The Guggenheim Solar ETF’s (NYSEArca: TAN) seemingly indomitable run continues Friday as the ETF is up 1.1% on volume that has already eclipsed the trailing three-month average of 297,400 shares. Nearly 351,000 shares of TAN have already changed hands.

In just the past month, TAN is up nearly 26%. Last week, TAN got a lift after Elon Musk’s SolarCity (NasdaqGM: SCTY) projected 90% installation growth. SolarCity is TAN’s second-largest holding at 5.72%. [Solar City Boosts Solar ETF]

First Solar (NasdaqGM: FSLR), the largest U.S.-based solar company, is aiding TAN’s ascent. Shares of First Solar are soaring 8% on volume that is already more than 25% above the daily average. Arizona-based First Solar is TAN’s third-largest holding at 5.5% of the fund’s weight.

One catalyst for First Solar may be  new out Thursday that it has entered into an agreement to construct a 250 megawatt (MW)AC solar power plant in Riverside County, California, for a subsidiary of NextEra Energy Resources (NYSE: NEE), according to a statement.

TAN’s rival, the Market Vectors Solar Energy ETF (NYSEArca: KWT), is also flirting with a new high today. That ETF has a 7.5% weight to First Solar.