I don't think it can be qualified in percentage terms like that really, you need to consider along with other cost savings or increases, like:
Travel impact (will you need a car/newer car/more petrol/get rid/less petrol?).
Heating (is it flashy & modern, or a lovely old detached cottage that leaks heat).
Council tax band / insurance impact of area (car most importantly, it could easily rise quite a bit pending postcode, unlikely to drop!).
There's others, but basically if you more to a nice crime-free area into a nice well-insulated house, then spend more on rent (and you'll probably be forced to), go the other way, then you'll need more in back pocket.
(...and it is a bit of an odd OP to be fair!)