Plenty of discourse has been swirling around Berkshire Hathaway's recent investment in energy giant ExxonMobil (NYSE:XOM). For the second quarter in a row, Warren Buffett added a Big Oil name to his portfolio, but both ExxonMobil and Suncor (NYSE:SU) are just pieces to his energy empire. In this segment, we rank the top four energy companies in Berkshire's immense portfolio.  

This segment is from Tuesday's edition of "Digging for Value," in which sector analysts Joel South and Taylor Muckerman discuss energy and materials news with host Alison Southwick. The twice-weekly show can be viewed on Tuesdays and Thursdays. It can also be found on Twitter, along with our extended coverage of the energy and materials sectors @TMFEnergy.