The State Street Energy Select Sector SPDR ETF (NYSEMKT:XLE) offers low-cost, mature energy exposure with lower volatility, whereas the Invesco Solar ETF (NYSEMKT:TAN) provides high-conviction, volatile access to the solar industry. While both funds represent the energy sector, they focus on very different sub-industries. XLE is significantly more affordable for investors, sporting an expense ratio of 0.08% compared to the 0.7% charged by the Invesco fund. The Invesco Solar ETF maintains a portfolio of 36 holdings, focusing exclusively on the solar industry with exposure to sectors such as technology at 62%, utilities at 29%, and industrials at 6%. The State Street fund, XLE, holds the biggest names in the U.S. oil and natural gas industry, providing exposure to producers and retailers like ExxonMobil and Chevron.