Marcus, a GS-12 at a Defense Logistics Agency office, was three weeks from his 55th birthday when a coworker leaned over a cubicle wall and said, "You know Fidelity has zero-fee index funds now, right? Why are you still paying TSP fees?"

Marcus didn't have a good answer. He went home, pulled up his statement, and started comparing numbers. That's a smart instinct. It's also a comparison that is easy to get slightly wrong.

The Numbers Side by Side

TSP's expense ratios have hovered around five hundredths of one percent, or roughly 0.05%, for years. The exact figure changes annually and varies a bit by fund, so check tsp.gov for the current year's numbers. On a $100,000 balance, that's about $50 a year.

Commercial index funds vary:

  • Fidelity's ZERO funds charge 0.00%.
  • Fidelity 500 Index and Schwab S&P 500 Index run around 0.015% to 0.02%.
  • Vanguard's Admiral Shares of its 500 and Total Stock Market funds sit near 0.04%.
  • Typical actively managed funds in a workplace plan or brokerage account often run 0.50% to 1.00% or more.

So yes, a few commercial funds beat the TSP on sticker price. But we're talking about the difference between $50 a year and $0 to $20 a year on that $100,000. Nobody retires early because of that gap.

Where the Real Money Is

The meaningful comparison isn't TSP versus Fidelity. It's TSP versus the average fund most investors actually end up holding.

Take a $400,000 balance growing at a hypothetical 6% a year before fees for 20 years. At a 0.05% expense ratio, that grows to roughly $1.27 million. At 0.60%, a common figure for actively managed funds, it grows to about $1.16 million. The difference is around $125,000, and that comes from one decision made once and never revisited.

Now compare 0.05% to 0.02%. On the same $400,000, you save about $120 a year. Over 20 years, even with compounding, that's a few thousand dollars at most. It's real money, but it shouldn't drive a major decision.

The fee gap that matters is measured in tenths of a percent. The one between TSP and the cheapest index funds is measured in hundredths.

What the TSP Expense Ratio Actually Covers

Here's a detail that gets lost in these debates. The TSP's expense ratio is the all-in cost. It folds together administrative expenses and investment management fees, net of forfeitures and certain offsets. There are no sales loads, no trading fees, no account maintenance fees, and no minimums to buy or sell within the plan.

Commercial funds can look cheaper at the fund level while the account around them adds costs. Some brokerages charge for certain trades or for non-core funds. Some advisors layer an annual management fee of 0.75% to 1.25% on top of the funds they pick. That fee often doesn't appear on a fund fact sheet, so people overlook it.

If you're comparing, ask for the total annual cost of the whole arrangement, not just the fund's ratio.

Not Every TSP Fund Has a Twin

The comparison gets murkier once you look past the C Fund.

C Fund. It tracks the S&P 500, so it's easy to match. Any S&P 500 index fund is a close substitute, and tracking differences are tiny.

S Fund. It follows the Dow Jones U.S. Completion Total Stock Market Index, which is basically everything in the U.S. market except the S&P 500. You can approximate it with a commercial extended-market fund, though costs vary.

I Fund. It tracks the MSCI EAFE index, covering developed markets outside the U.S. and Canada. It leaves out emerging markets. A commercial total international fund will include them, which means you'd be holding something different, not just something cheaper.

F Fund. It tracks the Bloomberg U.S. Aggregate Bond Index. Commercial equivalents exist at similar costs.

G Fund. This one has no commercial counterpart. It invests in special-issue Treasury securities that pay an interest rate tied to long-term Treasuries, with no risk of principal loss. You can't buy that at a brokerage. For many federal employees nearing retirement, that's a stable, valuable piece of the portfolio that a bond fund can't fully replicate, because bond funds can lose value when rates rise.

The Catch With Moving Money

Can you just shift your TSP into commercial funds? Mostly, no, not while you're still working. Current employees can't roll money out of the TSP to an IRA while in service, except in limited cases such as in-service withdrawals after age 59½. Separated or retired participants can roll over freely, and that's where the real decision happens.

TSP also offers a mutual fund window, which lets participants invest part of their balance in a broad menu of outside funds. It comes with an enrollment fee, an annual fee, and each fund's own expenses, and the details change, so read the current terms at tsp.gov before deciding it's a bargain.

When Leaving the TSP Makes Sense

Marcus eventually worked through this logic, and it's a reasonable framework:

Reasons to stay. Ultra-low costs, the G Fund, simple lifecycle funds, no sales pitches, and easy withdrawal options. The TSP also lets you buy a annuity through its own program, which you can compare against commercial options.

Reasons to leave. You want a specific asset the TSP doesn't offer (real estate funds, emerging markets, dividend strategies, individual stocks). You want to consolidate accounts with a spouse. You prefer a particular withdrawal setup that the TSP doesn't support, such as more flexible partial payments. Or you want to convert some money to a Roth IRA on your own timeline.

Reasons that sound good but aren't. Saving 0.03% in fees. A coworker's enthusiasm. A seminar promising "better returns" without naming the fee.

What Marcus Decided

He kept most of his money in the TSP. He moved nothing out while still employed, and he plans to revisit the question at separation, when a rollover becomes possible. In the meantime, he opened a small Roth IRA at a low-cost brokerage for international exposure beyond the I Fund's scope. His total blended cost stayed under 0.06%.

That's a boring outcome, and boring is usually what low-cost investing looks like.

A Quick Checklist Before You Switch Anything

  1. Get the current TSP expense ratios from tsp.gov.
  2. Find the all-in annual cost of any alternative, including advisory fees and trading charges.
  3. Confirm the new fund tracks the same index, or know exactly how it differs.
  4. Check the tax effects of any rollover, especially if you hold Roth TSP money.
  5. Look up current contribution and income limits for IRAs at irs.gov, since they change yearly.

This article is general education, not personalized advice, so if your situation involves large balances, a pension, or complicated tax issues, a fee-only planner who works with federal employees can be worth an hour of their time.

The TSP isn't the cheapest option available in every case. It's close to the floor, and it comes with features you can't buy elsewhere. Chasing the last few hundredths of a percent rarely pays. Avoiding the 0.50% and above traps almost always does.