Confused By UK Radiator Sizes and Types?

UK Radiator Sizes Explained: Why Replacing a Simple 600×600 Radiator Can Be So Confusing

Replacing a radiator should be simple.

You measure your old radiator, see that it’s 600mm high by 600mm wide, head online or into a merchant… and suddenly you’re faced with names like:

• Type 11
• K1
• Double Convector
• Compact
• P+
• Type 22
• Triple Panel Plus

Before long, what should have been a straightforward radiator replacement becomes surprisingly confusing.

At The GHS Group, we regularly help homeowners who want to replace an old hallway radiator and are unsure which radiator they actually need.

Why Radiator Names Cause So Much Confusion

The problem is that radiator sizes are described in two different ways:

1. Physical size – for example, 600mm x 600mm
2. Radiator type – which describes how thick the radiator is and how much heat it produces

So even if two radiators are both 600mm x 600mm, they can produce completely different amounts of heat depending on the type.

The Common UK Radiator Types Explained Simply

Here’s the easiest way to understand it.

Single Panel Radiator

Also known as:

• Type 10
• P+

This is the slimmest radiator type with:

• One flat panel
• No internal fins

These are less common in modern homes because they produce lower heat output.

Single Panel Plus

Also known as:

• Type 11
• K1

This has:

• One panel
• One set of fins behind it

This gives more heat without making the radiator much bigger.

Often used in:

• Bedrooms
• Hallways
• Smaller rooms

Double Panel Radiator

Also known as:

• Type 20

This radiator has:

• Two panels
• No fins

These are now less common because newer designs give better heat output.

Double Panel Plus

Also known as:

• Type 21 or Type 22

This is the most common radiator fitted in UK homes today.

A Type 22 radiator has:

• Two panels
• Two sets of convector fins

This creates much higher heat output while still fitting neatly under windows.

If somebody says:

“Standard modern radiator”

They usually mean a Type 22.

Triple Panel Radiator

Also known as:

• Type 33

These are much thicker and designed for rooms that need a lot of heat.

They contain:

• Three panels
• Three sets of fins

Common in:

• Conservatories
• Large open-plan spaces
• Poorly insulated rooms

Why This Matters When Replacing a Hallway Radiator

Imagine your old radiator is:

• 600mm high
• 600mm wide

You buy another 600×600 radiator, assuming it will be the same…

But if your old radiator was a Type 22 and you accidentally buy a Type 11, your new radiator could produce almost half the heat output.

The hallway may suddenly feel colder even though the radiator is technically the same “size”.

This is one of the most common mistakes homeowners make when ordering radiators online.

The Easy Way to Identify Your Existing Radiator

The easiest clue is the thickness.

Approximate radiator depths:

Radiator Type	Approx Thickness
Type 10	45mm
Type 11	60mm
Type 21	75mm
Type 22	100mm
Type 33	155mm

You can also look between the gaps:

• No fins = standard panel
• Metal zig-zag fins = convector radiator

Should You Upgrade Your Radiator Type?

Sometimes upgrading makes sense.

For example:

• Replacing a Type 11 with a Type 22 can improve hallway warmth significantly
• Modern radiators are usually more efficient
• Better heat output can help your boiler warm the house faster

However, the pipework spacing and wall space still need to be suitable.

Need Help Choosing the Right Radiator?

At The GHS Group, we can help you:

• Identify your existing radiator type
• Match the heat output correctly
• Upgrade inefficient radiators
• Replace leaking or corroded radiators
• Balance and optimise your heating system

If you need advice on replacing a radiator in your home, call 01329 285993.