Few U.S. chief executive officers are as hot as Elon Musk these days. Musk is the CEO of not one, but two of the highest flying publicly traded companies in the U.S. SolarCity (SCTY), the maker of solar energy systems for business and residential customers, has seen its shares more than double in the past month.

Musk's other company, electric car maker Tesla (TSLA) is up about 74 percent in the past month. Indeed, it is a good time to be Elon Musk and it is has been a good time for his fans that have bought shares of SolarCity or Tesla.

Despite the popularity of Musk and his companies, accessing both stocks via one ETF is currently difficult. One ETF can be considered the Tesla ETF, that being the First Trust NASDAQ Clean Edge Green Energy Index Fund (QCLN). QCLN allocates over 15 percent of its weight to Tesla.

Solar City for all its bullishness is not even included among the Market Vector Solar Energy ETF's (KWT) 34 holdings, but the larger Guggenheim Solar ETF (TAN) does feature an almost 5.7 percent weight to the stock. Neither ETF features Tesla, however.

Investors looking for exposure to both stocks via one ETF should consider a fund that has been called the Elon Musk ETF. That ETF is the PowerShares WilderHill Clean Energy Portfolio (PBW).

While the weights are not staggering, SolarCity and Tesla are PBW's two largest holdings at weights of 4.75 and 4.74 percent, respectively. Based on Wednesday's closing prices, buying one share each of SolarCity and Tesla would cost about $131. Admittedly, this is should not be a deciding factor in making investment decisions, but for $131, investors can get about 24 shares of PBW.

Indeed, PBW did not have a good Wednesday, falling by almost 4.3 percent. However, the impact of SolarCity and Tesla on this ETF is palpable as the fund has surged over 25 percent in the past month. Of course, soaring solar stocks are part of the reason PBW has performed so well.

The ETF features a significant allocation to the solar space with names such as First Solar (FSLR), Trina Solar (TSL) and SunPower (SPWR) found among the ETF's top-10 holdings.

Until other alternative energy ETFs rebalance to include larger weights to both SolarCity and Tesla, PBW will reign as the Elon Musk ETF. It appears some investors are already buying into that concept as PBW has hauled in almost $10.1 million of its $177.9 million in assets in just the past month, according to PowerShares data.

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