NEW YORK ( TheStreet) -- Renewable energy has been one of the most complicated market segments in which to invest for many years. The reason for this is perhaps counter-intuitive but can be understood.In general terms, when the price of oil goes up it creates the sentiment that the world needs more renewable energy sources and infrastructure to offset higher oil or natural gas costs and so prices for wind and solar stocks goes up. When the price of oil goes down, it creates the perception that there is less need for renewable energy and so the price for wind and solar stocks goes down. The price of crude oil peaked in the summer of 2008 at $147. Despite being up 15% year to date, it is still down almost one third since that 2008 peak. Since the peak in crude, the Guggenheim Solar ETF ( TAN) is down 87% and the First Trust ISE Global Wind Energy Index Fund ( FAN) is down 63%. Against the backdrop of crude oil's rally this year, however, TAN is up 92% and FAN is up 44%. The performance dispersion between the two funds has to do with their respective constituencies. TAN is 80% technology stocks and 20% industrial stocks and all of the holdings are pure solar plays. FAN allocates 57% to utilities and some other companies like General Electric ( GE) that might be big players in the industry but for whom the industry barely moves the needle. Next Era Energy ( NEE) is the old Florida Power & Light, but is heavily involved with transmitting wind power to its customers. NEE is a legitimate holding in the fund but does not capture the production of turbines like Danish company Vestas Wind -- FAN's second largest holding -- does. For five years, Vestas is down 80% but is up 289% year to date while NEE is up 41% for five years and 14% in 2013. Renewable energy is evolving to become more important to business. Both Apple ( AAPL) and Google ( GOOG) are investing into the space. Google just announced that it bought 240 megawatts from a wind farm near Amarillo, Texas, to help power its data center in Oklahoma starting in 2014. Apple has bought a third-party renewable energy and built a solar farm, both in North Carolina, to help power its data center in that state.