Type 11 vs Type 21 vs Type 22 Radiators: What's the Difference?

Choosing the right radiator is about more than just size and style. One of the most important factors affecting a radiator's heat output is its type number. If you've been comparing radiators, you've probably come across terms such as Type 11, Type 21, and Type 22.

These numbers indicate how many heating panels and convector fins are built into the radiator, which directly affects how much heat it can produce. In this guide, we'll explain the differences between each type and help you decide which is best for your room.

Understanding Radiator Type Numbers

Radiator type numbers consist of two digits:

• The first digit represents the number of water-filled panels.
• The second digit represents the number of convector fin sets.

Convector fins are metal sheets fitted between panels that increase the surface area available for heat transfer, helping the radiator warm a room more efficiently.

What is a Type 11 Radiator?

A Type 11 radiator contains:

• 1 heating panel
• 1 set of convector fins

Because it has a single panel and a single convector, a Type 11 radiator is relatively slim and lightweight. It is ideal for smaller rooms where wall space is limited and the heat demand is lower.

Advantages of Type 11 Radiators

• Compact and space-saving design
• Suitable for smaller rooms and hallways
• Lower purchase cost
• Easier to install due to lighter weight

Best For

• Bedrooms
• Home offices
• Hallways
• Small kitchens

What is a Type 21 Radiator?

A Type 21 radiator contains:

• 2 heating panels
• 1 set of convector fins

With two panels but only one convector, a Type 21 radiator offers increased heat output compared to a Type 11 while remaining slimmer than a Type 22 radiator.

Many homeowners choose Type 21 radiators when they need more heat but have limited projection from the wall.

Advantages of Type 21 Radiators

• Higher heat output than Type 11 models
• Slimmer profile than Type 22 radiators
• Good balance between size and performance
• Suitable for medium-sized rooms

Best For

• Living rooms
• Dining rooms
• Larger bedrooms
• Modern homes with limited wall depth

What is a Type 22 Radiator?

A Type 22 radiator contains:

• 2 heating panels
• 2 sets of convector fins

Type 22 radiators are among the most popular choices in UK homes because they provide excellent heat output without requiring excessive wall width. The additional convector fins significantly improve efficiency and heating performance.

Advantages of Type 22 Radiators

• High heat output
• Excellent energy efficiency
• Ideal for larger or colder rooms
• Popular choice for whole-home heating projects

Best For

• Large living rooms
• Open-plan spaces
• Extensions
• Rooms with large windows
• Poorly insulated properties

Type 11 vs Type 21 vs Type 22: Quick Comparison

Which Radiator Type Should You Choose?

The right choice depends on your room size, insulation levels, and available wall space.

• Choose Type 11 if space is limited and the room requires modest heat output.
• Choose Type 21 if you need a balance between radiator depth and heating performance.
• Choose Type 22 if maximum heat output is the priority and you have enough wall depth available.

Before purchasing any radiator, it's always recommended to calculate your room's BTU requirement to ensure you select a model capable of heating the space effectively.

Final Thoughts

Understanding radiator types makes it much easier to choose the most efficient heating solution for your home. While Type 11 radiators are perfect for smaller spaces, Type 21 models offer a practical middle ground, and Type 22 radiators deliver the highest heat output for larger or more demanding rooms.

If you're unsure which radiator is best for your property, calculating the room's BTU requirement is the best place to start. Matching the radiator type to the heating demand will help ensure your home stays comfortable while operating efficiently.