Damp Heat (DH1000) Test for Solar PV Modules: Complete Guide to Moisture Resistance & Long-Term Reliability

Damp Heat (DH1000) Test - Solar PV Module Test

Solar photovoltaic (PV) modules operate outdoors for 25–30 years, often exposed to high humidity, rainfall, coastal conditions, and elevated temperatures. These environmental factors can accelerate the aging of module components such as encapsulants, backsheets, and cell interconnections.
To ensure long-term durability, modules undergo a series of reliability tests under IEC 61215 standards — and one of the most critical among them is the Damp Heat (DH1000) test.

What Is Damp Heat (DH1000) Testing in Solar PV Modules?

Damp Heat (DH1000) is an accelerated aging test defined in IEC 61215, where a solar module is exposed to:

85°C temperature
85% relative humidity
1,000 hours of continuous exposure

The aim is to simulate decades of moisture-induced degradation within a short time.

Purpose of DH1000

Assess the module’s resistance to humidity and heat
Evaluate encapsulant adhesion and stability
Test backsheet durability
Detect corrosion issues
Ensure long-term electrical insulation

Why the Damp Heat Test Is Important

Moisture is one of the biggest long-term threats to PV reliability. In real-world environments, high humidity can enter the module through micro-defects and slowly damage internal components.

DH1000 helps identify:

Moisture ingress
Corrosion of cells and contacts
Delamination tendencies
Weak encapsulant bonding
Potential-induced degradation (PID) susceptibility
Backsheet cracking

Modules passing DH1000 demonstrate strong durability in tropical, coastal, and humid regions.

DH1000 Testing Procedure: Step-by-Step

1. Test Conditions

Temperature: 85°C
Relative Humidity: 85% RH
Duration: 1,000 hours (approx. 42 days)

2. Pre-Test Measurements

Before exposure, the module undergoes:

IV curve measurement
Electroluminescence (EL) imaging
Visual inspection
Insulation resistance test

3. Environmental Chamber Exposure

The module is placed in a controlled chamber with consistent 85°C and 85% humidity for the entire duration.
No cooling cycles or temperature variations occur — the test is continuous.

4. Post-Test Evaluation

After 1,000 hours, the following are checked:

Power degradation (must be ≤5%)
Visual defects
Peel strength of encapsulation
Cell corrosion indicators
Backsheet integrity
EL imaging for microcracks

What Does DH1000 Simulate?

The DH1000 test reproduces real-world conditions such as:

1. Tropical Climate Exposure

Regions with:

High humidity
Intense heat
Frequent rains

2. Coastal Installations

High salt moisture and humidity can cause corrosion.

3. Poor Ventilation Areas

Modules installed close to walls or in high-heat zones may retain moisture.

4. Greenhouse or Agricultural Solar

High humidity environments speed up aging.

Common Failure Modes Detected in DH1000

1. Encapsulant Browning or Yellowing

EVA degradation caused by heat/humidity combination.

2. Corrosion of Metal Contacts

Moisture can corrode:

Busbars
Ribbons
Cell metallization

3. Delamination

Peeling between:

EVA and glass
EVA and cell surface
EVA and backsheet

4. Backsheet Cracking or Bubbling

Especially in cheaper or poorly formulated polymer backsheets.

5. Insulation Resistance Drop

Moisture penetration reduces safety levels.

6. Cell Microcracks

Extended humidity can weaken soldering and cause hot spots.

IEC Requirements After DH1000

For a module to pass the DH1000 test:

Power loss must remain below 5%
No major visual failures (delamination, bubbles, corrosion)
Insulation resistance must remain ≥40MΩ·m²
Safety specifications must be intact

Premium manufacturers often test beyond the standard, such as DH2000 or DH3000.

Benefits of Modules That Pass DH1000

1. Higher Reliability in Humid Environments

Critical for:

South Asia
Southeast Asia
Africa
Coastal regions

2. Lower Long-Term Degradation

Humidity-induced failures are reduced significantly.

3. Reduced O&M Costs

Less need for frequent inspections or replacements.

4. Improved System Safety

Stronger insulation and backsheet durability reduce electrical risks.

5. Better ROI for Solar Projects

Higher energy output over the module’s lifetime.

DH1000 vs Other Reliability Tests

Test	Simulates	Conditions
DH1000	Long-term heat & humidity	85°C, 85% RH, 1000 hrs
TC200	Daily thermal expansion/contraction	-40°C to +85°C
HF10	Rapid humidity freeze	85% RH to -40°C
PID Test	Voltage-driven degradation	High voltage & humidity
UV Test	Sunlight-induced aging	UV exposure for 15 kWh/m²

Together, these tests provide a complete picture of PV durability.

Applications That Benefit Most From DH1000-Certified Modules

✔️ Coastal solar farms

✔️ Tropical and humid regions

✔️ Rooftop solar in hot climates

✔️ Floating solar (high moisture exposure)

✔️ Agricultural and greenhouse solar

✔️ Off-grid humid environments

Conclusion

The Damp Heat (DH1000) test is one of the most critical reliability qualifications in the solar industry, ensuring that PV modules can withstand extreme humidity and temperature combinations over decades.
Modules passing this test deliver superior performance, lower degradation, and greater safety — making them ideal for humid, tropical, and coastal installations.

Choosing modules with strong DH test results is essential for maximizing long-term performance and securing your solar investment.

Damp Heat (DH1000) Solar PV Module – FAQ

1. What is Damp Heat (DH1000) testing in solar PV modules?

Damp Heat (DH1000) is an IEC 61215 reliability test where a solar module is exposed to 85°C temperature and 85% relative humidity for 1,000 hours to simulate long-term moisture-induced aging.

2. Why is the DH1000 test important?

The DH1000 test evaluates a module’s resistance to moisture and heat, identifying issues such as corrosion, delamination, EVA yellowing, backsheet cracking, and insulation failures.

3. How long does DH1000 testing last?

The test lasts 1,000 hours (about 42 days) under constant heat and humidity conditions.

4. What conditions are used during the DH1000 test?

The module is exposed to 85°C temperature and 85% relative humidity continuously without any cooling cycles.

5. What failures are commonly detected in DH1000 testing?

Common failures include EVA encapsulant yellowing, corrosion of metallization, delamination, backsheet cracks, moisture ingress, and reduced insulation resistance.

6. What is the maximum allowed power loss after DH1000?

IEC standards require that the power degradation stays below 5% after DH1000 testing.

7. Which installations benefit most from DH1000-tested modules?

These modules perform best in humid, tropical, coastal, floating solar, agricultural, and off-grid environments.

8. How is DH1000 different from Thermal Cycling (TC200)?

DH1000 tests heat + humidity (85°C/85% RH), while TC200 tests temperature swings from -40°C to +85°C. Both simulate different environmental stresses.

9. Do manufacturers test beyond DH1000?

Premium manufacturers may run extended tests such as DH2000 or DH3000 to prove higher durability.

10. What degradation can occur in real installations?

Modules with strong DH1000 performance usually degrade only 0.4%–0.5% annually in high-humidity environments.

Damp Heat (DH1000) Test - Solar PV Module Test