Amorphous alloy transformers are rated on China's GB 20052 scale from grade 1 (best) to grade 5, and the grade tracks two numbers that hit your budget: no-load loss (P₀) and load loss (Pₖ). U.S. buyers don't see those grades — they check DOE 10 CFR 431 Subpart K compliance and the loss values on the nameplate. A unit like the SCBH17 sits one grade above the SCBH15 because both losses are lower.

1. How the efficiency grades are structured

In the Chinese GB 20052 framework, amorphous distribution transformers are sorted into five efficiency grades, with grade 1 the most efficient and grade 5 the least. A higher grade means lower losses and, on paper, a smaller carbon footprint over the unit's life. [Confirm: the current GB 20052 edition and the exact grade boundaries — grade definitions shift between revisions, and this page describes the framework as the source presents it, not a specific edition.]

The U.S. doesn't use this 1–5 scale. Here, distribution transformers clear a single minimum-efficiency bar — DOE 10 CFR 431 Subpart K (§431.196 for low-voltage dry-type, §431.198 for medium-voltage dry-type) — and in the EU they meet Ecodesign Regulation 2019/1783 (PEI). So when you quote an SCBH15 or SCBH17 to a North American client, lead with the loss figures and the DOE compliance statement, not the Chinese grade. For the units that actually carry these grades, see the transformer range on the products page.

2. Grades track the two losses

An efficiency grade is shorthand for where the transformer lands on its two loss values:

• No-load loss (P₀, "iron loss") — the power the core draws around the clock just to sit energized, with no load connected. This is where amorphous wins.
• Load loss (Pₖ, "copper loss") — the loss that appears only when current flows, scaling with the square of the load.

A better grade means lower P₀ and usually lower Pₖ. Amorphous metal's near-zero magnetizing loss cuts no-load loss by roughly half to two-thirds versus a conventional grain-oriented silicon-steel core. Load loss is set more by winding design and conductor size, so it moves less between grades. We cover loss measurement and grade testing in more depth across the resources library.

3. Why the grade shows up in your operating cost

The grade isn't a badge — it's a 20- to 30-year electricity bill. Energy burned as loss is paid for every hour the transformer is connected, and no-load loss is paid even at 3 a.m. The lifetime energy draw is roughly:

E (annual kWh) = P₀ × 8760 + Pₖ × β² × 8760

where β is the load factor. At a $0.12/kWh tariff, each kilowatt of no-load loss costs about $1,050 a year before you've delivered a single amp. Run that through our loss and total-cost-of-ownership calculator to see what a one-grade step is worth on your duty cycle.

4. Grades keep climbing as the alloy and design improve

Each new amorphous grade reflects a better core alloy, tighter manufacturing, or a redesigned winding. The practical result is the same in every revision: lower P₀, and often lower Pₖ, at the same kVA. Don't read a newer grade as a different product category — it's the same dry-type amorphous transformer with a thinner energy bill. Because amorphous units shine at light load, they're a common pick for data centers and commercial buildings that run well below nameplate most of the day; our data-center calculator shows how the loss profile behaves across the load range.

5. Worked example: SCBH15 (grade 3) vs SCBH17 (grade 2)

Both are dry-type amorphous alloy cast-resin transformers. The source places the SCBH15 at grade 3 and the SCBH17 at grade 2, meaning the SCBH17 carries lower no-load and load losses and beats a conventional silicon-steel dry-type unit outright. [Confirm: the exact P₀ and Pₖ for the specific kVA and voltage you're comparing — grades are capacity-dependent, and a small SCBH15 can still out-spec a large silicon-steel unit.]

For the SCBH15 specifically, the product page lists the dry-type amorphous construction and the loss values to set against a silicon-steel unit.

6. FAQ

What do efficiency grades 1 through 5 mean?

In China's GB 20052 scale, grade 1 is the most efficient and grade 5 the least. The grade summarizes where the transformer's no-load and load losses land. The U.S. doesn't use this scale — it sets one minimum-efficiency bar under DOE 10 CFR 431 Subpart K. 

Is a higher grade always worth the upgrade cost?

Not automatically. A better grade lowers losses, but the payback depends on your load factor and electricity price. If the unit runs lightly loaded for long stretches, the no-load saving matters most; if it's heavily loaded, load loss dominates. Run both grades through the total-cost calculator before paying for the upgrade.

How do amorphous cores earn a better grade?

The amorphous metal core needs almost no magnetizing current, so no-load loss drops by roughly half to two-thirds versus a silicon-steel core. That single change is what pushes an amorphous unit into a better grade than an equivalent conventional transformer. 

Does the U.S. recognize these 1–5 grades?

No. U.S. distribution transformers must meet the DOE 10 CFR 431 Subpart K minimums (§431.196 for LV dry-type, §431.198 for MV dry-type); the EU uses Ecodesign tiers. Quote the nameplate losses and the compliance statement, not the Chinese grade, to a North American buyer.

SCBH15 vs SCBH17 — what's the actual difference?

Per the source, SCBH15 is grade 3 and SCBH17 is grade 2. The SCBH17 has lower no-load and load losses at the same rating, so it costs less to run. Both are dry-type amorphous; neither is a different technology, just a more efficient execution. 

Where do I find no-load and load loss on the nameplate?

They're listed as P₀ (no-load loss, sometimes "iron loss") and Pₖ (load loss, sometimes "copper loss"), usually at rated voltage and current. Those two numbers — not the grade — are what you model for lifecycle cost and what DOE references for compliance.

Are amorphous dry-type transformers compliant with U.S. efficiency rules?

They can be, provided the specific unit meets DOE 10 CFR 431 Subpart K for its voltage class and the applicable NEC Article 450 installation rules. Confirm the certification and the nameplate losses for the exact model; "amorphous" describes the core, not the compliance status. Use our NEC calculator to check the installation-side requirements.