Steel vs Aluminium vs Cast Iron Radiators

Aluminium radiators have the highest heat output per kg — aluminium conducts heat 5 times faster than steel and 10 times faster than cast iron. A typical aluminium radiator gives 180-220 watts per section vs 120-160 watts for steel panel and 40-80 watts per section for cast iron (though cast iron sections are larger).

Yes. Heat pumps run at lower flow temperatures (35-45°C vs 60-75°C for boilers). Aluminium radiators respond faster and give better output at low temperatures, making them ideal for heat pump systems. Cast iron radiators are the worst choice for heat pumps due to slow response and high water volume.

Cast iron radiators cost more due to the heavy raw material, energy-intensive casting process, and the weight/cost of shipping. They are often sold as premium or heritage products. Reclaimed Victorian cast iron radiators can cost £200-800+ per unit. New reproduction cast iron radiators start at £300-500 per unit.

Quality steel panel radiators (Stelrad, Henrad, Myson) last 15-25 years in a properly maintained system with inhibitor. The main failure mode is internal corrosion from sludge build-up. Cast iron radiators can last 50-100+ years. Aluminium radiators last 20-30 years but are sensitive to pH — the system water must be maintained at pH 7-8.5.

Technically yes, but mixing aluminium with other metals increases corrosion risk through galvanic action. If mixing, use a good quality inhibitor (Fernox F1 or Sentinel X100) and maintain it. Ideally, stick to one material throughout the system, especially if using aluminium.