Type 21 Radiators, Double Panel Single Convector Radiators

Q: What is the Difference Between Type 21 and 22 Radiators?

There are many different terms used when describing radiators, so here are some of the common ones to help you tell the difference between them. As mentioned above, Type 21 radiators are also known as p+, but here are some of the others you may find: Type 10 (P1) – radiator with 1 panel and no convection fins. Type 11 (K1) – radiator with 1 panel and 1 set of convection fins. Type 22 (K2) – radiator with 2 panels and 2 sets of convection fins. Type 33 (K3) – radiator with 3 panels and 3 sets of convection fins. The type you choose will depend on the heating performance you require for a room, so we can help you decide if you aren’t sure, with our heat loss BTU calculator a simple tool to assist you.

Q: How Do I Clean a Type 21 Radiator?

It’s important to clean your Type 21 Radiator, not only for appearance, but to keep your energy bills down. This is because dust caught between the convector fins of a Type 21 radiator can trap heat and force the radiator to work harder. Before cleaning the radiator, turn off your central heating as this will stop the convection process from drawing more dust into the radiator as you clean. You can use your vacuum cleaner to remove most of the dust, then place an old towel under the radiator before using either a radiator brush or a homemade cleaning stick to push out the remaining dust from between the convector fins. You can also use a hair dryer to blow the dust down onto the towel if you prefer. To clean, simply use mild soapy water and a cloth to wipe over the front panel. Be sure to dry it thoroughly after and that’s it – one clean and ready-to-use radiator.

Q: What is the difference between a type 21 and a type 11 radiator?

A type 11 radiator, also known as a K1 radiator , is a single panel radiator with 1 set of convection fins. This is one less panel than that of a radiator type 21, so will not provide as much heat output. If you are deciding between a type 11 and type 21 radiator, this will depend on the room. Having a double panel single convector radiator will provide better heat for a slightly larger room when compared to a type 11 design, a better option for smaller rooms and spaces where the lower output is much more efficient. Use our BTU calculator to help you determine whether our type 11 or type 21 radiators are the best option for you.

Latest Advice & News

14/05/2026

Wet Room Radiators: How to Choose the Right Radiator for Moist Environments

14/05/2026

Do Radiator Covers Block Heat? What You Actually Need to Know

30/04/2026

What Your Radiator’s Colour Change Could Be Telling You

30/04/2026

Diagnosing Circulation Problems in Central Heating

Radiators Standard Premium Column Designer Towel Electric Vertical Accessories

Sort

Showing all 14 results

Filters

What is a Type 21 Radiator?

Type 21 radiators are one of the most popular radiators in homes across the country. Also known as the P+ radiator, this type of convector radiator is a familiar sight because it’s an affordable, reliable way to heat your home. Here at Stelrad, we offer an exceptional range of T21 radiators in all sizes so you can find the best fit for each room.

A type 21 radiator is a double panel single convector radiator that has a front panel, a back panel, and a single row of convector fins in between. The convection fins are the metal zig-zag structure that you will see between the front and rear panels, and as the hot water heats the panels, the convection fins heat up too. The fins add to the heated surface area, creating more heat while also helping distribute this more evenly into your room, helping you create a cosy environment in no time.

Other radiator Type 21 features to look out for are whether or not it has a top grille and if it is made from steel or another material. All of our Type 21 radiators at Stelrad are produced using stainless steel for added strength, excellent heat conductivity and, of course, rust-free longevity. We make radiators that last whether you want a standard radiator or one of our innovative electric radiators, ensuring you have long-term heating performance.

Modern radiator promotional content image

Modern radiator marketing content image 2

Designer Radiators

The Difference Between Type 21 and Type 22 Radiators

Where a Type 21 radiator is a double panel single convector radiator with a front and rear panel and one row of convector fins, Type 22 radiators are similar in that they have double panels, but they have two rows of convector fins in between. Why? Well, this means that they have an increased surface area when compared to T21 radiators.

Two rows of convector fins help to produce more heat, which is beneficial for larger rooms. However, this extra row of fins also means that the Type 22 is thicker than a Type 21 radiator, so will protrude further from the wall. If you are short on space, or simply prefer a more streamlined appearance, a Type 21 radiator will be the better choice for you.

Modern radiator marketing content image 1

The Choice Is Yours

Choosing Your Type 21 Radiator

When choosing the right radiator for your home, understanding the difference between Type 21 radiators and Type 22 is crucial. Type 21 radiators are a cost-effective and space-saving option whilst Type 22 can provide enhanced heat output and efficiency. You’ll need to consider the size of the room and its features to help you decide if T21 radiators are the perfect fit. You can use our BTU calculator to easily work out the heat output you require and assist your decision.

The room layout will also impact whether to choose a radiator Type 21 or Type 22. If placed under a window, a full-width Type 22 will provide too much heat whilst a shorter one would look odd here. A full-width Type 21 radiator on the other hand may be perfect for the job. It’s best to measure the space and consider existing furniture and units in the room that could impact performance. With these details entered into our BTU calculator, all you then have to decide on is the style and colour that best matches your décor. The good news is that we have plenty of Type 21 designer radiators to consider and help you add some style to your room alongside perfect heat performance.

Have any questions about double panel single convector radiators or need more information about Tr1 radiators? We’re here to help, so please contact us or browse our FAQs.

OUR REVIEWS

What Our Customers Say

From The Blog

TYPE 21 RADIATORS FAQS

What is the Difference Between Type 21 and 22 Radiators?

How Do I Clean a Type 21 Radiator?

What is the difference between a type 21 and a type 11 radiator?

The UK’s #1 radiator specialists since 1936, we offer the widest range of high-performance radiators for homes and businesses nationwide. Trust Stelrad to keep you warm in every room.

Your Basket

You are £350.00 away from free shipping

No products in the basket.

Sub Total £0.00

VAT included and shipping calculated at checkout.

CHECKOUT