A 1 MW UPS assembled in the United States from the parts a US OEM actually buys carries about 17 points of federal duty in its ex-works price. The same UPS imported finished from China carries 55. The “50% copper tariff” that every quote now cites is 3.8 of those 17 points, and on a 3.9 MWh Megapack it is $5,700 on a $1.39 million unit. This piece builds the bill of materials for four products by weight and by value, puts each line on its HTS code and origin, applies the stack in force on October 10, 2025, and shows which layer actually moves the landed cost: the metal content, the Chinese electronics, or the country the finished good ships from.
Source: Open Factory Tariff Exposure Calculator (compiled from HTSUS 2025 Rev. 25 chapter 99, Federal Register proclamations and executive orders; as of October 2025)
The US-assembly base case lands at 17.1 points for the UPS, 12.7 for a six-section 15 kV lineup, 6.7 for a 2 MW enclosed diesel genset and 12.6 for the Megapack, rising to 16.5 when the Chinese battery rate steps up on January 1, 2026. Every rate here is in the Open Factory Tariff Exposure Calculator with its Chapter 99 heading and Federal Register citation; every BOM share that is our estimate says so in the CSV.
Three Bases, Not One Rate
The reason a tariff on electrical gear is a bill of materials and not a percentage is that the six layers in force are assessed on three different bases. Section 232 copper, under Proclamation 10962 of July 30, 2025 (90 FR 37727, effective August 1), is 50% “upon the value of the copper content” of semi-finished copper and a short list of derivatives, and the importer reports that content in kilograms on the entry line. Section 232 steel and aluminum, raised to 50% by Proclamation 10947 (90 FR 24199, effective June 4, 2025), is on full value for chapter 72, 73 and 76 goods and on metal content for derivatives outside those chapters. The IEEPA reciprocal tariff under EO 14257 (90 FR 15041) applies only to the non-metal remainder of a 232 good, per HTSUS chapter 99 U.S. note 2(v). Section 301 and the China fentanyl duty apply to full value and stack on everything.
Source: Open Factory Tariff Exposure Calculator
Six layers, three bases, and one non-stacking order: EO 14289 (90 FR 18907) stops the auto, Canada, Mexico, steel and aluminum actions from piling on each other, and says nothing about Section 301 or the China fentanyl duty, so those two stack on a Chinese good with everything else. A US OEM therefore pays 50% on the copper and steel it imports as metal, and nothing under 232 on the same copper and steel when it arrives inside a finished switchgear section from Monterrey, because 8537.20.00 is on no 232 list as of October 10, 2025. That inversion is the procurement story of this piece, and it is live in every RFQ on a sourcing manager’s desk this quarter. The Tariff Schedule 2026 piece tracks the instruments that can change it.
The Eighteen HTS Lines
The four finished goods sit on four HTS lines: 8504.40.95 for the static converter that is a UPS (column 1 Free), 8537.20.00 for boards and panels over 1,000 V (2.7%), 8502.13.00 for diesel generating sets over 375 kVA (2.0%) and 8507.60.00 for lithium-ion batteries (3.4%), with the BESS statistical suffix 8507.60.00.30 “fully encased within a housing.” Rates are from HTSUS 2025 Revision 25 and match the 2026 Revision 18 schedule line for line. None of the four is on a Section 232 list in October 2025. All four are on Section 301 lists for Chinese origin: List 3 at 25% for the UPS, List 1 at 25% for the lineup and the genset, List 4A at 7.5% for the battery.
Source: Open Factory Tariff Exposure Calculator, USITC HTSUS 2025 Rev. 25
Eighteen lines, four of them finished goods with no 232 exposure and fourteen inputs of which nine carry a 232 heading. The inputs are where the duty attaches for a US assembler: refined copper bar 7407.10.50 and winding wire 7408.11.60 under 9903.78.01 at 50% on copper content, flat steel 7208 and 7210 under 9903.81.87 at 50% on full value, aluminum sheet 7606 under 9903.85.02, and, since the BIS inclusions notice of August 18, 2025 (90 FR 40326) added 407 codes, the instrument transformers of 8504.31, the transformer cores of 8504.90.96, the cable lines of 8544 and the radiators of 8419.50, each at 50% on their steel or aluminum content. The Chinese lines carry USTR’s four-year review (89 FR 76581): semiconductors 8541 and 8542 at 50% since January 1, 2025, and non-EV lithium-ion batteries moving from 7.5% to 25% on January 1, 2026.
| HTS | Description | MFN | Section 232 (Oct 10, 2025) | Section 301 (China) |
|---|---|---|---|---|
| 8504.40.95 | Static converters (UPS) | Free | none | List 3, 25% |
| 8537.20.00 | Panels over 1,000 V (switchgear) | 2.7% | none | List 1, 25% |
| 8502.13.00 | Diesel gensets over 375 kVA | 2.0% | none | List 1, 25% |
| 8507.60.00 | Lithium-ion batteries (BESS) | 3.4% | none | List 4A 7.5%; 25% from Jan 1, 2026 |
| 7407.10.50 | Copper bars and rods (busbar) | 1.0% | 9903.78.01, 50% on copper content | List 3, 25% |
| 7408.11.60 | Copper winding wire | 3.0% | 9903.78.01, 50% on copper content | List 3, 25% |
| 7208 / 7210 | Flat steel | Free | 9903.81.87, 50% on full value | List 3, 25% |
| 7606 | Aluminum sheet | 3.0% | 9903.85.02, 50% on full value | List 3, 25% |
| 8541.29 | IGBT modules | Free | none | 9903.91.05, 50% |
| 8532.25 | Film capacitors | Free | none | List 1, 25% |
| 8504.31.40 | Instrument transformers (CT, VT) | 6.6% | 9903.85.08, 50% on aluminum content | List 3, 25% |
| 8535.90.80 | Vacuum interrupters | 2.7% | none | List 1, 25% |
| 8544.42.90 | LV cable with connectors | 2.6% | 9903.78.01 copper; 9903.85.08 aluminum | List 3, 25% |
| 8419.50.50 | Radiators, heat exchangers | Free | 9903.85.08, 50% on aluminum content | List 1, 25% |
| 8504.23.00 | Transformers over 10 MVA | 1.6% | 9903.81.91, 50% on steel content | List 1, 25% |
Four Bills of Materials by Weight
We built each product two ways: by mass, because the 232 metal layers are declared in kilograms, and by value, because every other layer is ad valorem. The Megapack 2 XL is the only one of the four with a public mass: Tesla’s specification lists 38,100 kg (84,000 lb) for 3,916 kWh and 1,927 kW, and a list price of $1.39 million per unit, which is $355/kWh. For the UPS, the lineup and the genset the OEM sheets we could reach do not publish frame mass, so the unit masses (2,000 kg for a 1,250 kW class frame, 1,400 kg per 15 kV section, 22,000 kg for an enclosed 3516-class package) are our engineering estimates, and the CSV says so on every row.
Source: Open Factory Tariff Exposure Calculator (BOM estimates; Tesla Megapack 2 XL specification)
By mass the lineup is 68% steel and 12% copper, the genset is 80% iron and steel and 4% copper, the UPS is 45% steel and 18% copper, and the Megapack is 64% LFP cells with 15% steel and 3% copper. Multiply the copper shares by the unit masses and the copper in the four products is 360 kg, 1,008 kg, 880 kg and 1,143 kg. Powell’s 10-K names the raw materials a switchgear builder buys as “steel, copper and aluminum, as well as various engineered electrical components,” which is the whole 232 exposure in one sentence: the metal is dutied on the way in, the engineered components are dutied by origin.
The Copper Tariff Alone
Take the copper on its own. At the IMF global copper price of $9,995 per tonne for September 2025 (FRED PCOPPUSDM), the copper content of the UPS is worth about $3,600, the lineup’s $10,100, the genset’s $8,800 and the Megapack’s $11,400. If every kilogram enters as imported semi-finished copper, the 50% duty is $1,800, $5,000, $4,400 and $5,700 respectively. On the Megapack that is 0.41% of the $1.39 million unit price.
Source: Open Factory Tariff Exposure Calculator, IMF via FRED PCOPPUSDM, Proclamation 10962
The copper tariff a vendor names in the surcharge letter is worth $1,800 to $5,700 per unit, and a letter that quotes a percentage of contract price instead of kilograms cannot be checked against that number. The reason a larger surcharge is not simply wrong is the price channel: US copper wire and cable PPI rose 11.9% in the year to September 2025 while the IMF world copper price rose 7.9%, and aluminum mill shapes rose 25.8% against 8.0% for world aluminum (BLS PPI WPU10260314, WPU102501; FRED PCOPPUSDM, PALUMUSDM). The gap between the US mill price and the world price is the tariff showing up in the domestic price, and a US OEM pays it whether its copper is imported or not. The Copper and Wire Price Sheet carries both series monthly so a buyer can see which one a surcharge is indexed to.
Source: BLS PPI WPU1017, WPU10260314, WPU102501, WPU1175 and IMF PCOPPUSDM, PALUMUSDM via Open Factory Tariff Exposure Calculator
Steel mill products rose 12.4% and the switchgear PPI rose 11.1% over the same twelve months, so the switchgear index moved with its metal, not ahead of it. The Lead-Time Monitor carries the switchgear and transformer PPI beside the published lead times; the price series is the one input a buyer can check without an RFQ.
Declaring the Metal in Kilograms
The content basis is not a convenience for the importer, it is a filing obligation. Proclamation 10962 directs CBP to issue “authoritative guidance mandating strict compliance with declaration requirements for copper content in imported articles” and names the penalties for underreporting: “significant monetary penalties, loss of import privileges, and criminal liability.” The BIS notice of August 19 says the same thing for the 407 new derivatives: 232 duty “will apply to the steel and aluminum content” and “the non-steel and non-aluminum content will remain subject to the reciprocal and other applicable tariffs.” Two numbers therefore go on every entry line for a derivative: the kilograms of covered metal and the value of that metal, and the reciprocal layer is computed on what is left.
For a US OEM buying semis the declaration is trivial, because a copper bar is copper and the 85% content share we use in the model only strips out fabrication. For an importer of a finished 8504.23 transformer it is a 40-tonne engineering exercise: the GOES core, the tank steel and the clamping structure have to be weighed and valued separately from the copper windings, the oil and the bushings, and the mill certificates for the core steel have to be on file, because the 10% rate under 9903.81.92 for US-melted steel is only available with proof of melt. The 25% steel share we use for a substation transformer in the paid section is our estimate; the buyer’s declared share will be audited against the vendor’s drawings, not ours.
Foreign trade zones and bonded warehouses do not change any of this. Duty is assessed at the rate in force on the date of withdrawal for consumption, so a lineup parked in a zone through a rate change pays the new rate, and 232 metal duty cannot be avoided by zone status on goods that enter US commerce. What a zone does buy is time: a Megapack integrator holding Chinese cells in bond in December 2025 pays 7.5% Section 301 if it withdraws before January 1 and 25% after, a 17.5-point difference on the cell value that the Tariff Exposure Calculator prints as two dated rows. The Copper and Wire Price Sheet carries the COMEX and LME prices a declared copper value will be checked against.
Where the Duty Sits, Line by Line
Now the value BOM with origins. For the US-assembly base case we gave each input the origin a US OEM most plausibly uses in 2025: copper, steel and aluminum semis from Mexico under USMCA (which removes MFN and the IEEPA layers but not 232, since USMCA has no carve-out from the metal proclamations), IGBT modules from Japan (Annex II of EO 14257 exempts semiconductors from the reciprocal tariff), film capacitors and half the control boards from China, vacuum interrupters from the EU, engines, alternator winding, relays, inverters and assembly in the United States, and LFP cells from China.
Source: Open Factory Tariff Exposure Calculator
The largest single line is the Megapack’s cells at 9.0 points of unit value (22% of value at 40.9% duty), then the lineup’s steel enclosure at 6.0 points, the UPS’s Chinese capacitors at 4.4, the Chinese half of its control boards at 3.5, and the lineup’s copper bus at 3.4. IGBT modules, 18% of UPS value, carry zero: Free under column 1, exempt from the reciprocal, and not Chinese. The UPS’s 17.1 points split 9.2 on metal content and 7.7 on Chinese electronics, and switching the capacitors and boards to Japanese or European suppliers would cut the electronics half to about 2 points, because EU and Japanese goods pay a flat 15% inclusive of MFN under EO 14326 (90 FR 37963) rather than 55%.
The genset is the lightest case at 6.7 points because its two largest value lines, a US-built engine (42% of value) and a US-wound alternator (15%), carry duty only on the imported winding wire, and its steel and radiator lines are small. That result holds for Caterpillar and Cummins packages built in Indiana; a mtu or Rolls-Royce set imported from Germany pays the 15% inclusive rate on the whole unit. The Genset TCO tool takes either number as a landed-cost input, and the Gensets Sold Out Through 2028 piece covers why the origin choice is mostly about slots, not duty, this year.
The Same Four Products, Finished, From China
Import the finished good instead and the metal layers vanish while the origin layers take over. A Chinese UPS pays 0 MFN plus 25 (List 3) plus 20 (fentanyl, EO 14228, 90 FR 11463) plus 10 (reciprocal, EO 14334, 90 FR 39305, through November 10, 2025): 55.0%. The lineup pays 2.7 plus 25 plus 20 plus 10, or 57.7%. The genset 57.0%. The BESS 3.4 plus 7.5 plus 20 plus 10, or 40.9%, becoming 58.4% when List 4A gives way to the 25% battery rate on January 1, 2026.
Source: Open Factory Tariff Exposure Calculator
Forty-one to fifty-eight points against 7 to 17 for US assembly. Nobody buys a Chinese 15 kV ANSI lineup for a US datacenter, but plenty of buyers were quoted Chinese BESS in 2024, and the 40.9% stack is why Powin, which relied on Chinese LFP cells, filed for Chapter 11 in June 2025 with more than $300 million of debt (TechCrunch, June 12, 2025) citing “uncertainties over levels of US import tariffs” (Energy-Storage.News, June 11, 2025); its former CEO said the company had been “searching for alternative domestic suppliers, but the supply chain wasn’t sufficiently mature.” The BESS as UPS TCO uses the 58.4% figure as the 2026 base case for Chinese cells.
The Lineup, Nine Ways
The switchgear lineup is where the inversion bites hardest, because a US builder’s exposure is almost entirely metal and a Mexican builder’s is zero. Under USMCA a qualifying lineup from Monterrey or Apodaca pays no MFN (column 1 special), no fentanyl duty (EO 14232, 90 FR 11787), no reciprocal (HTS 9903.01.27), and no 232 because 8537.20.00 is not a derivative. The US-built lineup pays 4.2 points on imported copper bus, 6.0 on imported steel sheet, 0.4 on the aluminum in its CTs, and 1.7 on European interrupters: 12.7 points.
Source: Open Factory Tariff Exposure Calculator
Zero for Mexico under USMCA, 12.7 for US-built, 15.0 for the EU and Japan, 17.7 for Korea (2.7 plus the 15% Korea rate), 22.7 for Vietnam, 27.7 for a non-USMCA Mexican unit (25% fentanyl), 52.7 for India since EO 14329 (90 FR 38701) added 25 points on August 27, and 57.7 for China. Schneider, ABB and Siemens build ANSI metal-clad gear in Mexico, and on October 10, 2025 that gear enters at 0% while Eaton’s and Powell’s US-built sections carry 12.7 points of metal duty in their cost base. Whether that shows in the quote depends on how much of the 232 cost a US builder can pass through in a market where the Lead-Time Monitor has 15 kV metal-clad at 60 to 80 published weeks; the Public Bid-Tab Price Book is where the $/section awards will show it first. The second BIS inclusions window that opened September 15, 2025 (90 FR 44799) is the mechanism by which 8537.20 could join the derivative list and close the gap; until it does, a Mexican origin certificate is worth 12.7 points.
The Megapack Stack, Cells Only
The Megapack case is the mirror image: the metal is small, the cells are everything. Tesla builds US Megapacks at Lathrop, California (target 40 GWh a year), so the unit itself never crosses a border; the cells do. With cells at 22% of unit value ($78/kWh of $355/kWh, under the $94/kWh China pack average BloombergNEF reported for 2024), Chinese LFP cells at 40.9% add 9.0 points to the unit and 12.8 points from January 1, 2026. Add 3.7 points of 232 metal and Mexican cable and the Lathrop unit carries 12.6 points today and 16.5 next year.
Source: Open Factory Tariff Exposure Calculator
Nine points today, 12.8 in January, 4.0 with Korean cells (3.4 MFN plus 15% reciprocal on 22% of value), 3.3 with Japanese cells, zero with US cells. The 58.4% headline applies only to a finished Chinese BESS; a US-assembled block with Chinese cells pays it on a fifth of its value. For a buyer comparing a Megapack quote against a Chinese-integrated system, the MEP Cost Table carries BESS at $/kWh installed and the calculator carries the duty on top; the two numbers move in opposite directions after January 1.
Thirteen Instruments in Twelve Months
Every number above changed at least once between February and October 2025, and the January battery step is already scheduled. The metal proclamations came in February (25%), June (50%) and August (copper); the reciprocal order in April, its country rates in August, India’s second 25 points on August 27; the non-stacking order in April; the BIS inclusions on August 18. A PO signed in January 2025 against a 2.7% column 1 rate now sits under six layers, three of which did not exist when it was signed.
Source: Open Factory Tariff Exposure Calculator, Federal Register
Thirteen rows, eight of them effective between June 4 and August 27, 2025. The OEM Disclosure Scorecard scores whether a vendor publishes the HTS code and duty layers behind a surcharge or sends a percentage; a percentage cannot be reproduced from the schedule, a heading can. The Datacenter Electrical Roadmap carries the two dates that matter next: November 10, 2025 for the China reciprocal truce and January 1, 2026 for the battery rate.
What the Calculator Is and Is Not
The Tariff Exposure Calculator is a version 0 compilation, not a customs ruling. Its inputs are an HTS line, a country of origin, and, for a derivative, the declared metal content share; its outputs are the layers above with the Chapter 99 heading, the Federal Register citation and the date we last checked each one. Every rate in it comes from the HTSUS chapter 99 notes and the proclamations and orders cited above, and a change in any of them shows up as a new dated row, never as a silent edit. It holds 18 lines for the four products here and about 200 in total across electrical gear, machine tools and copper.
It does not determine origin. Whether a Mexican lineup with Chinese boards qualifies under USMCA is a rules-of-origin question decided by the tariff shift and regional value content tests in the agreement’s product-specific rules, and a customs broker or counsel answers it, not a calculator. It does not carry antidumping or countervailing duties, none of which apply to the four finished lines here but several of which apply to inputs such as aluminum extrusions. And it does not know your price. A duty percentage without a price is a rate, and a rate is what the surcharge letter already gave you; the Public Bid-Tab Price Book, launched in September with award prices for transformers, switchgear sections and gensets from public procurement records, is where the percentage becomes dollars per section.
What To Do Monday
Ask every open electrical quote for three things before you sign: the HTS line the vendor will declare, the country of origin of the finished good, and the metal content in kilograms the vendor will report on the entry. With those three you can reproduce the vendor’s tariff number in the Tariff Exposure Calculator in five minutes, and you will find that a US-built lineup’s exposure is about 12.7 points of metal, not the 25 or 50 the surcharge letter implies, and that a USMCA-qualifying Mexican unit’s is zero. For BESS, ask for the cell origin and the cell value share; the difference between Chinese and Korean cells is 5 points of unit price today and 9 in January. Run the quote through Quote Check against the Bid-Tab bands so the tariff line is judged against a price, not a percentage. Then write the clause: name the HTS code, the origin, the baseline stack by heading on the quote date, and who receives any refund. Most POs signed before 2025 have no such clause, which is why the refund fights of 2026 will be about contracts, not customs.
Behind the paywall: the same four products with origin switched (Mexico assembly for the UPS, lineup and genset, Korean and US cells for the Megapack, and a substation transformer sourced from Korea, India and Mexico), the landed-cost delta per product, with the 40.0-point penalty an Indian lineup carries and the 26.2-point gap between a Korean and an Indian 10 MVA transformer, plus the eight clauses of a tariff pass-through that can be audited against a CBP entry summary. All of it runs in the Tariff Exposure Calculator.