A portfolio of $1 million by retirement may no longer be enough to live comfortably, according to a recent study from insurance company Northwestern Mutual. Instead, many Americans now believe that they might need around $1.5 million to have a comfortable retirement. In 2020, the number was much lower, at just $951,000.

It shouldn't come as too much of a surprise that more money is likely necessary for retirement, given the fast pace of inflation over the past few years. But a huge 50-plus-percent increase in just four years is alarming nonetheless.

Ultimately, everyone's magic number for retirement may vary. Not everyone has the same lifestyle, and where someone decides to retire will also have a significant effect on their financial needs. The conclusion, however, remains the same: You should try to save as much as you can for retirement.

A great ETF to invest in for the long haul

Investing in an exchange-traded fund (ETF) is a good way to simplify your investing strategy. It can also minimize the need for you to constantly monitor your investments. And while there may be some ambiguity about where the world may be in 10 or 20 years, one thing seems certain: There will be more connected devices, and a greater reliance on technology.

Based on that assumption, one ETF that can make for a solid long-term investment is the VanEck Semiconductor ETF (SMH -0.84%). Semiconductors are essential parts of electronic devices and are growing more important in the world as more devices become connected to the internet. The VanEck Semiconductor ETF invests in companies involved with semiconductor production and equipment, focusing on leading companies within the industry.

The top three stocks in the fund are all big names in tech: Nvidia, Taiwan Semiconductor Manufacturing, and Broadcom. Collectively, they account for 41% of the fund's total portfolio. By concentrating on market leaders, the fund has the potential to be a great way to invest in semiconductors.

Could the fund grow your portfolio to $1.5 million?

Thanks to the strong returns Nvidia has generated in recent years, the ETF has been a top-performing fund. In 10 years, it has generated total returns (including dividends) of more than 1,000%. That averages out to a compound annual growth rate (CAGR) of 27%. That dwarfs the S&P 500's returns over that time frame, which total just 229% when including dividends, for a CAGR of 12.6%.

While generating 27% returns over decades may not be sustainable, investors may still be able to generate market-beating returns given the promising growth prospects in semiconductors. Analysts from Fortune Business Insights project that between 2022 and 2029, the semiconductor market will grow at a CAGR of 12.2%. And in the long run, the growth rate may accelerate even higher.

Assuming the ETF can generate 15% annual returns in the very long run, over a 30-year period, investors could potentially see their investments grow to 66 times their value. That means that for an investment to get to $1.5 million, you would need to invest about $23,000 today. But if it's over a shorter time frame or the average return is lower, the investment amount would need to be higher. If the return was 14% and the investment period was 25 years, then you would need to invest around $57,000 for your portfolio to be worth $1.5 million.

There does appear to be the potential for the VanEck Semiconductor fund to be able to grow an investment to $1.5 million, but it'll take time, and it could take a sizable investment today.

Investing in ETFs can be an easy way to grow your portfolio

It's impossible to know what your actual long-run return will be from any ETF. But that doesn't change the fact that investing in a growth-focused fund can be an excellent way to grow your portfolio's balance and make for a better retirement in the long run.

ETFs can take much of the guesswork out of investing. Whether you want a narrowly focused fund, such as the VanEck Semiconductor ETF, or a broader one that factors in all the stocks on the S&P 500, there are many options out there for you to consider.