Harry Bloomfield, Esq. wrote:
Theo has brought this to us :
I now live somewhere without gas so I haven't done it recently, but
previously it was always cheaper to get gas and electric from different
suppliers.

I have always heard that generally the opposite is true, dual fuel
cheaper from one single supplier.

I think it depends on usage. Dual fuel discount is usually £20-30. If
you're a low user, that makes sense. If you use a reasonable amount, the
difference in unit costs outweighs that. Given typical bills can be ~£1Kpa
it doesn't take a huge difference in unit cost to outweigh that £30.

Theo