NEW YORK ( TheStreet) -- Alternative energy ETFs have had a dismal performance over the past few months, with only one fund in positive territory this year, PowerShares WilderHill Progressive Energy Fund ( PUW).Across the board, alternative energy ETFs have suffered considerably. Funds that centralize around one specific form of energy, such as the Claymore/MAC Global Solar Index Fund ( TAN) and the Market Vectors Solar Energy fund ( KWT) within the solar power sector, or PowerShares Global Wind Energy Portfolio ( PWND) and First Trust Global Wind Energy ( FAN) within the wind power sector, have been particularly vulnerable, suffering year to date losses in the range of 27% to 31%. Broader alt-energy funds have performed slightly better, although still incurring losses between 6% and 22%. Only one fund, the PowerShares WilderHill Progressive Energy Fund has performed positively throughout the course of the year, attaining YTD growth of 1.53%. The main reason for the difference is that PUW is heavily invested in non-alternative energy companies. Instead of owning the firms developing new forms of energy and their suppliers, PUW owns companies working on bridge technologies and efficiency. This means that PUW ends up owning industrial firms involved in alternative energy as one part of their business. For instance, PUW's top holdings include Owens Corning ( OC) (3.22%), GrafTech International ( GTI) (2.97%), Southwestern Energy ( SWN) (2.90%), and Tenneco ( TEN) (2.88%), while a fund like the Market Vectors Global Alternative Energy ETF ( GEX) features hefty shares in Vestas Wind Systems (10.59%) and First Solar ( FSLR) (7.71%). GE) . It is accurate to list all these companies as such, but when one observes a 36.5% industrial weighting in PowerShares WilderHill Clean Energy ( PBW) (PBW) and 42.9% in PUW, it could really mean a variety of companies. This can happen across other sectors as well, and it means you cannot simply compare sector allocations to one another in alternative energy funds. You need to delve deeper into the subsectors, or even take a look at the individual holdings within the fund, in order to understand the inner workings of the ETF. All in all, this demonstrates a need for investors to do their homework.