Ask 10 people what temperature their home should be, and you'll get 10 answers, most of them delivered with total confidence. Somebody will mention 21C. Somebody else will insist their grandmother managed fine at 15C.
There's plenty of good guidance to be found on this subject, and it's more nuanced than being told a single number. Different rooms suit different temperatures, and the difference between the warmest and coolest rooms in your house is where a fair amount of money sits.
