The week ahead also features several important economic releases including March retail sales, beige book and the consumer price index. Here are the key ETFs to watch for the week of Monday, April 13: Guggenheim Solar ETF (NYSE: TAN ) Solar stocks have been among the top performers in 2015 amid a sharp rise that continues to show no signs of abatement. TAN tracks 29 global solar companies engaged in manufacturing and installation of clean energy equipment.