U.S. investors are very much keen on investing in exchange-traded funds (ETF) that hold cryptocurrencies, a new survey commissioned by financial services giant Charles Schwab showed on Thursday.

Some 45% of respondents said they plan to invest in crypto via ETFs over the next year, up from 38% a year earlier, surpassing demand for bonds and alternative assets. Only U.S. equities fared better, with 55% of participants planning to invest.

Among millennial ETF investors, though, crypto was the leading asset class, with 62% saying they plan to allocate to that sector versus only 48% for U.S. stocks, 47% for bonds and 46% for real assets such as commodities.

Boomer ETF investors were much less keen on digital assets, with only 15% of the respondents having plans to invest.

"Pretty stunning," Eric Balchunas, senior ETF analyst at Bloomberg Intelligence, said about crypto's high ranking in investment plans in the survey.

The implications of the survey, which asked 2,200 individual investors between the age of 25 and 75 with at least $25,000 to be invested, could be a boost for the nascent and growing class of crypto-focused ETFs, which are being marketed as a diversification tool for traditional investment portfolios of stocks and bonds.

While U.S.-listed spot bitcoin ETFs hardly need the help, having attracted nearly $19 billion of net inflows since their debut in January, spot ether ETFs have languished on a relative and absolute basis since their launch a few months later. Exits from the incumbent Grayscale Ethereum Trust have overwhelmed inflows into the newer entrants, with net outflows for the group as a whole topping more than $500 million, according to Farside Investors.