Do you need larger cast iron radiators with a heat pump?

Cast iron radiators are often a touch bigger on a heat pump than they’d be on a gas boiler, though not always by much, and not necessarily a different radiator altogether. Because you can add sections to most Paladin models, getting more output usually means lengthening the radiator you already like rather than swapping it out.

Browse our cast iron radiators range to see the height and section options for each style.

Estimated reading time: 3 minutes

Not every cast iron radiator is going to need a size change for a heat pump. If a room’s already warm and comfortable with its current radiator, and the room’s reasonably well insulated, there’s a good chance it can stay exactly as it is. It’s the poorly insulated rooms, or the ones that always felt a bit cool anyway, where a bigger radiator usually makes the difference. So it’s worth getting a proper heat loss calculation done, rather than assuming every radiator in the house needs replacing.  

Adding sections is usually all it takes with cast iron, rather than buying a completely different radiator. Because each section adds its own surface area, lengthening a radiator by a section or two is often enough to reach the output a heat pump needs. That’s a genuine advantage over some other radiator types, where getting more output can mean swapping to an entirely different model.

Here’s how that compares across the more common radiator types:

If you’re not sure whether your rooms need bigger radiators or just a few more sections, our radiator configurator gives you a proper answer, room by room. And if you’d rather talk it through, our team’s happy to walk you through it.