HS Code 85.04 – Electric transformers, static converters (e.g. rectifiers) and inductors

HS code 8504 is a 4-digit heading in the Harmonized System that covers: Electric transformers, static converters (e.g. rectifiers) and inductors. Heading 8504 covers electric transformers, static converters (e.g., rectifiers), and inductors. This broad classification encompasses devices crucial for managing and altering electrical power across a vast spectrum of applications, from massive grid infrastructure to miniature electronic circuits. Transformers adjust voltage and current levels, vital for power transmission and distribution, as well as in audio and control systems. Static converters, such as rectifiers (AC-DC), inverters (DC-AC), and various power supplies, change the characteristics of electrical current without moving parts, making them essential for electronics, renewable energy integration, and industrial processes. Inductors, including choke coils, store energy in a magnetic field and are used for filtering, energy storage, and impedance matching. The scope is defined by the core function of converting or transforming electrical energy. This classification is paramount for trade compliance due to the diversity of products and their widespread use, impacting industries from consumer electronics to heavy industry. The heading is an integral part of Chapter 85, reflecting the fundamental electrical components necessary for virtually all electrical and electronic systems globally. Its historical significance lies in enabling the efficient distribution and utilization of electricity since the late 19th century.

Power transformers, distribution transformers, step-up transformers, step-down transformers, audio transformers, current transformers, voltage transformers, isolation transformers, switch-mode power supplies (SMPS), AC-DC rectifiers, DC-AC inverters, uninterruptible power supply (UPS) converter modules, battery chargers (rectifier components), welding rectifiers, choke coils, ferrite core inductors, air core inductors, common mode chokes, ballasts for discharge lamps, variable transformers (variacs), power adapters, solar inverters, industrial rectifiers, voltage regulators (static type), frequency converters (static type), arc welding transformers.

A common pitfall is misclassifying a complete apparatus that incorporates a transformer, converter, or inductor, rather than the component itself. For instance, a complete UPS system (which includes a battery and other features) might be classified elsewhere, while just the static converter part falls under 8504. Another error involves battery chargers which, while containing rectifiers, might be classified under other headings if they are complex units with additional functions. Generic electrical parts that are not specifically transformers, static converters, or inductors are also sometimes incorrectly placed here. Confusion can also arise with certain types of electrical control apparatus (8537) or parts of specific machines if the primary function is not the electrical conversion itself.

In 2025, the top exporters of HS code 8504 in UN Comtrade data were China ($52.6B, 30% of world exports), Germany ($13.1B) and the United States ($8.7B). World exports came to about $176.4B, 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.

In 2025, the top importers of HS code 8504 in UN Comtrade data were the United States ($35.4B, 20% of world imports), Germany ($14.0B) and China ($10.1B). World imports came to about $175.7B, 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.

HS code 8504 is a 4-digit heading under Chapter 85 of the Harmonized System. The first 2 digits (85) identify the chapter, and digits 3-4 (04) specify the heading. This code contains multiple 6-digit subheadings for precise product classification.