) --

PowerShares WilderHill Progressive Energy


has led

PowerShares WilderHill Clean Energy

(PBW) - Get Invesco WilderHill Clean Energy ETF Report

by a wide margin over the past three months. PUW's return was 19.20% compared to only 0.76% for PBW.

Much of the gap between the ETFs came since the end of July, as PUW's return rose 12.2% while PBW rose 1.1%.

The stocks among PUW's top 10 holdings that provided the lift were

Clean Fuels

(CLNE) - Get Clean Energy Fuels Corp. Report

, up about 50%, along with

Owens Corning

(OC) - Get Owens Corning Report


Chesapeake Energy

(CHK) - Get Chesapeake Energy Corporation Report

, up about 30%.


(MEOH) - Get Methanex Corporation Report

also had a portfolio-outperforming return of just under 20%.

PBW's fund had similar returns from its top 10 holdings.

Fuel Systems


had return of nearly 50%, while



gained more than 50%.


(CZZ) - Get Cosan Limited Class A Report


International Rectifier


both gained more than 20%.

On the downside, PUW's worst performing top 10 holdings were flat, while PBW saw

Applied Materials

(AMAT) - Get Applied Materials, Inc. Report



TheStreet Recommends


lost ground.

However, the current top 10 holdings don't tell the entire story. As of June 30, PBW's top 10 was dominated by solar stocks, including

First Solar

(FSLR) - Get First Solar, Inc. Report








JA Solar


. Over the aforementioned period, JASO lost 20%, FSLR lost nearly 15%, and ESLR lost more than 5%.

Broadwind Energy

(BWEN) - Get Broadwind Energy, Inc. Report

, the former No. 1 holding on June 30, fell nearly 25% and went from 3.14% of PBW to 2.52% on Sept. 14.

PUW has seen changes among its top 10 as well, but it more closely resembles its June 30 composition. A couple of stocks moved out of the top 10, including

Southwestern Energy

(SWN) - Get Southwestern Energy Company Report




. However, these were more allocation changes than a price decline, as SWN was flat and USU actually gained 30% over the period.

PowerShares ETFs have performed well in many cases, but investors need to pay attention to the holdings in these funds because they will shift over time -- and that will alter results.

Since PUW's inception in October 2006 (PBW was launched in March 2005), the two funds have tracked very closely, with occasional under- and over-performance, until last fall. From its Nov. 19 low, PUW gained 105% compared to a 71% return for PBW.

Furthermore, PUW failed to breach its low in March, while PBW did decline to a new low.

This pattern of outperformance suggests that the character of the rally favored PUW, or its focus on bridge technologies, ways to improve fossil fuels, and relatively cleaner fossil fuels such as natural gas. That is apparently the winning strategy moving forward.

Jim Cramer has been be

beating the drum

about the strength of natural gas and talking about why it has been unloved in Washington, D.C.

A change in political fortunes would be a boon to a fund such as PUW because it is the fund for the next 10-plus years, and legislation appears to be moving in its favor. Congress will pass some form of "green" legislation, but it won't be as draconian as feared because the public, by a wide and vocal margin, doesn't believe the benefits outweigh the costs.

Meanwhile, at this point, PBW is more like a collection of lottery tickets with a heavy dose of solar. The future is moving in the direction of PBW, but more slowly than investors may like.

Nevertheless, a reversal in energy prices could change the game once again. At $150 a barrel for oil, the technologies in PBW will become much more competitive.

-- Written by Don Dion in Williamstown, Mass.

At the time of publication, Dion did not have positions in any of the funds and equities mentioned.

Don Dion is president and founder of

Dion Money Management

, a fee-based investment advisory firm to affluent individuals, families and nonprofit organizations, where he is responsible for setting investment policy, creating custom portfolios and overseeing the performance of client accounts. Founded in 1996 and based in Williamstown, Mass., Dion Money Management manages assets for clients in 49 states and 11 countries. Dion is a licensed attorney in Massachusetts and Maine and has more than 25 years' experience working in the financial markets, having founded and run two publicly traded companies before establishing Dion Money Management.

Dion also is publisher of the Fidelity Independent Adviser family of newsletters, which provides to a broad range of investors his commentary on the financial markets, with a specific emphasis on mutual funds and exchange-traded funds. With more than 100,000 subscribers in the U.S. and 29 other countries, Fidelity Independent Adviser publishes six monthly newsletters and three weekly newsletters. Its flagship publication, Fidelity Independent Adviser, has been published monthly for 11 years and reaches 40,000 subscribers.