Central heating radiators come down to three checks: output, size and how the unit sits on the wall. More panels or convector surface usually give you more heat from the same footprint, while single-panel options suit tighter spaces and lighter loads. If the pipework and wall space are fixed, dimensions matter as much as output - the wrong size is the one that causes the call-back.
Center Type 21 Double Panel Single Convector Radiator - 600mm x 1200mm 5486 BTU
Type 21 steel radiator, 600x1200mm, white powder coat, 5486 BTU/h
Stelrad Softline Compact K2 Double Panel Radiator - 450mm x 900mm
Stelrad Softline Compact K2 radiator 450x900mm, white, 1.234 kW, 4212 Btu
Stelrad K3 Compact Triple Panel Radiator - 300mm x 1000mm
Stelrad K3 Compact Type 33 radiator, 300x1000mm, white
Myson Select Compact Type 33 - 500mm x 1000mm
Compact Type 33 radiator 500mm x 1000mm with 33mm pitch
Type 11 Single Radiator - 600 x 1400mm White 4455 BTU
Type 11 single panel radiator, 600 x 1400 millimetres, white enamel, 4455 BTU
Stelrad Halcyon Compact P+ Double Panel Radiator - 400mm x 1000mm
White 400mm x 1000mm Type 21 double panel radiator for central heating systems.
Stelrad Compact K1 Single Panel Horizontal Radiator - 700mm x 1800mm
Stelrad Compact Type 11 radiator 700mm x 1800mm, white
Stel Elite Radiator K1 - 600mm x 21 SEC 700mm
White K1 single panel radiator, 600 x 700 mm, BS EN 442, 700 W
Type 22 Double Radiator - 400 x 1000mm (4465 BTUs)
Type 22 double panel convector radiator, 400 x 1000mm, 4465 BTUs
K-Rad Kompact Radiator Type 22 - 500X1300MM
Kartell K-RAD Type 22 white double-panel radiator 500 x 1300mm
For central heating radiators, start with the system and the job spec, not the finish. A standard wet system usually keeps you in the same family of product, but the real checks are output, depth, and whether the pipework and wall space will take the size you want. On a tight swap, a slimmer panel can be easier to land. If the room needs more heat, you may need a deeper unit or a larger footprint. The install package matters too. Flue route, filter requirement, fuel type, and who’s signing it off all change what you should be buying.
Flat panel central heating radiators are the usual pick when you want a straightforward swap and do not need much depth off the wall.
If you need more output from the same footprint, a double panel or double convector version gives you that. The trade-off is depth. It sits further out and can be tighter on pipe centres and clearance.
Single panel units are slimmer and easier to place where space is awkward, but you give up output. Once you have fixed the room layout, Radiators is where you step back and compare the wider range against the job.
The first check is output against space. A deeper unit gives you more capacity, but it also stands further off the wall and takes more room around pipework, skirting and furniture.
On a straight swap, that often matters more than the finish. For tighter spaces or lighter loads, a slimmer panel is usually the cleaner fit. Column Radiators suit jobs where the look is part of the brief and you can live with the extra depth. Designer Radiators come in when appearance is driving the choice, but you usually give up some simplicity and sometimes some output for that.
Once you’ve picked the unit, the next call is what sits around it. If the room needs a cleaner finish, radiator covers are the usual add-on, but they do reduce output a bit and make access tighter when you’re back for a valve change.
Radiator foil is worth considering on older external walls where you want heat back into the room rather than into the masonry. For a neater install, radiator valves and the right parts and accessories matter more than people think - it’s usually the small mismatches that slow you down on site.







