“TAN is not only one of the worst ETFs to own in the month of July, according to data from Schaeffer’s Senior Quantitative Analyst Rocky White — it also generates the worst returns in the third quarter and the second half of the year, going back 10 years. Specifically, TAN averages a monthly loss of 1.35% in July, ending higher just 44% of the time. In the third quarter, TAN has lost 6.18%, on average, with a win rate of just 33%. In the second half of the year, the Guggenheim Solar ETF has dropped a whopping 15.95%, on average, with a win rate of 33% — the worst of all ETFs on our list,” according to Schaeffer’s.

Related: The Boost for Solar ETFs Could Keep Shining

Solar stocks slid last year as increased competition pushed prices lower while customers pushed off on purchases in hopes of further cheaper prices, especially with Chinese companies raising production. Still, there are some positive signs.

Government subsidies helped green energy technology get its foot in the door, but lower costs will help the industry compete with fossil fuel. Economies of scale has been the top driver of falling prices – for example, the cost of solar power has plunged to 1/150th of its level since the 1970s and solar installation has surged 115,000-fold.

For more information on the photovoltaic panel industry, visit our solar category.