Single Panel vs Double Panel Radiators: Which One is Right for You?

If you're shopping for radiators, you've probably noticed terms like "Type 11", "Type 21", and "Type 22" scattered across product listings. These aren't just industry jargon they represent fundamentally different radiator designs that can mean the difference between a warm, comfortable home and one that never quite reaches the right temperature.

In this guide, we'll cut through the confusion with real numbers, practical examples, and honest advice to help you choose the right radiator for every room in your home.

The Quick Answer: What Do the Numbers Mean?

The type number tells you exactly what's inside the radiator:

• Type 11 (Single Panel, Single Convector): One panel + one set of fins = slimmest profile, lowest output
• Type 21 (Double Panel, Single Convector): Two panels + one set of fins = medium profile, higher output
• Type 22 (Double Panel, Double Convector): Two panels + two sets of fins = deepest profile, highest output

The first digit indicates the number of panels, the second indicates the number of convector fin sets. Simple once you know it.

How Much Difference Does It Actually Make?

This is where real numbers matter. Let's compare three radiators, all 600mm high x 1000mm long:

The Type 22 delivers 74% more heat than the Type 11 in the same width and height. That's not a small difference—it could be the difference between a room that heats in 20 minutes versus one that takes an hour and still feels cold.

Understanding BTU Requirements: The Foundation of Good Radiator Selection

Before choosing between single and double panels, you need to know how much heat your room actually requires. This is measured in BTU (British Thermal Units) or Watts. Use our BTU Calculator to get an accurate figure for your specific room.

Typical BTU Requirements by Room Type

These figures assume standard 2.4m ceiling height, double-glazed windows, and moderate UK insulation:

These are starting points. You'll need more BTU if your room has:

• Single glazing (add 20-25%)
• External walls on multiple sides (add 10-15% per additional wall)
• High ceilings over 2.7m (add proportionally)
• Poor insulation or solid walls
• North-facing aspect

Real Example: Choosing a Bedroom Radiator

Let's say you have a 4m x 3.5m bedroom with one external wall and double glazing. A BTU calculator suggests you need approximately 3,500 BTU.

Your options:

• Type 11 radiator, 600mm x 1400mm = 2,801 BTU ❌ Too small
• Type 21 radiator, 600mm x 1000mm = 3,792 BTU ✓ Good fit
• Type 22 radiator, 600mm x 800mm = 3,900 BTU ✓ Good fit, more compact

Notice how the Type 22 achieves similar output in a smaller footprint. This matters when wall space is limited.

When to Choose a Single Panel Radiator (Type 11)

Single panel radiators aren't inferior, they're designed for specific situations:

Ideal for:

• Small bathrooms and WCs where you might only need 1,500-2,000 BTU
• Well-insulated new builds that retain heat efficiently
• Utility rooms and boot rooms that don't need to be particularly warm
• Hallways and landings where radiators must fit tight spaces
• Secondary heating in rooms with other heat sources

Practical benefits:

• Projects only 46-50mm from the wall
• Lighter weight, easier to install
• Lower purchase price (typically 25-35% less than equivalent Type 22)
• Heats up faster due to lower water volume
• Less visually intrusive

The honest drawback:
If you undersize your heating, you'll end up with a radiator running constantly at maximum, struggling to maintain temperature. This uses more energy than a correctly-sized Type 21 or Type 22 cycling on and off as needed.

When to Choose a Double Panel Radiator (Type 21 or Type 22)

Type 21: The Middle Ground

Type 21 radiators offer a compelling compromise, significantly more output than Type 11, without the bulk of Type 22.

Best suited for:

• Medium bedrooms (3m x 4m to 4m x 4m)
• Dining rooms
• Home offices
• Rooms where you want higher output but limited wall depth

At around 64mm projection, Type 21 radiators are noticeably slimmer than Type 22 (100mm+). One forum user reported swapping a Type 22 for Type 21 specifically because the deeper radiator protruded awkwardly in their hallway.

Type 22: Maximum Heat Output

When you need serious heating power, Type 22 is the standard choice.

Best suited for:

• Large living rooms and lounges
• Open-plan spaces
• Rooms with high ceilings
• Older properties with solid walls and poor insulation
• Conservatories and extensions
• Any room where you'd otherwise need two smaller radiators

Heat Output Comparison for Popular Sizes (at ΔT50)

The Delta T Factor: Why Heat Pump Owners Need Bigger Radiators

This section is crucial if you're considering a heat pump now or in the future. For a deeper understanding, read our complete guide to Delta T Ratings: T50, T60, T70 Explained.

What is Delta T?

Delta T (ΔT) measures the temperature difference between your radiator's average water temperature and your room temperature. The UK standard is ΔT50, which assumes:

• Flow temperature: 75°C
• Return temperature: 65°C
• Room temperature: 20°C

All the BTU figures quoted above are at ΔT50, the legal standard for radiator advertising in the UK.

Why Heat Pumps Change Everything

Heat pumps operate most efficiently at much lower water temperatures (35-50°C versus 65-75°C for gas boilers). This means they work at approximately ΔT30, which dramatically reduces radiator output.

The conversion is significant:
To convert ΔT50 output to ΔT30, multiply by 0.51

So that 600 x 1000mm Type 22 radiator that outputs 1,788 W at ΔT50? With a heat pump at ΔT30, it delivers only 912 W roughly half.

Future-Proofing Your Radiator Purchase

If you might install a heat pump within the next 10-15 years, consider:

• Buying radiators based on ΔT30 output (roughly double the physical size)
• Opting for Type 22 where you might have chosen Type 11 or Type 21
• Using larger radiators now and controlling temperature with thermostatic radiator valves (TRVs)

The government is pushing heat pump adoption, and oversized radiators running at lower temperatures actually provide more comfortable, even heating with less cycling.

Designer Radiators: Style Meets Performance

If standard panel radiators don't suit your aesthetic, our designer radiator range offers the same single and double panel options in more contemporary styles.

Popular alternatives include:

• Vertical Designer Radiators – Ideal when horizontal wall space is limited but you need high heat output. Available in single and double configurations.
• Horizontal Designer Radiators – Modern flat-panel designs that blend seamlessly with contemporary interiors.
• Column Radiators – Traditional style with excellent heat output. Available in 2, 3, and 4 column options for varying BTU requirements.
• Aluminium Radiators – Lightweight and quick to heat up, perfect for homes that aren't occupied all day.

Bathroom Heating: Towel Rails vs Panel Radiators

For bathrooms, you have additional options beyond standard panel radiators. Our heated towel rails serve dual purposes—warming the room whilst keeping your towels toasty.

Consider these options:

• Chrome Towel Rails – Classic bathroom aesthetic with excellent heat output
• Black Towel Rails – Contemporary look for modern bathrooms
• White Towel Rails – Clean, minimal design
• Anthracite Towel Rails – On-trend grey finish

For bathrooms without central heating access, our electric towel rails provide independent heating—perfect for summer use when your boiler is off.

Pro tip: For larger bathrooms (over 6m²), a standard towel rail may not provide sufficient heat alone. Consider supplementing with a compact panel radiator or choosing a dual fuel towel rail with a higher BTU output.

Installation and Replacement Considerations

Can I Replace a Single with a Double?

Yes, but consider:

1. Bracket strength: Double panel radiators are significantly heavier. A 600 x 1200mm Type 22 weighs approximately 38.6kg versus 20.1kg for Type 11. You'll likely need new, stronger brackets.
2. Wall depth: Type 22 projects about 100mm from the wall versus 46mm for Type 11. Check this won't block doorways, create awkward corners, or look disproportionate.
3. Pipework: Pipe centres might differ. A plumber can adjust this, but it adds to installation cost.
4. Boiler capacity: Adding higher-output radiators increases demand on your boiler. If you're upgrading multiple radiators, check your boiler can handle the additional load.

Valve Positioning Matters

For optimal heat output matching the ΔT rating, install:

• Flow valve at the top of the radiator
• Return valve at the bottom, on the opposite side

This ensures hot water circulates properly through the entire radiator rather than short-circuiting. Browse our range of radiator valves for quality options in various finishes.

Cost Comparison: Is Double Panel Worth the Extra Money?

Typical price difference (based on mid-range brands):

The Type 22 costs roughly 50-60% more than Type 11, but delivers 74% more heat. On a cost-per-BTU basis, double panel radiators often represent better value for larger rooms.

Running costs:
There's a common misconception that bigger radiators cost more to run. In reality:

• A correctly-sized radiator reaches temperature and cycles off
• An undersized radiator runs continuously, struggling to maintain temperature
• The correctly-sized option typically uses less energy overall

Room-by-Room Recommendations

Bathrooms

• Small en-suite (under 4m²): Type 11 radiator or heated towel rail
• Family bathroom (4-8m²): Type 21 or consider a dual-fuel towel radiator for summer use

Bedrooms

• Single/guest bedroom: Type 11 or Type 21 depending on room size and insulation
• Master bedroom: Type 21 or Type 22, especially if you prefer warmer sleeping conditions

Living Spaces

• Living room under 15m²: Type 21 often sufficient in well-insulated homes
• Living room over 15m²: Type 22 recommended
• Open-plan areas: Type 22, possibly multiple radiators on different walls

Hallways and Stairs

• Narrow hallway: Type 11 for slim profile
• Wide hallway/entrance: Type 21 provides better heat without excessive depth

Common Mistakes to Avoid

1. Buying on size alone: A 600 x 1000mm radiator could be Type 11, 21, or 22 with vastly different outputs. Always check BTU/Watt ratings.
2. Ignoring ΔT ratings: Some retailers quote outputs at ΔT60 or ΔT70, making radiators appear more powerful than they are at the UK standard ΔT50. Always compare at ΔT50. Learn more in our Delta T guide.
3. Undersizing to save money: A radiator that's too small will never properly heat your room and may actually cost more to run.
4. Forgetting about future heating systems: If heat pumps are in your future, size radiators for ΔT30 now.
5. Not accounting for room specifics: Two rooms of identical size can have very different heating requirements based on insulation, glazing, and aspect.

Making Your Decision: A Simple Framework

1. Calculate your BTU requirement using our BTU Calculator or the estimates above
2. Add 10-15% safety margin (you can always turn a radiator down, but you can't make it produce more heat)
3. Choose the type that delivers the required output in dimensions that fit your space
4. Consider future-proofing if a heat pump is on your horizon
5. Don't forget aesthetics—you'll be looking at this radiator for years

Need Help Choosing?

At Elegant Radiators, we stock a comprehensive range of heating solutions including designer radiators, heated towel rails, and electric heating options all in various styles and finishes.

Use our BTU calculator to find your exact requirements, or contact our team for personalised advice. We've been in the radiator business for over 15 years and we're always happy to help you find the perfect heating solution for your home.

Quick Reference: Radiator Type Comparison

Related Articles:

• The Significance of BTU for the Perfect Radiator
• Delta T Ratings: T50, T60, T70 Explained for Radiators
• Which Is The Most Efficient Radiator?
• What are BTUs and Watts and How Are They Used?