A Guide to The Best Radiators for Heat Output

When it comes to investing in new radiators, most people will have heat output as their priority. However, aesthetics is also important to lots of our customers, and therefore we cater for both. At Stelrad, we have a huge range of radiator sizes, styles, colours, and different models with a range of heat outputs. Whether you’re looking to keep a small, medium, or large room warm, we have the idedoubleal radiator for you. Follow this guide to find the best radiators for heat output.

Should I Go for Type 22 or Type 21 Radiators for Maximum Heat Output?

If you are shopping for the best radiators for heat output, you should go for a radiator with more than one fin, but this will also depend on the size of the room you have. Some smaller rooms will heat up quickly with a one fin radiator. We have a range of different radiators at Stelrad, and the most popular are type 21 and type 22. Here are the types of radiators we have on offer at Stelrad:


  • 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.

The bigger radiators often emit lots of heat, but it will depend on one factor – how many panels and fins they have inside. You can find both single radiator and double radiator options at Stelrad, and you will need to choose between the two. Some customers buy a combination of different types of radiators for different as of course not every room in your home will be the same size. The main difference between double and single radiators is the number of fins and panels they have, reflecting the heat output. Our double radiators are P+ radiators (type 21) and K2 radiators (type 22), the single are K1 radiators.

How to Work Out How Much Heat You Need for a Specific Room

Before you purchase your radiator, you will need to work out how much heat your radiator will need to emit to heat up your whole room. Most customers like to heat up their whole house and keep it toasty in the winter and cold autumn months in the UK. To calculate and work out the heating requirements for any given room, you can use our STAR system.

The Stelrad STAR (Stelrad Technical Advanced Radiator System) heat loss calculator is a straightforward way to ensure you get the right size radiators for every room within your home. The fabric heat loss and ventilation heat loss are calculated to establish output and the size required. At Stelrad, we measure heat output in Btu/hr (British Thermal Unit per hour), the standard measurement for output of any heating device. Heat output can also be measured in watts, with 1 watt equal to 3.412 Bt/hr. At Stelrad, we have a basic and advanced heat loss calculator which you can use to get a precise result for each room.

Are Horizontal or Vertical Radiators Best for Heat Output?

When it comes to choosing between vertical radiators and horizontal radiators, if you are going for the best radiators for heat output instead of design it will likely come down to size, not orientation. Vertical radiators are often ideal in smaller rooms, like bedrooms, bathrooms, and hallways, and horizontal are better in larger rooms as they are usually bulkier. Many believe heat is lost from the top of vertical radiators, but this isn’t true. It’s not the orientation that will indicate heat output, rather the size of the radiator you go for. The only reason a vertical radiator would lose more heat or not warm up as quickly as a horizontal radiator would be if it hadn’t been drained out recently.

It’s essential to bleed your radiator at least a few times a year, to get rid of any trapped air and prevent your energy bills from skyrocketing. If a radiator hasn’t been bled it will have to work harder to heat up and therefore, use much more energy. Ensure you bleed your radiator, whether it’s vertical or horizontal!

The Best Radiators for Heat Output: Materials & Colours for Heat Output

Now you know how to work out the exact amount of heating you will need for specific rooms, you might be wondering what radiator materials are best to go for. The material your radiator is made from makes a difference in how warm the room will stay, for example, black matt radiators are great insulators, they absorb heat, whereas, white radiators reflect the heat. White radiators are still a popular option, probably the most popular option as they can subtly be fitted into any room. Investing in one colour will keep it consistent throughout your home. When deciding on the right radiator for your home and shopping for the best radiators for heat output, it will be down to a few factors! Just make sure you take some of our advice into consideration when it comes to finding the best radiators for heat output.

When it comes down to specific materials, aluminium radiators usually have the highest potential BTU output possible. Steel radiators come close! This doesn’t mean all aluminium radiators emit more heat than steel radiators, it will depend on size as well.

The Best Radiators for Heat Output: Best Designs for Heat Output

You might be wondering about the best radiator designs for emitting heat, and we can confirm there are a few. All our radiators are ideal for warming up rooms within your home, but you will need to find the best size and design to fit your rooms. It isn’t always down to design but usually the size of the radiator. However, some of the best radiators models for radiating heat are the ones with the largest surface areas, usually type 22 radiators. However, it will be a combination of size, style, room size, colour, shape, and position within the room! Good luck on your hunt for the best radiators for heat output.