour as long as I don't need to use shields, repulsor fire. Less if I put all the power to the thrusters.

When I built the first reactor for my chest, it would have easily powered a house for a whole year or more. It's had substantial upgrades since then. And when you consider that all it's doing when I'm not in the suit is powering an electro-magnet. It's not like powering the suit is going to cause any major drain.