With skyrocketing oil prices and growing environmental concerns, there is increasing focus on eco-friendly companies, and ones that work to develop renewable energy sources. These companies run across the spectrum, so if you are looking to add some green to your investments, the best way could be through green-oriented funds. Let's dive into the best of the bunch.

Calvert Large Cap
If you're looking to invest in the big names, but still want to be environmentally friendly, the Calvert Large Cap Growth Fund (CLGAX) could be a good start. The fund screens for and invests in large cap stocks that have reputations for being conscious of the environment. Calvert's top holdings include Apple (Nasdaq:AAPL), Amazon (Nasdaq:AMZN) and AT&T (NYSE:T), so you still get good exposure to the market's big-name stocks. The fund is well-diversified and has produced solid returns, beating the S&P 500's average return over the last five years, and it has a 13.19% return year-to-date.

Spectra Green
Calvert's fund looks nice, but if you want that strategy, I have to say that like the Spectra Green Fund (SPEGX) even better. This fund has the same objectives as Calvert, but has earned almost 17% average returns over the last five years and 18.7% year-to-date. This year's performance is quite impressive, considering the S&P 500 is only up around 10%.

The fund looks even more diversified than Calvert, which is how the fund was able to produce those big returns even with its top holding, Starbucks (Nasdaq:SBUX), down 26% for the year.

Guinness Atkinson Alternative Energy
Want more exposure to alternative energy? This is an area that has been very hot recently, and the next two funds deserve a look. The first, Guinness Atkinson Alternative Energy Fund (GAAEX) has only been around since March 2006, but has already produced impressive returns. After a large dip soon after the funds inception, it has recovered nicely, now posting nearly 16% annualized returns since inception. If you bought after the dip you fared much better; the fund's value is up more than 50% over the low point from last year.

New Alternatives
Another great alternative energy fund (that has more of a track record) is the New Alternatives Fund (NALFX). This fund has been under the management of David Schoenwald since 1982, and it has been performing well pretty much ever since. Over the last five years, the fund has produced 22.04% average returns, and is up over 30% year to date. Typically, alternative energy companies are generally small caps, which can produce bigger returns, but can also be more risky. The two things you need to combat the risk are diversification and knowledge of the industry. Those are the two biggest benefits of mutual funds over individual stocks, and these funds certainly have plenty of both.

The Best of Both Clean Worlds
I like to save the best for last - Winslow Green Growth (WGGFX) provides investors with a mixed portfolio of both eco-friendly companies and companies involved in specifically helping the environment. The results speak for themselves, with five-year annual returns of 26.8%. This is another small-cap fund, with top holdings including First Solar (Nasdaq:FSLR) and Green Mountain Coffee Roasters (Nasdaq:GMCR). The investment team has been led by Jackson Robinson since 1994, and has produced consistent returns. After an amazing year in 2003, the fund has been providing stable 12% gains each year after. This is a very well regarded fund, with a five-star rating from Morningstar. I think it is positioned for continued success.

The Bottom Line
Green investing is becoming bigger and bigger, but this isn't a fad. As the cost of oil keeps rising, demand for alternative energy will steadily increase. The same can be said for eco-friendly companies. Concerns are growing about the environment.

Believe it or not, many people factor in whether a company is a ruthless corporation or is respectful of its footprint on the planet when making both investing and consumer decisions. All of the above mentioned funds are potentially great ways you can grow your money, while feeling good about the companies you're supporting at the same time.

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