About 12 years ago, I made my first train trip in eons and stopped at Union Station in Denver….  They had an infrared ‘cooker’ and cellophane wrapped sandwiches in a refrigerated vending machine….  They were amazing, and took me back in time quite a bit….  I looked forward to the ‘snack bar’ on every trip through Denver….  A couple of years later, they had remodeled, and, you guessed it – – the infrared machine was replaced by a microwave!!!!!  Bah……. 
 
Both machines took about the same amount of time – – not sure about energy, but the infrared machine offered a truly superior product…