Low cost ETFs are one of the cleanest ways to build a portfolio without handing away too much of your return to fees. The real decision is not just “which fund is cheapest,” but which fund gives you the right exposure, trades efficiently, and fits the account you actually use. Here I break down what drives ETF costs, which fund types usually stay inexpensive, and how I would choose among them in a US portfolio.
The main thing to know before comparing funds
- The expense ratio is the baseline fee, but it is not the whole cost of owning an ETF.
- Broad US stock ETFs often sit around 0.03%, while many core bond and developed-international funds are also very cheap.
- Trading friction, especially bid-ask spread, can matter more than the headline fee on small or less liquid funds.
- For many investors, one stock ETF and one bond ETF is enough to get started.
- The best fund is usually the one that matches your benchmark, stays liquid, and does not create hidden friction.
What makes an ETF truly low cost
When I look at an ETF, I start with the expense ratio because that is the cleanest fee to compare. Investor education resources describe it as the portion of fund assets used each year to pay operating expenses, and those costs are taken out of the fund rather than billed to you directly. That means the fee drags on returns quietly, which is exactly why a small difference matters more than it first appears.
On a $10,000 investment, a 0.03% expense ratio costs about $3 per year. A 0.50% fund costs about $50. The gap is only $47 in year one, but over long holding periods that difference compounds, and it keeps compounding as long as your money stays invested. That is why I care much more about a fund’s ongoing cost than its flashy marketing or short-term performance chart.
One large ETF provider reported an average ETF expense ratio of 0.07% versus an industry average of 0.44% as of the end of 2025, which gives you a good sense of how far low-fee investing has moved in the US market. For broad index exposure, very cheap is now normal, not exotic. Once you understand that, the next step is to look beyond the fee table and check the costs the headline number does not show.
The fees that do not show up in the headline number
The expense ratio is only the starting point. In practice, I also look at the spread, brokerage costs, tracking difference, and tax drag, because those can change the real cost of owning an ETF more than people expect. A fund can look cheap on paper and still be slightly expensive to trade if it is thinly traded or carries a wide bid-ask spread.
| Cost type | What it means | Why I care | How I try to control it |
|---|---|---|---|
| Expense ratio | The annual fee charged by the fund | It is the permanent drag on returns | Compare funds with the same benchmark |
| Bid-ask spread | The gap between the buy and sell price | It is a real trading cost, especially on thinly traded ETFs | Prefer liquid funds and use limit orders when spreads are wider |
| Commission or platform fee | A charge from your broker or trading platform | It can erase the benefit of a tiny fee on small trades | Use commission-free trading where possible and avoid frequent trading |
| Tracking difference | The gap between the ETF and its benchmark over time | It shows whether the fund actually delivers what it promises | Check multi-year results, not just the prospectus |
| Tax drag | Taxes caused by distributions, dividends, or capital gains | It matters most in taxable accounts | Use tax-efficient funds and place bond-heavy holdings carefully |
The practical lesson is simple: a fund with a slightly higher fee but much tighter spreads can be cheaper in real life than the fund with the absolute lowest expense ratio. That is especially true if you trade small amounts, buy less-liquid strategies, or move in and out of positions too often. With that in mind, the next question is which ETF categories usually stay inexpensive without compromising the portfolio’s structure.
The cheapest core funds for a US portfolio
If your goal is broad, long-term investing, the lowest-cost options are usually plain-vanilla index ETFs. In the US, the biggest providers have pushed core funds to the point where 0.03% is common for broad stock and bond exposure. That is a tiny annual charge, and for most investors the difference between similarly built funds will come down to the benchmark, liquidity, and tracking quality rather than the fee alone.
| Role in the portfolio | Example ETFs | Current expense ratio | Why it is useful |
|---|---|---|---|
| US total market | VTI, SCHB, ITOT | 0.03% | One fund can cover most of the US stock market, which keeps the portfolio simple. |
| US large-cap core | IVV | 0.03% | Useful if you want S&P 500 exposure and do not need the smaller-company slice. |
| Developed international stocks | SCHF | 0.03% | Cheap access to non-US developed markets and a cleaner way to diversify away from the US. |
| Emerging markets | SCHE | 0.06% | Still inexpensive, but slightly higher because the markets are more complex and less liquid. |
| US aggregate bonds | BND, AGG, SCHZ | 0.03% | A low-fee way to add stability and income without paying much for the fixed-income sleeve. |
What I like about these core funds is that they solve a real portfolio problem instead of selling a story. They give you broad exposure, low turnover, and a cost structure that is hard to beat without changing the risk profile. If you are tempted by an ETF simply because it is “even cheaper,” the next section is where I would slow down and compare the fund details more carefully.
How I compare similar ETFs before buying
When two ETFs look similar, I do not start by asking which one is cheapest. I start by asking whether they are really trying to do the same job. A fund that tracks a broader index, trades more actively, or handles a less-liquid market can deserve a slightly higher fee if it gives me cleaner exposure and less friction.
| What I check | What I want to see | Why it matters |
|---|---|---|
| Index match | The ETF tracks the exposure I actually want, not a near substitute | A cheap fund is not useful if it misses part of the market I am trying to own. |
| Expense ratio | Competitive within its category | This is the permanent fee drag, so it should be low relative to peers. |
| Liquidity and spread | Tight bid-ask spread and enough daily volume | This lowers the cost of getting in and out, especially for smaller trades. |
| Tracking difference | Small and consistent gap versus the benchmark | It tells me whether the fund actually delivers the index return I expected. |
| Tax treatment | Reasonable distribution profile for the account type | Tax drag matters a lot more in taxable accounts than in IRAs or 401(k)s. |
In a taxable account, I usually lean toward ETFs that keep distributions modest and tracking tight. In retirement accounts, the tax edge matters less, so I put more weight on index quality, liquidity, and how well the fund fits the rest of the portfolio. Those filters also help you avoid the common mistakes that make a cheap ETF look more expensive than it is.
The mistakes that erase the fee advantage
- Buying a niche fund just because the fee is low. The strategy might be narrow, volatile, or built on an index that does not fit your real goal.
- Ignoring the spread on a thin ETF. A tiny annual fee can be overwhelmed by a poor entry price if the fund trades lightly.
- Overlapping too many funds. Owning three ETFs that all hold the same top stocks adds complexity without improving diversification much.
- Chasing yield without looking at the structure. High income can come with more turnover, more taxes, or more credit risk than you intended.
- Trading too often. The more you buy and sell, the more likely you are to turn a low-cost holding into a high-friction habit.
I see this most often with newer investors who focus on the expense ratio as if it were the whole story. It is not. A better habit is to pick a small number of funds that cover the markets you want, then hold them long enough for the fee advantage to do actual work. That naturally leads to the question of what a sensible starter mix looks like in practice.
A simple ETF mix you can actually use
You do not need a dozen funds to build a solid portfolio. In fact, for many US investors, fewer funds means fewer mistakes. I usually think in terms of a simple core with one stock ETF and one bond ETF, then a small international sleeve if the investor wants global diversification.
| Investor profile | Sample mix | Why it works |
|---|---|---|
| Simple long-term growth | 100% US total market ETF | One holding keeps the portfolio easy to understand and automatically diversified across large, mid, and small companies. |
| Balanced long-term investor | 70% US total market ETF, 30% aggregate bond ETF | Lower volatility than an all-stock portfolio while keeping the fee structure very small. |
| More globally diversified | 55% US total market ETF, 25% developed international ETF, 20% aggregate bond ETF | Gives you exposure beyond the US without turning the portfolio into a maintenance project. |
If you want emerging markets exposure, I would usually keep it as a modest satellite position rather than the centerpiece. The fee is still low, but the volatility is higher and the ride is less even than with broad developed-market funds. My view is that a good ETF portfolio should be boring enough to stick with, because consistency usually matters more than trying to optimize every basis point.
What to keep doing after you buy
The real value of a low-fee portfolio comes from what you do after the purchase, not before it. Reinvest dividends automatically if that matches your plan, rebalance on a schedule instead of reacting to every market move, and review costs once a year so a fund’s fee or spread does not quietly drift out of line. If you are buying a less-liquid ETF, use a limit order rather than a market order so you control the price you pay.
- Buy in amounts that make sense for the spread, not just for convenience.
- Rebalance only when the portfolio truly drifts from your target allocation.
- Keep bond funds in the right account when taxes matter.
- Check whether a fund still fits your benchmark before you chase a lower fee elsewhere.
- Ignore short-term noise and let the cost advantage compound.
The point of cheap ETFs is not to obsess over pennies; it is to remove avoidable friction so your money can do the heavy lifting. If you keep the portfolio simple, stay alert to trading costs, and focus on the exposure rather than the slogan, the fee savings become real instead of theoretical.
