Is there actually any consistency about how warm a given TOG value keeps you?
The first (and only) duvet I ever bought was from Tesco and I just picked the highest TOG one because the price was the same for all. I think it was a
12 or maybe even higher. It was ok but not exactly roasting. A bit too hot in summer and a bit too cold in winter.
When I moved into my new house last year some friends very kindly donated a single bed, duvets and all the linen because my removal company had screwed everything up and most of my stuff was still in storage. One duvet is a 4.5 and the other a 6. The 4.5 one is really light and feels a bit like you're only sleeping under a sheet. It's better if I put a big towel on top which gives it enough weight to feel comfy but it's no way near warm enough in winter. In the summer it's fine.
The 6 TOG one despite the supposed minimal increase in TOG value one is boiling. Much heavier so it snuggles down round you nicely and so warm that I have to turn the radiator off and keep the temp down to 15c in winter or I wake up sweating. I've never been cold under that duvet even when it's 7c below zero outside.
So I don't see much consistency in thermal performance here even though the TOG value is supposed to be a scientific measurement. A 12 TOG duvet that behaved in proportion to my 6 TOG one would parboil me alive even though the Tesco one was less warm than my current 6.
So what gives?