How to Size Your Immersion Heater for Maximum Efficiency
Choosing the right size immersion heater is essential for ensuring energy efficiency, system longevity, and reliable hot water delivery—whether you're managing a domestic setup or an industrial tank. This guide walks you through the key considerations, calculations, and common pitfalls to help you make an informed decision.
What Is an Immersion Heater?
An immersion heater is an electric heating element submerged in a liquid—typically water—to heat it directly. These heaters are widely used in both domestic and industrial settings due to their simplicity, reliability, and compatibility with renewable energy systems
Types of Immersion Heaters:
- Copper: Ideal for soft water areas.
- Incoloy or Stainless Steel: Suitable for hard water or mildly corrosive environments.
- Titanium: Highly resistant to corrosion, perfect for industrial or aggressive liquids
Key Components:
- Heating element
- Thermostat with safety cut-off
- Tank or cylinder
Immersion Heater Installation Guide
Why Proper Sizing of an Immersion Heater Is Crucial
Correct sizing ensures:
- Energy Efficiency: Avoids overuse and unnecessary energy consumption.
- System Protection: Prevents overheating and premature failure.
- Performance: Ensures water heats quickly and consistently.
Oversized heaters may cycle inefficiently, while undersized units struggle to meet demand. Both scenarios lead to higher costs and wear
Factors to Consider When Sizing Your Immersion Heater
- Liquid Volume: Measured in litres.
- Temperature Rise: Difference between incoming water temperature and desired output (e.g., from 10°C to 60°C).
- Usage Frequency: How often the tank is emptied and refilled.
- Heat Loss: Influenced by insulation quality and ambient temperature.
- Material Compatibility: Choose the right sheath material for the liquid being heated.
Heating Element Selection Guide
How to Calculate the Size of Your Water Immersion Heater
Use this formula:
Wattage = (Volume in litres × Temperature rise in °C × 4.178) ÷ Time (in seconds)
Example:
To heat 150 litres of water from 10°C to 60°C in 2 hours:
- Temperature rise = 50°C
- Time = 2 hours = 7200 seconds
Wattage = (150 × 50 × 4.18) ÷ 7200 = ~4.36146 kW
For faster heating or larger tanks, scale accordingly. Heatrod also offers an immersion heater calculator for quick estimates.
Different Types of Immersion Heaters and Their Sizing Requirements
Application-Specific Considerations:
- Domestic Cylinders: Typically 3kW heaters.
- Industrial Tanks: May require 6kW–12kW or more, depending on volume and material
- Industrial tanks also may require even more heating and you can contact us for a bespoke solution
How to Choose the Right Immersion Heater for Your Home or Business
Key Considerations:
- Power Supply: Single or three-phase.
- Mounting Position: Side or top entry.
- Maintenance Access: Ensure space for servicing.
- Regulations: Follow UK electrical and safety standards.
Use Heatrod’s product comparison tools to match your needs with the right model.
Common Mistakes to Avoid When Sizing Your Immersion Heater
- Underestimating Wattage: Leads to slow heating and inefficiency.
- Oversizing: Wastes energy and increases wear.
- Ignoring Recovery Time: Especially important in high-demand settings.
- Neglecting Voltage Compatibility: Always match heater specs to your supply.