I am considering a magical system where a mage can manipulate temperature of objects he/she touches. Either transferring heat from other objects or directly affecting target. The trick is that they must use type of magical "fuel" which is difficult to replenish. And the more they break ordinary laws of physics, the more "fuel" is necessary. So no, they cant freeze a lake or some other large feat like that. They are also limited to what they actually touch, so they can't take energy from entire atmosphere or planet they stand on, or heat up entire blood in a human. Also, mages are rare in population so industrial scale use (to power machines) is out of question.
My main question is: Can such magic create wind or flow of water? And if so, how costly it would be assuming mage do not have energy sink (either hot or cold)
And secondary is what most destructive use it may have beside mundane lighting fires, burning/freezing touch, igniting gunpowder weapons without trigger (so they would be harder to reverse engineer) etc. I am trying to create limited system so I would like to prevent the most devastating uses.