What is The Difference Between P1, K1, P+, K2 & K3 Radiators?

When it comes to selecting the best radiators for your home, you will have lots of choices if you decide to buy from Stelrad. It is not just the size of your new radiator you will need to consider, but the orientation, style, colour, and type of radiator too. Your choice will be completely up to you and your partner or family, depending on who you live with. Radiators’ primary purpose is to heat up the rooms in your home but many pick radiators for how aesthetically pleasing they look as well. If you want to make a statement in a room, as well as keep it warm, we have suitable radiators for modern and vintage homes at Stelrad. Here is our guide explaining ‘what is the difference between P1, K1, P+, K2 & K3 radiators?’, as this is something you will need to know before purchasing your new Stelrad radiators.

What Are the Different Types of Radiators?

Radiators will vary in size and will have different amounts of panels and convection fins inside depending on the type you go for. Use this simple information to distinguish the differences between all our radiator types:


  • P1 also known as Type 10, is a type of radiator with 1 radiator panel and no convection fins.
  • K1 also known as Type 11, is a type of radiator with 1 radiator panel and 1 set of convection fins.
  • P+ also known as Type 21, is a type of radiator with 2 radiator panels and 1 set of convection fins.
  • K2 also known as Type 22, is a type of radiator with 2 radiator panels and 2 sets of convection fins.
  • K3 also known as Type 33, is a type of radiator with 3 radiator panels and 3 sets of convection fins.

Make sure you also find our radiator downloads for exact details on models and types of radiators. It’s essential to bear in mind the larger the radiator, the greater the depth will be, so if you invest in K3 triple radiators they will have a much larger depth than K1 single radiators for example.

Single Panel K1 Radiators at Stelrad

Single radiators are a standard choice that will heat small and medium rooms within any home, and you will also see them referred to as type 11 radiators. Our collection of Stelrad single panel K1 radiators is affordable, yet efficient and these radiators are perfect to subtly fit behind sofas or under windows. We don’t stock P1 type 10 radiators at Stelrad, as they only have 1 panel and no convection fins, all our radiators have convection fins inside to maximise heat output.

Horizontal single radiators are a safe option that many decide to go for when investing in completely new radiators for the whole house or replacing old radiators. Single panel K1 radiators have one radiator panel and one set of convection fins, meaning they don’t have a huge heat output, but it’s enough for most rooms in the house. Single panel radiators work as bedroom radiators, hallway radiators and in any other room you see fit. Single K1 radiators are one of the easiest radiator styles to install onto the wall, depending on the size of course. Browse our selection of single radiator styles, colours, and different models today.

Double Panel K2 & P+ Radiators at Stelrad

There are two different types of double radiators we stock at Stelrad, the K2 double panel radiators range and P+ double panel radiators. The difference between them is the number of convection fins and panels they have. K2 double radiators, also known as type 22 radiators, have two panels and two sets of convection fins, whereas P+ double radiators, known as type 21 radiators, have two radiator panels and only one set of convection fins. If you want the highest heat output possible from your double radiator, you should go for a type 22 K2 radiator as more convection fins equals more heat output. A larger heat output is down to a larger surface area. Double radiators are ideal as living room radiators, or in any other spacious rooms in your home. You can search radiators by room here online to find some suggestions for each room of your home.

Triple Panel K3 Radiators at Stelrad

Triple panel radiators are also known as type 33 radiators, they have the highest output down to their large surface area that emits tons of heat. They have three radiator panels and three sets of convection fins. This type of radiator won’t look right in a small room in your home due to its depth, and you won’t likely need such a high heat output for small bedrooms and spaces within your home, such as hallways and corridors. Type 33 radiators are more appropriate for large downstairs rooms or loft conversions. Find our selection of triple K3 panel radiators to find something ideal for the larger rooms in your home. If you have a living space that is open plan and you need lots of heat to warm up the entire space, we recommend a K3 triple radiator, as they have the largest depth and consequently the greatest heat output.

Do All Types of Radiators Come in Different Styles?

Depending on the type of radiator you go for, you can find a range of different styles to suit your existing home decor. Browse our designer radiators to find both horizontal and vertical radiators to install in your home. Whether you end up picking a single, double or triple types of radiator, you will find flat front panel radiators and column radiators available, along with elegant radiators and old-fashioned radiators.

We also stock various other radiator styles to choose from at Stelrad, so have a browse. Remember you don’t always have to keep the radiators throughout your home consistent, you can change them up depending on the mood of the room. Heated towel rail radiators in vertical orientations are ideal as bathroom radiators, for example, but you probably wouldn’t fit one of these in a bedroom!

Which Radiator Type Should I Go For?

Now you know what is the difference between P1, K1, P+, K2 & K3 radiators, you will likely be ready to decide based on this information. Make sure you consider the size of your room and how much space you have for the radiator. Single radiators are ideal in smaller rooms, whereas double and triple radiators will work best in larger rooms that need more heat output from the radiator. If you have any questions regarding your radiator order or the type of radiators to buy for your home, don’t hesitate to contact us at Stelrad.