How to compute dissipation of switching regulator considering the input?
At 36V input, 5V 0.5A output, efficiency is rated at ~80%.

So to output 2.5W of power (0.5A*5V), you draw 3.125W (2.5W/0.8). Losses are 0.625W.




  Will I able to use it on 36V input to have a really 5V, 1A output?


Yes, the output at 1.5A with 36Vin is represented below: