The best sustainable ETF depends on a distinction most guides skip: ESG funds and clean energy funds are not the same product. A broad ESG fund like ESGV or ESGU holds a screened version of the whole US market — it behaves much like a normal index fund. A clean energy fund like ICLN or TAN is a concentrated sector bet that can fall 40% in a year the wider market rises. Buying the second while expecting the first is the most common mistake in this category.
This guide compares the largest funds in both groups as they stand in 2026, explains which one fits which goal, and covers what to check before buying — including the greenwashing problem that makes two funds with the same label hold very different companies.
Expense ratios and assets change; the structural differences do not. Verify current figures with the issuer before investing.
| Fund | Type | Expense ratio | What it actually holds |
|---|---|---|---|
| ESGV — Vanguard ESG U.S. Stock | Broad ESG | 0.09% | The FTSE US All Cap Choice Index: large, mid and small-cap US stocks with controversial activities excluded. Around $13bn in assets — the largest in the category |
| ESGU — iShares ESG Aware MSCI USA | Broad ESG | 0.15% | MSCI USA with ESG screening applied while staying close to the parent index's sector weights |
| SUSA — iShares MSCI USA ESG Select | Broad ESG, stricter | — | MSCI USA ESG Leaders: only the highest-rated companies within each sector. More selective than ESGU, and more concentrated as a result |
| VSGX — Vanguard ESG International | Broad ESG, ex-US | — | The same screens applied to developed and emerging markets outside the US. Around $6.5bn |
| ICLN — iShares Global Clean Energy | Clean energy | 0.39% | About 152 holdings across global renewable generation and utilities. Around $3bn — the most liquid of the sector funds |
| QCLN — First Trust Clean Edge Green Energy | Clean energy, broader | 0.59% | Adds electric vehicles and power semiconductors to generation. Historically more volatile than ICLN (roughly 33% versus 31% annualised) |
| TAN — Invesco Solar | Solar only | — | A pure solar bet with high beta. The narrowest and most volatile option here; suited to tactical positions, not core holdings |
The two categories answer different questions, and the search terms people use blur them constantly.
ESGV, ESGU, SUSA and VSGX start from a standard market index and remove or underweight companies that fail certain screens — typically weapons, tobacco, thermal coal and severe controversies. What remains still looks like the market: the largest holdings are usually the same technology and healthcare names you would find in any broad fund.
The practical consequence: returns track the wider market closely. That is the point. These are core holdings, not thematic bets, and their expense ratios reflect it — ESGV's 0.09% is close to a conventional index fund.
ICLN, QCLN and TAN hold companies whose business is renewable generation, equipment or related technology. That is a narrow slice of the economy, heavily exposed to interest rates — these are capital-intensive companies whose valuations fall hard when financing costs rise — and to policy decisions in a handful of countries.
The practical consequence: these funds can move violently in both directions and diverge from the market for years. They belong in the satellite part of a portfolio, sized accordingly. How much you put in one matters more than which one you pick, and we cover that arithmetic in position sizing and the risk of ruin.
| If you want to… | Reasonable choice | Why |
|---|---|---|
| Replace your core US equity holding with a screened version | ESGV | Lowest cost, broadest coverage, behaves like the market |
| The same, but with stricter screening | SUSA | Only sector leaders on ESG ratings, at the cost of concentration |
| Add international exposure with the same screens | VSGX | Developed and emerging markets outside the US |
| Take a position on the energy transition | ICLN | The most diversified and liquid of the sector funds |
| The same, including EVs and semiconductors | QCLN | Wider definition of the theme, higher volatility |
| A tactical bet on solar specifically | TAN | Pure exposure, highest risk — a trading position, not a holding |
«ESG» has no single legal definition, and two funds with near-identical names can hold different companies because they apply different screens from different rating providers. The only reliable check is to open the fund's holdings list and read the top twenty. If the names surprise you, the screen is not what you assumed.
Clean energy indices are small universes. A fund with 150 holdings can still have a third of its assets in ten companies, so a single regulatory decision or a disappointing quarter from one manufacturer moves the whole fund.
Renewable projects are financed with debt and sell output on long contracts. When rates rise, both the financing cost and the discount applied to future cash flows work against them at once. This is why clean energy funds fell sharply during the 2022-2023 tightening cycle while broad ESG funds barely diverged from the market.
The gap between 0.09% and 0.59% looks trivial and is not: on a long holding period it is a meaningful share of the return. Pay it when you are buying access to something genuinely different, not for a screened version of an index you could hold for a tenth of the price.
Sustainable mutual funds cover much the same ground with three differences that matter: they price once a day rather than trading continuously, they often carry higher ongoing charges, and some are actively managed rather than tracking an index. For most investors an ETF is the simpler instrument. A mutual fund makes sense mainly when it is the only vehicle available inside a workplace pension or when you specifically want active management of the screens.
What are the best ESG ETFs in 2026?
For a core holding, ESGV and ESGU remain the default choices on cost and coverage; SUSA suits stricter screening. By assets, Vanguard's ESGV is the largest broad ESG equity ETF, at roughly $13bn. Among clean energy funds, iShares' ICLN is the biggest at around $3bn — which also makes it the most liquid and the cheapest to trade.
Are green ETFs a good investment?
As a core holding, broad ESG funds are a reasonable substitute for a conventional index fund at a similar cost. As a bet on the energy transition, clean energy funds have been volatile and highly rate-sensitive; they can be a legitimate satellite position, but they are not a defensive one.
What is the difference between ESG and sustainable investing?
In practice the terms are used interchangeably by fund providers. ESG usually refers to a screening methodology applied to a broad universe; sustainable or thematic investing more often means selecting companies whose business itself addresses an environmental goal. The label matters less than the holdings list.
Do sustainable ETFs underperform?
Broad ESG funds track their parent indices closely, so differences tend to be small and driven mostly by sector weights rather than by the screening itself. Clean energy funds are a different question: they have gone through long stretches of both sharp outperformance and severe underperformance, which is what a concentrated sector bet does.
What is greenwashing in ETFs?
Marketing a fund as environmentally responsible when its holdings do not support the claim. The defence is mechanical: read the top holdings and the exclusion criteria in the fund documentation before buying, rather than relying on the fund's name.
This article is general information, not personalised investment advice. It does not take into account the financial situation, objectives or risk tolerance of any individual reader, and the same text is distributed to all readers. The author holds no position in any fund mentioned. Expense ratios and assets under management change: verify current figures with the issuer before investing. Capital is at risk and past performance does not indicate future results.