This low-cost fund lets you own all of the energy stocks in the S&P 500. By Lawrence Carrel, Contributing Editor March 31, 2011 The Energy Select Sector SPDR (symbol XLE), the oldest exchange-traded fund to focus on the energy business, remains one of the best for providing you with a diversified package of stocks in the oil, coal and natural gas industries. And with nearly $12 billion in assets, it's one of the largest ETFs.Energy SPDR is one of nine Select Sector SPDR ETFs. Combined, the funds contain all 500 stocks in Standard & Poor's 500-stock index, with each ETF corresponding to one of the nine business sectors represented in the index. As a result, all of the firms in the Sector SPDR ETFs are based in the U.S. However, because most of Energy Select's companies, led by ExxonMobil, have multinational operations, the ETF offers some global exposure (its smallest holding in mid April was Helmerich & Payne, a contract driller). The only time a change is made to a portfolio is when a company is added to or dropped from the S&P 500. Energy SPDR is a favorite of professional investors because of its high liquidity. More than 15 million shares trade daily, on average, and the bid-ask spread (the difference between the highest price a buyer is willing to pay for a share of the ETF and the lowest price for which a seller is willing to sell it) is typically a penny a share. Moreover, if you want to bet against the energy sector, the ETF is easy to sell short. Individual investors love Energy SPDR for its low operating cost, just 0.2% a year.