Discover our range of cheap Type 21 radiators, the perfect compromise when you need serious heat without the full depth of a Type 22. These are double panel single convector radiators, often referred to as P+ radiators.

The design features two panels but only one set of internal fins, allowing for increased heat output in a slim double radiator profile. This makes them an ideal solution for narrower hallways, landings, or rooms where space is limited. Find your Type 21 and unbeatable value below.

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Buying Type 21 Radiators: Quick Tip

A Type 21 radiator has two panels and one set of convector fins. That combo is a popular “middle ground” — more output than Type 20 (no fins), but usually slimmer than a Type 22. If you’re trying to hit a specific BTU/Watts figure without going too bulky, Type 21 is often the sweet spot for bedrooms, kitchens and medium-sized living spaces.

Who Should Buy a Type 21 Radiator?

And who should consider alternatives

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Who Should Buy

Standard wet central heating systems

Ideal if you’ve already got a boiler and pipework in place. Type 21 radiators are a common choice for upgrades, offering a strong balance of performance and straightforward installation.

Need a stronger output in a sensible depth

The extra panel plus one finned convector layer improves heat output and circulation, making Type 21 a reliable option when a single panel radiator feels underpowered.

Medium rooms and everyday family spaces

Great for bedrooms, kitchens, dining rooms and moderate-sized lounges where you want quicker warm-up and comfortable heat, without going for the deepest radiator type.

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Who Shouldn't Buy

Large rooms with high heat loss

For big spaces, lots of glazing, or colder external walls, you may need more output than a Type 21 can provide in a practical size — a Type 22 (or a larger radiator) often makes it easier to reach the target.

Homes without central heating pipework

Type 21 radiators require a water-based system. If you don’t have a wet setup, adding pipework can be disruptive — electric radiators are usually the simpler alternative.

You’re prioritising a designer statement

Type 21 radiators are practical workhorses. If the radiator is part of your interior design, consider vertical styles, flat designer panels, or column radiators to better match the room’s look.

FAQs About Type 21 Radiators

Help with choosing, sizing and performance

  • What is a Type 21 radiator?

    A Type 21 radiator is a double panel radiator with one set of convector fins between the panels. The extra panel area plus the fins increase heat transfer and airflow, giving higher output than a Type 20 of the same size and a faster warm-up in many rooms.

  • What is the difference between Type 21 and Type 22 radiators?

    Both have two panels, but a Type 21 has one set of convector fins, while a Type 22 has two sets of fins (one per panel). Because it has more finned surface area, a Type 22 typically produces more heat than a Type 21 in the same width and height.

  • How do I choose the right size Type 21 radiator?

    Calculate your room’s required output in BTUs or Watts, factoring in room dimensions, insulation, windows and how the space is used. Then choose a Type 21 radiator that meets or slightly exceeds that figure. If wall space is limited, moving up in height or choosing a higher-output type may be the simplest way to hit your target.