How Are Solar Panels Graded?

To distinguish the level of solar panels, you can start from the following aspects to comprehensively judge their quality and performance:

1. Cells (core components)

Grade classification:

Grade A: flawless, uniform color, neat edges, high conversion efficiency (usually ≥20%).

Grade B: slight color difference, small notches or slight scratches on the edges, slightly lower efficiency (about 1-3% lower than grade A).

Grade C: obvious color difference, fragments, hidden cracks or damage, and significantly reduced efficiency.

Technology type:

Monocrystalline silicon (Mono): high efficiency (mainly grade A), uniform black.

Polycrystalline silicon (Poly): slightly lower efficiency, with blue ice patterns on the surface.

Thin-film: flexible and light, but low efficiency, commonly seen in grade B/C.

2. Packaging materials and processes

EVA film: high-transmittance, anti-aging film for high-quality panels, no bubbles or yellowing.

Backboard: TPT (fluoroplastic) backboard is better than ordinary PET and has strong weather resistance.

Frame: Aluminum alloy frame should be flat and burr-free, with a thickness of ≥1.3mm (A-level commonly used anodizing process).

1. Conversion efficiency

A-level board: single crystal ≥20%, polycrystalline ≥17% (the highest record in the laboratory is about 26%).

The actual efficiency can be checked by the nameplate or test report. If it is more than 5% lower than the nominal value, it may be B/C level.

2. Power tolerance

A-level: nominal power error ±0~+3% (such as 300W board actual output ≥300W).

B/C level: Possible negative tolerance (such as -3%~-5%), long-term use of power decay quickly.

3. Temperature coefficient

- A-level: temperature coefficient ≤-0.35%/℃ (little performance loss at high temperature).

- Inferior board coefficient＞-0.45%/℃, efficiency drops significantly in hot areas.

4. Anti-degradation capability

Grade A: Degradation ≤1% in the first year, ≤20% in 25 years (specified in the warranty).

- Grade B/C: Degradation may reach 3-5% in the first year, no long-term warranty.

1. Surface and color

Grade A: Uniform color (single crystal pure black, polycrystalline dark blue), no spots or water marks.

Grade B/C: Obvious color difference, partial whitening or yellowing (EVA aging signs).

2. Hidden cracks and fragments

Use EL detector (or strong light flashlight oblique illumination): Grade A has no cracks; Grade B has subtle hidden cracks; Grade C has obvious cracks.

3. Frame and junction box

Grade A: No scratches on the frame, uniform sealant on the junction box, visible diode brand (such as TÜV certification).

Grade C: Thin frame (<1mm), easy to deform, rough junction box without brand.

1. International certification

Class A must: IEC 61215 (performance), IEC 61730 (safety), UL (North America), TÜV (Europe).

Class B/C may only pass partial certification or forge certificates.

2. Brand reputation

First-tier brands (such as LONGi, Jinko, First Solar) mainly promote Class A panels with a 25-year warranty.

Small factories or OEM products may mix Class B/C cells.

1. Price range

Class A: Monocrystalline silicon is about US$0.1/W (market price in 2025).

Class B: 10-30% lower in price, commonly seen in second-hand or tail goods.

Class C: 50% lower than the market price, with extremely high risk.

2. Warranty terms

Class A: 10-12 years product warranty, 25 years power guarantee (such as ≥80% in the 25th year).

B/C grade: warranty ≤ 5 years, or no official warranty.

1. Portable IV tester: measure open circuit voltage and short circuit current on site, and compare with nominal values.

2. Infrared thermal imager: local heating of inferior panels (hidden cracks or poor welding).

3. Compare power generation: under the same environment, low-level panels generate 10-20% less power per day.

1. Check certification: verify the official website of IEC/UL/TÜV certificate number.

2. Measure efficiency: use IV tester to measure whether the actual power meets the standard.

3. Look at the appearance: EL test or strong light check for hidden cracks and frame workmanship.

4. Ask about warranty: regular A-level panels provide 25 years of linear power guarantee.

The above methods can effectively distinguish the level of solar panels and avoid buying inferior products.