I have a house full of 1960's panel radiators some single others double but I have no idea what their output rating is. I have worked out what output I need for each room and would welcome some advice on what output I might expect from rads that old to compare with the modern replacements. Can anyone advise me please ?

Drewruss

Old or new - radiators have been sized specifically to your room. New radiator output are greater than the old once size for size, due to improvements in design etc.

BTW

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i would say modern radiators are similar with doubles just double with fins about 40% more but thats just a guess

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Whether what was considered adequate in the 1960s is still deemed adequate is another question . Fifty years ago most people were satisfied with much less heat than most folk are now. Central heating was then considered a luxury, now it tends to be considered an essential.