Standing in front of a wall of radiators at a showroom or scrolling through endless product pages online can feel overwhelming. The numbers, the panels, the fins—it all blurs together into a confusing mess of technical jargon. But here’s the thing: choosing between Type 11, Type 21, and Type 22 radiators doesn’t have to be complicated. In fact, once you understand what those numbers actually mean and how they affect your home’s warmth, the decision becomes surprisingly straightforward.
Let’s cut through the confusion and talk about what really matters when you’re trying to heat your home efficiently without overspending on your energy bills or the radiator itself.
What Those Numbers Actually Tell You
The numbering system for radiators isn’t arbitrary—it’s a simple code that tells you exactly what you’re getting. The first number indicates how many panels the radiator has, while the second number tells you how many sets of convector fins are tucked inside. A Type 11 has one panel and one set of fins. A Type 21 bumps that up to two panels with one set of fins. And a Type 22 goes all in with two panels and two sets of fins.
Think of it like choosing between a single duvet, a duvet with a blanket, or a duvet with two blankets. Each option provides progressively more warmth, but they also take up more space and cost more money. The Convectors Radiators market offers these three main configurations because different rooms in your home have different heating needs, different amounts of wall space, and different budgets. A small downstairs toilet doesn’t need the same heating power as your sprawling living room with those beautiful but draughty bay windows.
The panels are the flat metal sections you can see from the front, while the convector fins are the zigzagged metal pieces hidden inside that help circulate warm air throughout the room. More fins mean better air circulation, which means more efficient heating. But efficiency isn’t just about pumping out maximum heat—it’s about matching the right amount of heat to your specific space.
The Slim and Simple Solution
Type 11 radiators are the minimalists of the heating world. With just one panel and one set of convector fins, they project less than sixty millimetres from your wall. This makes them perfect for narrow hallways, compact bathrooms, or any space where every centimetre counts. If you’ve ever tried to squeeze past a bulky radiator in a tight corridor, you’ll appreciate how much difference a slim profile can make to your daily life.
But slim doesn’t mean weak. A Type 11 can still generate plenty of heat for smaller rooms. The key is understanding that heat output depends on surface area and water volume. With less metal and less water inside, a Type 11 won’t produce the same British Thermal Units as its heftier cousins, but that’s often exactly what you want. Overheating a small space wastes energy and money, and it makes the room uncomfortable. Nobody wants to sleep in a bedroom that feels like a sauna.
These radiators work particularly well in modern, well-insulated homes where you don’t need aggressive heating to maintain comfort. If your property was built in the last twenty years with decent double glazing and proper wall insulation, a Type 11 might be all you need for bedrooms, home offices, and secondary bathrooms. They heat up quickly, respond well to thermostatic controls, and won’t dominate your wall space or your heating budget.
The cost savings matter too. Type 11 radiators typically cost thirty to forty percent less than equivalent Type 22 models in the same dimensions. Over a whole house, that difference adds up to real money that you could spend on better radiator valves, a smarter thermostat, or just keep in your pocket.
The Balanced Middle Ground
Type 21 radiators occupy that sweet spot between economy and power. With two panels but only one set of convector fins, they offer significantly more heat output than a Type 11 without the full depth of a Type 22. The projection from the wall sits around seventy to eighty millimetres, which is still manageable in most rooms.
This configuration makes Type 21 radiators incredibly versatile. They work beautifully in kitchens, dining rooms, and medium-sized bedrooms where you need reliable warmth but don’t have space for the bulkiest option. The extra panel means more surface area for heat to radiate from, while the single set of fins keeps the convection process efficient without adding unnecessary bulk.
One often-overlooked advantage of Type 21 radiators is their faster heat-up time compared to Type 22 models. With less water to heat inside, they reach operating temperature more quickly after your heating system kicks in. For homes where the heating runs on a timer—switching on before you wake up or before you return from work—this faster response can make a noticeable difference to comfort. You’re not sitting around in the cold waiting for your radiators to get going.
The price point reflects this middle-ground position too. You’ll typically pay fifteen to twenty-five percent more than a Type 11, but still save ten to twenty percent compared to a Type 22 in the same size. For many homeowners, this represents the best value proposition. You get substantially more heat without the premium price tag or the space compromise.
Type 21 radiators also work exceptionally well with modern condensing boilers and even with heat pump systems, provided you choose the right size. The efficiency of contemporary heating systems means you don’t always need the absolute maximum heat output—you need consistent, controllable warmth that responds to your home’s actual requirements.
The Heavy-Duty Heat Machine
Type 22 radiators are the powerhouses. Two panels, two sets of convector fins, maximum heat output. They stick out from the wall by around one hundred to one hundred and twenty millimetres, which is substantial but manageable in larger rooms with generous wall space. If you have a big living room, a poorly insulated older property, or rooms with multiple external walls, this is where you want to be looking.
The dual convector fins create excellent air circulation, drawing cool air in from below, heating it quickly, and pushing it up and out into the room. This convection process is what makes these radiators so effective at warming larger spaces. The heat doesn’t just radiate out from the panel surface—it actively circulates throughout the room, eliminating cold spots and maintaining even temperatures.
For homes transitioning to heat pump systems, Type 22 radiators often become essential. Heat pumps operate at lower flow temperatures than traditional gas boilers—typically around forty-five to fifty degrees Celsius compared to seventy to seventy-five degrees. To compensate for this lower temperature, you need more surface area to achieve the same room temperature. A Type 22 provides that extra surface area without having to install radiators so large they take over your entire wall.
Period properties benefit enormously from Type 22 radiators as well. Victorian terraces, Edwardian semis, and post-war houses often have solid walls, single-glazed windows, and draughty floors. The heat loss in these properties can be significant, and trying to warm them with Type 11 radiators would leave you constantly cold and frustrated. A properly sized Type 22 tackles the heat loss head-on, maintaining comfortable temperatures even on the coldest winter days.
The investment is higher, certainly. Type 22 radiators cost more to buy and contain more water, which means marginally higher energy costs to heat that water. But in situations where you genuinely need that heat output, the alternatives are worse. Running your heating system longer to compensate for inadequate radiators wastes more energy than simply installing the right radiator in the first place. And the discomfort of living in a cold home isn’t something you can put a price on.
Making Your Decision Based on Real Needs
Choosing the right type comes down to honest assessment of your situation. Measure your room dimensions, calculate the volume, and consider the insulation quality. A south-facing room with modern double glazing needs less heating than a north-facing room with original Victorian sash windows. A ground-floor room with an uninsulated floor loses more heat than an upstairs bedroom with a heated room below it.
Don’t just guess or assume. Take the time to work through the calculations, or use an online BTU calculator that accounts for all the variables. Input your room size, window area, insulation levels, and desired temperature. The result will give you a target heat output in watts or BTUs, and then you can match that to the specifications of Type 11, Type 21, or Type 22 radiators in different sizes.
Sometimes you’ll find that a larger Type 11 gives you the same heat output as a smaller Type 22. In that situation, consider your wall space and your budget. If you have the wall space, the larger Type 11 might save you money. If wall space is tight, the more compact Type 22 might be the better solution despite the higher price.
Think about your heating system too. If you’re running a modern condensing boiler with good controls, you have more flexibility. If you’re planning to install a heat pump in the next few years, factor that into your decision now. Installing Type 22 radiators today means you won’t need to replace them when you switch to a heat pump, saving you money and disruption in the future.
The aesthetics matter as well, even though they’re often forgotten in purely technical discussions. A bulky Type 22 radiator might provide perfect heat output, but if it looks out of place in your carefully designed room or blocks your furniture arrangement, you’re not going to be happy with it. Sometimes accepting a slightly less powerful Type 21 and compensating with better curtains or draught-proofing creates a better overall result.
Living With Your Choice
Once installed, your radiator will be working in your home for ten, fifteen, or even twenty years. That’s a long time to live with a decision, so it’s worth getting it right. A Type 11 that leaves you perpetually cold is miserable. A Type 22 that protrudes awkwardly and dominates the room becomes a constant annoyance. The right choice sits in the background, doing its job quietly and efficiently without demanding attention.
Maintenance requirements are essentially identical across all three types. You’ll need to bleed them annually to release trapped air, and you should check for leaks around the valves periodically. The fins inside Type 21 and Type 22 radiators don’t need any special attention—they’re sealed inside and just get on with their job.
Energy efficiency over the lifetime of the radiator depends more on your heating controls than on which type you choose. A Type 22 with a good thermostatic radiator valve that responds to room temperature will use energy more efficiently than a Type 11 running at full blast all the time because it can’t keep up with heat loss. Invest in decent valves and smart controls alongside your radiator choice, and you’ll see the benefits in lower bills and better comfort.
The Final Word
There’s no universally “best” type of radiator. Type 11 works brilliantly in some situations, Type 21 in others, and Type 22 in still others. The skill lies in matching the right type to your specific room, your specific property, and your specific needs. Take the time to understand what you’re actually trying to achieve, do the calculations properly, and make an informed decision based on real data rather than guesswork.
Your home deserves heating that works properly. You deserve to be warm in winter without paying through the nose for wasted energy. Whether that means slim Type 11 radiators throughout, powerful Type 22 units in your main living spaces, or a mixture of all three types depending on each room’s requirements, the right choice is the one that keeps you comfortable, fits your space, and works within your budget. Understanding the differences between these three types puts you in control of that decision, and that’s where you should be.
