As with all high power inverter questions don't just think of how much energy you can pull out, think also about how you are going to put it back in...
Using this handy tool heating a litre of water from 20 degrees to boiling is going to be about 10min at 600w
That's a sixth of an hour so you're going to pull about 10Ah of capacity off the battery.
That's not terrible if you just need to do it occasionally on the road or off EHU - but it's about 20 minutes of engine charging (assuming 30A) or about an hour and quarter of good solar charging (assuming 100W) to recover.
Using this handy tool heating a litre of water from 20 degrees to boiling is going to be about 10min at 600w
That's a sixth of an hour so you're going to pull about 10Ah of capacity off the battery.
That's not terrible if you just need to do it occasionally on the road or off EHU - but it's about 20 minutes of engine charging (assuming 30A) or about an hour and quarter of good solar charging (assuming 100W) to recover.