Full comparison between dry-type and oil-immersed transformers. Learn pros, cons, cost, safety, maintenance, best applications, and which to choose in 2026.

When selecting a distribution transformer, buyers often struggle to choose between dry-type and oil-immersed models. Each design has distinct advantages in terms of safety, environment, cost, efficiency, and maintenance.

This article compares the two types in detail and helps you decide which one fits your project. We reference JGELEC’s mature product lines:

• Oil-immersed: S11-M, S13-M, S20
• Dry-type: SC(B)11, SC(B)13, SC(B)H15

Dry-Type vs Oil-Immersed Transformers – Full Comparison

1. Safety Performance

• Oil-immersed: Uses insulating oil, which is flammable. Not ideal for strict fire-safety environments.
• Dry-type: Cast resin insulation, flame-retardant, low smoke, non-toxic. Much safer indoors.

2. Installation Environment

• Oil-immersed: Best for outdoor use, substations, solar farms, industrial zones.
• Dry-type: Designed for indoors, basements, high-rises, hospitals, data centers, shopping malls.

3. Cooling System

• Oil-immersed: Natural oil circulation or forced oil cooling. Excellent heat dissipation.
• Dry-type: AN (natural air) or AF (forced air) cooling.

4. Maintenance

• Oil-immersed: Requires regular oil testing, filtration, and maintenance.
• Dry-type: Almost maintenance-free. Only periodic cleaning and inspection are needed.

5. Cost

• Oil-immersed: Lower upfront cost.
• Dry-type: Higher initial price but lower long-term maintenance cost.

6. Service Life

• Oil-immersed: 25–30 years
• Dry-type: 20–25 years

7. Energy Efficiency

Modern high-efficiency models from both types perform very well:

• S20 oil-immersed transformers have ultra-low no-load loss
• SC(B)H15 amorphous alloy dry-type transformers provide exceptional energy savings

Best Applications

Oil-Immersed Transformers (S11-M, S13-M, S20)

• Outdoor power substations
• Solar and wind power stations
• Industrial plants and manufacturing facilities
• Infrastructure and construction sites
• Mining and remote power systems

Dry-Type Transformers (SC(B)11, SC(B)13, SC(B)H15)

• Commercial buildings and high-rises
• Hospitals, schools, and airports
• Data centers and intelligent buildings
• Indoor power distribution rooms
• Urban and densely populated areas

FAQ

Q1: Can oil-immersed transformers be installed indoors?

A: They are not recommended unless equipped with a dedicated fire protection system.

Q2: Which type is more energy-efficient?

A: High-grade oil-immersed transformers (S20) have slightly better full-load efficiency, while dry-type amorphous alloy models (SCH15) excel at low-load conditions.

Q3: Which JGELEC model is best for data centers?

A: SC(B)13 or SC(B)H15 dry-type transformers are highly recommended for fire safety and stability.

Q4: Do dry-type transformers require a separate room?

A: They can be installed in general distribution rooms without additional oil containment measures.

Q5: Which transformer is better for coastal or humid areas?

A: Dry-type transformers are more resistant to moisture and corrosion.

Q6: Can JGELEC provide both types for a large project?

A: Yes, we supply complete solutions combining oil-immersed and dry-type transformers for mixed indoor and outdoor systems.

Call to Action

Choose the right transformer type based on safety, environment, budget, and maintenance capacity. JGELEC provides professional technical support to help you select the optimal solution. Contact us for datasheets, pricing, and customized designs.