On 28/08/2019 17:59, John wrote:
If I change a conventional (horizontal) radiator for a tall vertical one of
the same BTU / Wattage, will there be any differences in the heating
effect?

Not really, but the heated air won't follow the same path which may be
awkward. Because they're taller and narrower, the patch of ceiling
above the radiator will be smaller and hotter which may or may not matter.

I have a couple of 3kW verticals - big buggers - in the kitchen and
hallway and they both work well, but kitchen one is higher output than
the conventional radiator it replaced.

They're also a lot more expensive and heavier, but you do regain a lot
of dead wall. They look better IMO too.

Cheers
--
Clive