Two Korean companies make the same high-voltage grid equipment for the same shortage. In the second quarter of 2026 one of them sold ₩1,687.0bn of it and the other sold ₩1,141.8bn.

The bigger one earned less money.

Hyosung Heavy Industries Corporation (KRX:298040) reported operating income of ₩264.3bn on that revenue. HD Hyundai Electric reported ₩287.0bn on 32% less. Hyosung is the larger company by sales and the smaller one by profit, and the gap has persisted for years.

The Whole Difference Sits At The Gross Line

Operating margin in the quarter: 15.67% at Hyosung, 25.14% at HD Hyundai Electric. A gap of 947 basis points.

Now split it. Gross margin was 23.65% at Hyosung and 33.63% at HD Hyundai Electric, a gap of 998 basis points. Selling, general and administrative expense was 6.91% of revenue at Hyosung and 8.49% at HD Hyundai Electric.

So Hyosung actually runs a leaner overhead. It spends 158 basis points less of every won of revenue on running the company. The entire operating margin shortfall, and slightly more, comes from what it costs to produce what it sells.

That distinction matters because it rules out the easy explanations. This is not a company with a bloated cost base or a weak sales organisation. It is a company whose revenue mix includes something structurally less profitable than transformers.

Which Means It Is Mix

Hyosung Heavy has two divisions that share almost nothing. One makes power transformers, reactors and switchgear, selling into the United States from a Memphis plant and into Australia and the Middle East. The other builds apartments and commercial property in Korea under the Harrington Place brand.

Korean residential construction runs at low single-digit gross margins in a good year, and the last three have not been good years. Blending that into a transformer business earning north of 30% at the gross line produces exactly the arithmetic above.

I should be clear that the segment split is not in the summary financials I am working from, so this attribution is inference rather than something I can point at in a table. The half-year report carries the segment note and would settle it. But the structure of the gap, all of it in cost of revenue with none in overhead, is difficult to explain any other way at a company with these two businesses.

The construction division also produced a more concrete cost recently. On July 31 the company assumed ₩346.3bn of project finance debt after missing a responsible completion deadline on a Seoul development, an amount the filing scores at 13.91% of consolidated equity. That is what a low-margin business with contingent guarantees attached looks like when one of the guarantees is called.

And Yet The Earnings Multiple Is Higher

Here is what makes this interesting rather than simply a case for owning the other one.

At the August 27 close of ₩3,079,000, up 10.08% on the day, across 9,324,548 shares, Hyosung Heavy is capitalised at ₩28.71tn. Equity at June 30 was ₩2,728.8bn, so the shares trade at about 10.5 times book. First-half net income of ₩263.1bn annualises to ₩526.1bn, which puts the price near 55 times earnings.

HD Hyundai Electric closed at ₩821,000 for a ₩29.59tn market capitalisation against ₩2,258.3bn of equity, so 13.1 times book, and about 36 times annualised first-half earnings.

Two similar-sized market capitalisations. Hyosung is cheaper on book and considerably more expensive on earnings. The market is paying more per won of current profit for the company with the lower margin, the weaker balance sheet and the construction division.

The Bull Case Is The Slope

There is a coherent argument for that, and it is about direction rather than level.

Hyosung Heavy's operating margin went from 1.48% in FY2020 to 4.08% in FY2022, 5.99% in FY2023, 7.41% in FY2024, 12.52% in FY2025 and 15.67% in the second quarter of 2026. It is still climbing steeply. Operating income in the first half of 2026 was ₩416.6bn against ₩266.6bn a year earlier, up 56.1%.

HD Hyundai Electric's margin went 20.14%, 24.40%, then 25.14%. It has largely plateaued, which is what you would expect from a company that got there first.

So the case is that Hyosung is three or four years behind on the same curve and has further to travel. If its grid division reaches the margins its rival already earns, and the construction drag stays constant rather than growing, the blended margin has room to move several more points. On that path today's 55 times earnings compresses fast.

The case against is that the construction division is not a constant. It just cost 13.91% of equity. Korean contractors typically carry several completion guarantees at once, and the half-year report's contingent liabilities note is where the rest sit. A business that can produce a ₩346.3bn liability without warning is not a fixed drag; it is a variable one with a fat tail.

The balance sheet compounds it. Cash was ₩172.6bn at June 30 against current liabilities of ₩4,919.0bn and current assets of ₩4,644.1bn, so working capital was already negative before the debt assumption landed on August 1. HD Hyundai Electric had ₩988.1bn of cash and positive working capital.

What To Watch

Gross margin, quarter by quarter, against the rival's. It was 23.65% versus 33.63% in the second quarter. Narrowing would mean either the grid division is catching up on pricing or construction is shrinking as a share of the mix, and either supports the higher multiple. A stable ten-point gap through 2027 would mean the mix is the mix, and paying more per won of earnings for the diluted version stops making sense.

The second marker is the segment disclosure in the FY2026 annual report, due next March. It gives the revenue and operating profit of the grid business separately. If that division alone is running near 25%, the market is right to value Hyosung on what it will become rather than on what it currently reports.