Product classification
HS code for Power transformer: 8504.23
Electrical transformers, liquid dielectric, having a power handling capacity exceeding 10,000kVA.
Classification of power transformer under HS 8504.23
HS code 8504.23 is applied to large-scale electrical transformers that utilize a liquid dielectric for insulation and cooling. Classification within heading 8504 is based on the principle of electromagnetic induction to transform alternating current from one voltage level to another. The specific subheading 8504.23 is reserved for liquid-dielectric transformers with a power handling capacity exceeding 10,000 kVA (10 MVA). These units are typically found in electrical substations, power plants, or large industrial facilities where high-voltage transmission is required. The presence of a liquid, such as mineral oil, silicone fluid, or synthetic esters, is a primary requirement for this code. The liquid serves two purposes: it provides electrical insulation between internal components and acts as a coolant to dissipate heat generated during operation. The capacity threshold of 10,000 kVA is a strict boundary defined by the Harmonized System to categorize equipment by its industrial scale. Units with lower capacities are classified under subheadings 8504.21 or 8504.22. This classification ensures that high-capacity infrastructure equipment is distinguished from smaller distribution or dry-type transformers, which have different regulatory and duty implications. The construction of these transformers usually involves a core made of laminated silicon steel and windings of copper or aluminum, all submerged in a sealed tank filled with the dielectric fluid. The classification also includes the cooling systems attached to the transformer, such as radiators and fans, provided they are imported as part of the transformer unit.
- Covers
- Large oil-filled power transformers
- Step-up transformers for power stations (>10,000 kVA)
- Main grid transmission transformers
- Industrial liquid-cooled transformers exceeding 10 MVA
- Liquid-insulated furnace transformers (>10,000 kVA)
- Also under 8504.23
- Siemens large power transformers
- ABB EHV/UHV transformers
- GE Grid Solutions power transformers
- Mitsubishi Electric large transformers
- Hyundai Electric ultra-high voltage transformers
Codes often confused with 8504.23
Common mistake. The most common misclassification occurs with HS code 8504.22, which covers liquid dielectric transformers with a capacity between 650 kVA and 10,000 kVA. Importers often fail to verify the exact kVA rating on the nameplate. Additionally, dry-type transformers (which do not use liquid) are classified under 8504.34 if they exceed 500 kVA, and should never be placed under 8504.23 regardless of their power capacity.
Top exporters and importers of HS 850423 (the code used for power transformer), 2025
In 2025, the largest exporter of HS 850423 (the code used for power transformer) in UN Comtrade data was China, with 31% of world exports; the largest importer in UN Comtrade data was the United States, with 36% of world imports. Countries that did not report 2025 data are estimated from partner records, which can understate them.
Figures cover everything classified under HS 850423, not only power transformer.
Top exporters 2025 · share of world exports
- 1 China $3.7B 31% of world exports
- 2 South Korea $1.3B 11% of world exports
- 3 Türkiye $1.1B 9.4% of world exports
World total: $12.0B Reported figures on UN Comtrade ↗
Top importers 2025 · share of world imports
- 1 United States $4.1B 36% of world imports
- 2 Saudi Arabia $910M 7.8% of world imports
- 3 Germany $435M 3.7% of world imports
World total: $11.6B Reported figures on UN Comtrade ↗
How these figures are built
109 countries reported 2025 trade to UN Comtrade in HS 2022, and their own totals are used. Countries that did not report are estimated from what other countries recorded trading with them. Those estimates miss trade with other non-reporting countries, so they can be low, and a non-reporting country can rank higher than shown or be missing from the list. World totals add both and leave out trade between two non-reporting countries. Figures are in current US dollars; reported imports are mostly valued CIF and exports FOB, and exports include re-exports. The UN Comtrade links show the underlying records; they can also list a few reporters left out here (regional groups and older HS editions).
Source: UN Comtrade (United Nations Statistics Division), 2025 annual data.
Brazil NCM code for power transformer
Brazil classifies power transformer under NCM 8504.23.00: HS 8504.23 with 00 added.
Source: Siscomex NCM table, updated Oct 2026. The Portuguese text on each NCM page is the official one.
Questions about power transformer
What is the HS code for Power transformer?
The HS code for Power transformer is 850423 (Electrical transformers; liquid dielectric, having a power handling capacity exceeding 10,000kVA). For a liquid dielectric power transformer with a capacity exceeding 10,000 kVA, the HS code is 8504.23.
How do I classify Power transformer for customs?
Power transformer is classified under HS code 850423 — Electrical transformers; liquid dielectric, having a power handling capacity exceeding 10,000kVA. This is a 6-digit subheading level code.
What defines a liquid dielectric in this classification?
A liquid dielectric refers to an insulating fluid, typically mineral oil, used within the transformer tank to prevent electrical arcing and to facilitate cooling.
Which countries are the top exporters of power transformer (HS 850423)?
In 2025, the top exporters of HS 850423 (the code used for power transformer) in UN Comtrade data were China ($3.7B, 31% of world exports), South Korea ($1.3B) and Türkiye ($1.1B). World exports came to about $12.0B, adding countries' reported figures and partner-based estimates for those that did not report (UN Comtrade data). Countries that did not report 2025 data are estimated from partner records, which can understate them.
Which countries are the top importers of power transformer (HS 850423)?
In 2025, the top importers of HS 850423 (the code used for power transformer) in UN Comtrade data were the United States ($4.1B, 36% of world imports), Saudi Arabia ($910M) and Germany ($435M). World imports came to about $11.6B, adding countries' reported figures and partner-based estimates for those that did not report (UN Comtrade data). Countries that did not report 2025 data are estimated from partner records, which can understate them.
Is the HS code for Power transformer the same in all countries?
The base HS code 850423 for Power transformer is internationally standardized for the first 6 digits across 200+ countries. Individual countries may add additional digits for national tariff lines and specific classifications.
What is the NCM code for power transformer in Brazil?
In Brazil, power transformer (HS 850423) is classified under NCM 8504.23.00.