Different Types of Radiators

A radiator should be chosen for the room first and the style second. That sounds obvious, but it is where many poor radiator choices begin. A radiator can look perfect on the wall and still leave the room slow to warm if the heat output is wrong, the Delta T rating is misunderstood, or the airflow is blocked by furniture, curtains or a cover.

The right radiator depends on the room’s heat loss, the heating system temperature, available wall space, pipe positions, material, controls and how the room is used. A bedroom, bathroom, hallway and open-plan living space may all need different decisions, even in the same house.

This guide explains the main radiator types in the UK, how to compare BTU and watt outputs properly, what Type 11, Type 21 and Type 22 mean, and how to choose radiators that work with boilers, heat pumps and real room layouts.

Key Takeaways

• Start with heat output in watts or BTU. Style should come after the room’s heating requirement.
• Check the Delta T rating before comparing radiators. A radiator rated at Delta T50 will produce much less heat at lower water temperatures.
• Type 22 panel radiators usually give more heat than Type 11 or Type 21 radiators of the same height and width.
• Vertical and designer radiators can work well, but they must still be sized properly.
• Heat pump systems often need larger radiators or more emitter surface area because they run at lower flow temperatures.
• Radiator covers, sofas, curtains and poor valve placement can all reduce useful heat output.
• Bathrooms, bedrooms, hallways and living rooms each have different radiator priorities.

Start With Heat Output, Not Style

The first question is not “which radiator looks best?” It is “how much heat does this room need?” Radiator output is normally shown in watts or BTU per hour. Larger rooms, poorly insulated rooms, rooms with big windows and north-facing spaces usually need more heat output than small, sheltered or well-insulated rooms.

Replacing like for like is not always reliable. The old radiator may have been undersized for years, the room may have changed, or the heating system may now run at lower temperatures. If you are moving to a heat pump, turning down boiler flow temperature, adding insulation or changing the room layout, the old radiator size may no longer be the right guide.

Use a room-by-room heat loss calculation where possible. A basic online BTU calculator can help with a first estimate, but a proper heating design is better for whole-home upgrades, heat pumps and renovations.

BTU, Watts and Delta T Explained

BTU and watts both describe heat output. In radiator shopping, BTU usually means BTU per hour, which is the amount of heat the radiator can emit over time. Watts are often easier to compare with heating calculations because many modern heat-loss reports use watts.

The conversion is simple enough: 1 watt is about 3.412 BTU per hour. A 1,000W radiator is roughly 3,412 BTU per hour. The number only matters if it is based on the right water temperature.

This is where Delta T matters. Delta T is the difference between the average water temperature inside the radiator and the target room temperature. A radiator listed at Delta T50 assumes a bigger temperature difference than one listed at Delta T30. Because hotter water gives more output, the same radiator can look much more powerful on paper if the rating uses a higher Delta T.

For a typical boiler system, Delta T50 figures are common. For heat pumps and low-temperature systems, Delta T30 or similar figures may be more relevant. Competitor buying guides increasingly stress this because comparing the wrong rating can lead to buying a radiator that will not heat the room properly.

Quick Radiator Type Comparison

Panel Radiators

Panel radiators are the standard choice in many UK homes. They are good value, widely available and easy to size because manufacturers publish outputs across many heights and widths. Most are made from steel and connect to a wet central heating system.

The type number tells you how many panels and convector fins the radiator has. A Type 11 radiator has one panel and one set of convector fins. A Type 21 has two panels and one set of fins. A Type 22 has two panels and two sets of fins. A Type 33 has three panels and three sets of fins.

More panels and fins usually mean more heat from the same wall width, but also more depth from the wall. A Type 22 radiator can be a strong choice for a living room or cold bedroom where wall space is limited. A Type 11 may be enough for a small bedroom, hallway or well-insulated room where a slimmer profile matters.

Common Panel Radiator Types

Column, Cast Iron and Traditional Radiators

Column radiators are popular in period homes because they look more traditional than flat panel radiators. They are usually made from steel or cast iron and built from repeated vertical sections. More columns and more sections generally mean more surface area and more output.

Cast iron radiators have high thermal mass. They take longer to heat up, but they also cool down slowly. That can feel pleasant in older homes where steady background warmth is valued, but it is less responsive than a modern steel panel radiator.

Do not assume a traditional radiator is automatically powerful. A narrow column radiator may look substantial but still have less output than a wider Type 22 panel radiator. Always compare the stated watt or BTU output at the correct Delta T.

Vertical and Designer Radiators

Vertical radiators are useful when wall width is limited. Kitchens, hallways, bathrooms and rooms with large windows often benefit from using height rather than width. Designer radiators can also help when the radiator is a visible part of the room.

The risk is choosing by shape alone. Tall does not always mean high output. Some vertical designer radiators have less surface area or fewer convectors than a conventional panel radiator, so they may need to be wider, deeper or paired with another emitter.

Think about heat distribution too. A very tall, narrow radiator concentrates warmth in one part of the room. That may be fine in a hallway, but an open-plan living space may feel better with two radiators or a wider emitter.

Aluminium, Steel and Cast Iron Materials

Steel is the most common radiator material. It is affordable, strong and available in a huge range of panel and designer formats. For many homes, steel is the sensible default.

Aluminium heats up quickly and cools down quickly. This responsiveness can suit rooms where heat demand changes through the day, and it can pair well with well-controlled systems. Aluminium is also lightweight, which can help on some walls, but it often costs more than steel.

Cast iron is heavy, traditional and slow to respond. It can suit period properties and rooms where a slower, steadier heat feel is desirable. It needs appropriate wall or floor support and careful handling during installation.

Material choice should not override output, water quality or installation practicalities. Wall strength, brackets, pipe centres, valves and corrosion protection all affect the final result.

Towel Rails, Electric Radiators and Specialist Emitters

Towel rails are often chosen for bathrooms, but many are better at warming towels than heating the whole room. Once covered with towels, their room heat output can fall. If the bathroom is cold, check the space-heating requirement as well as the towel-drying function.

Electric radiators are separate from wet central heating. They are useful where pipework is impractical, such as a garden room, loft conversion or occasional-use space. They are simple to install but can be expensive for daily whole-room heating if electricity is bought at standard rates.

Fan convectors and low-temperature radiators can help where wall space is tight or a heat pump system needs more output from compact emitters. They can be useful, but they bring extra considerations such as fan noise, power supply and maintenance.

Choosing Radiators by Room

Different rooms need different radiator decisions. A living room usually needs steady comfort over long periods, so output, placement and furniture clearance matter. If the radiator sits behind a sofa, much of the useful heat is wasted.

Bedrooms often need quieter, lower, steadier heat. A thermostatic radiator valve is useful, but it must sense the room temperature rather than trapped heat behind curtains. A large radiator on a lower temperature can feel more comfortable than a small radiator running very hot.

Bathrooms need towel drying, moisture resistance and safe placement. A towel rail alone may be enough in a small, well-insulated bathroom, but larger or colder bathrooms often need more output than a decorative rail provides.

Hallways are easy to underestimate. They can lose heat through doors, stairs and draughts, but wall space is often awkward. Choose robust radiators that do not create a narrow pinch point or get knocked by furniture, prams or luggage.

Kitchens and open-plan spaces often have limited wall area because of units, doors and glazing. Vertical radiators, plinth heaters, fan convectors or underfloor heating may be considered, but only after the heat output is calculated.

Radiators for Heat Pumps and Low-Temperature Systems

Heat pumps normally work best when they can supply lower-temperature water for longer periods. That changes radiator choice. A radiator that heats a room well with a gas boiler at higher temperatures may not deliver enough output at a lower heat pump flow temperature.

This does not mean every home needs huge radiators everywhere. Some rooms may already have enough output, especially if insulation has been improved. Others may need a larger panel radiator, a Type 22 or Type 33 upgrade, an extra emitter, or underfloor heating.

If you are planning a heat pump, ask for radiator outputs at the proposed design temperature. Delta T30 figures are often more relevant than Delta T50 figures. This is also where our radiator sizing guide becomes useful, because guessing can lead to either cold rooms or a heat pump running hotter than necessary.

Placement, Valves, Covers and Airflow

Radiator placement affects comfort. Under-window placement is traditional because it helps counter cold downdraughts, but modern glazing and insulation give more flexibility. What matters is that warm air can circulate and the radiator is not hidden behind furniture.

Thermostatic radiator valves can improve control, but they need to sense the room properly. A TRV tucked behind curtains, inside a radiator cover or next to a draught may behave badly. Manual valves may be acceptable in some areas, but bedrooms and living spaces usually benefit from better room control.

Radiator covers can reduce heat output if they block convection or trap warm air. If you need one for safety or appearance, choose a design with generous lower and upper ventilation and enough clearance around the radiator. Our radiator cover guide explains the trade-offs in more detail.

Common Radiator Buying Mistakes

• Choosing by appearance before checking heat output.
• Comparing BTU figures without checking the Delta T rating.
• Replacing like for like when the old radiator was already undersized.
• Assuming vertical radiators are always powerful because they are tall.
• Using a towel rail as the only bathroom heat source without checking output.
• Blocking radiators with sofas, long curtains or decorative covers.
• Ignoring valves, brackets, pipe centres and maintenance access.
• Forgetting water quality, inhibitor and corrosion protection in wet systems.

The common thread is simple: the radiator is part of a heating system, not just a wall accessory. It has to fit the room, the water temperature, the controls and the way people use the space.

Case Study: Choosing Radiators During a Renovation

Background

A family renovating a Victorian terrace wanted traditional column radiators downstairs, vertical radiators in two bedrooms and a compact panel radiator in the hallway. The first choices were based mainly on appearance and available wall space.

Assessment

A room-by-room heat output check changed the plan. The living room could still use column radiators, but the selected models needed more sections than originally expected. One bedroom did not have enough wall width for the chosen vertical radiator to meet the heat loss at the intended flow temperature.

Decision

The family kept the column radiator style downstairs, changed one bedroom to a wider double-panel radiator and moved the hallway radiator away from the door swing. They also chose TRVs that could sense room temperature properly rather than being trapped behind curtains.

Result

The final scheme still looked consistent, but it was led by heat output first and style second. The lesson is not that designer or traditional radiators are a bad idea. It is that every radiator has to earn its place by heating the room it is fitted in.

Expert Insights From Our Heating Engineers

One of our senior heating engineers with over 18 years of experience says the biggest radiator mistake is trusting the size by eye.

“Two radiators can look similar on the wall and deliver very different outputs. Panel depth, convector fins, water temperature and Delta T all matter. If you are planning a heat pump, the output at lower temperatures is the figure I care about most.”

He also stresses placement. “A good radiator in a bad position can still disappoint. Sofas, covers, curtains and poorly placed TRVs can all make a correctly sized radiator feel worse than it should.”

Frequently Asked Questions

Summing Up

The best radiator is not the most stylish one or the largest one. It is the radiator that delivers the required heat output for the room at the temperature your heating system will actually run. Once that is clear, you can choose the style, material and format that suit the space.

For most homes, panel radiators remain the practical default. Column, vertical, aluminium, cast iron, towel and electric radiators all have their place, but only when they are chosen around heat loss, Delta T, airflow and controls. Get those basics right and the radiator is far more likely to look good and heat properly.

Updated April 2026