How to make AC plugs work without shore power.

Thanks for your comments. I need to run a portable 900 watt heater. So I would need a good inverter capable of running over 900 watts continuously . I would only be able to run this heater for a few hours or I will drain the battery too much. I will not be able to use a generator at the locations where I will not have shore power.

Are there other considerations for this intended use?

Thanks.