The three retirement accounts you need to maximize

The median U.S. household has just $87,000 in retirement savings, according to research by The Motley Fool. With the diminishing aid of pensions and Social Security, this leaves many younger Americans in a vulnerable position.

But with some effort, the younger workers of today can save more for retirement today.

There isn't one clear-cut way to save for retirement, but it's not going to happen by stashing away money in a low-interest savings account. You have to invest to reach your retirement goals, and there are three main accounts that allow you to grow your wealth through the market, while offering special tax benefits.

1. 401(k) account

A 401(k) is an account offered by employers that allows you to invest pre-tax money for retirement. In some cases, your employer may even offer a dollar-for-dollar match up to a certain limit. It's essentially "free money" to incentivize you to save.

The IRS puts yearly limits on how much you can invest in a 401(k). And the accounts comes with a few stipulations:

• If you withdraw money before 59½, you'll be hit with a 10% penalty. There are some exceptions, including qualified medical expenses, a birth or adoption, college tuition and for first-time homebuyers.
  
• When you start withdrawing, you'll need to pay ordinary income tax on the money.
  
• If you don't touch your 401(k), you still have to take required minimum distributions (RMDs) starting the year you turn 73. RMDs are not a set dollar amount. Rather they're a sliver of your total retirement accounts, based on your life expectancy according to the IRS.

2. IRA

An IRA, or independent retirement account, is opened and maintained by the saver and is not connected to their workplace. That means you can keep investing in an IRA, even after you switch jobs.

Another standout benefit is enjoying tax-free growth on your investments, so you won't be taxed on dividends or capital gains while the investments are in your account.

IRAs are easy to set up and accessible, offered at most banks and credit unions, as well as through online brokers and investment companies. You can set up automatic contributions into your IRA from your checking or savings account.

And unlike your employer's 401(k) plan, you can choose your investments with an IRA and many brokerage firms or banks will help guide you depending on your timeline to retirement.

If you already have a 401(k) plan through your employer, an IRA is an effective way to supplement your retirement savings. There are two main kinds of IRAs: Traditional IRAs and Roth IRAs.

With traditional IRAs, you delay paying taxes until you withdraw funds in retirement. With Roth IRAs, you give the IRS its share up front and contribute after-tax dollars. As long as your account has been open for five years, your withdrawals are tax-free.

Traditional and Roth IRAs have the same contribution limits, which are set annually.

Generally, traditional IRAs are most effective if you expect to be in a lower tax bracket when you retire, while Roth IRAs are best if you expect to be in a higher tax bracket when you retire.

Overall, the rules around withdrawing early from an IRA are more lenient with Roth IRAs than with traditional IRAs.

Traditional IRAs: If you withdraw funds from your traditional IRA before 59 1 and a half, you are taxed at your current income tax rate and you are charged a 10% early withdrawal penalty fee.

Roth IRAs: Penalties on withdrawing from your Roth IRA before age 59 and a half depends on whether it's your contributions or your earnings that you're tapping into. Withdrawing contributions from your Roth IRA at any age is tax- and penalty-free. Withdrawing earnings early, however, incurs a 10% early withdrawal penalty and you may be subject to income taxes.

Like 401(k) accounts, first-time home purchases, college expenses and birth or adoption expenses count as exceptions to the early withdrawal penalty.

If you want hands-off investing, open a Roth IRA with a robo-advisor that can create a custom portfolio based on your risk tolerance and retirement date. Some of the best robo-advisors, like Wealthfront, Betterment and SoFi Invest®, adjust your investments as you get closer to your target returement date.

3. Health Savings Account (HSA)

A Health Savings Account allows individuals with a high deductible health plan (HDHP) to put money away for future medical expenses.

If your employer offers an HSA and you have a HDHP, you can elect to have part of your paycheck taken out pre-tax and put into the account. These funds can be used to reimburse you for qualified medical expenses, or you can invest the money in stocks, bonds or index funds.

As long as you use the funds for medical expenses, your money grows tax-free. If you decide to use this as a retirement account, you will pay ordinary income tax on it, but you can use the money as you'd like.

HSAs are sometimes referred to as "triple tax advantaged," because money goes in tax-free, grows tax-free and can be taken out tax-free .

There are also annual limits on how much you can deposit in an HSA depending on how you file.

Many people have an HSA through their workplace, and your employer may match your contributions or contribute a set amount. You can also open one through a bank like Bank of America, an investment firm like Fidelity or an HSA provider like Lively or HealthEquity.

If you leave your employer and want to switch HSA providers, you can move funds from one account to another. There is typically a form to file and it may take a few weeks for the funds to transfer.

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