U.S. investors stung by the falling euro who want to stay invested in Europe are turning to exchange-traded funds designed to strip out the impact of the region's currency.

The biggest among so-called "currency-hedged" ETFs, the WisdomTree Europe Hedged Equity ETF, has already added some $576 million in new money since last Friday and nearly $1 billion since the start of the year, ETF.com data show.

"Currencies have become a huge part of global equity returns," said Art Laffer Jr., a Nashville-based investment manager who uses a currency-hedged ETF for his exposure to Germany.

A currency-hedged ETF strips out the foreign currency return of a given fund by investing in foreign currency forward contracts and rolling them, typically on a monthly basis. This can have a major impact on returns for U.S. investors in a region like Europe, where the euro has dropped dramatically.

The WisdomTree hedged Europe ETF, for example, is up some 8.7 percent year-to-date, compared to some of the biggest unhedged Europe ETFs––the Vanguard FTSE Europe ETF and the iShares Europe ETF––which are both up about 1.1 percent this year.

On Friday, the euro dropped to an 11-year low against the dollar, after the European Central Bank announced on Thursday it would inject a trillion euros into the euro zone to revive a sluggish economy. It has fallen nearly 7 percent against the dollar so far in January, on track for its worst monthly performance in more than three years.

Among other currency-hedged funds that are outperforming their unhedged counterparts, the Currency Hedged MSCI EMU ETF is up 7.6 percent year-to-date, far more than the 1.1 percent for the unhedged iShares MSCI EMU ETF. The iShares
Currency Hedged MSCI Germany ETF is up about 8.7 percent year-to-date, outperforming the 2 percent gain for the unhedged iShares MSCI Germany ETF.

Major U.S. ETF providers such as BlackRock Inc, WisdomTree Investments and Deutsche Bank AG have all been rolling out new currency-hedged funds over the past year to take advantage of the money that has been flowing into the ETFs.

WisdomTree's HEDJ, for example, was one of the biggest ETF asset gatherers last year, adding $5 billion in new money and growing its assets nine-fold over the year.