If it much more than doubles then realistically there'll have to be political intervention because it's not just a case of "people will struggle to pay it" - people simply won't be able to pay it, won't pay it, will go into massive energy debt that the companies will be unable to reclaim any time soon, and they'll bust.
Put it this way... let's say a young family ends up with a £3000 energy debt, their living situation becomes unmanageable and they end up moving in with parents. All that can happen to that £3k debt is that it gets bought by a debt collector for a fraction of what it's worth, and then the struggling family sets up a token payment of £20 a month or whatever. The energy company barely sees a sniff of that £3000 debt. Ever. They have no other legal avenue to go down, there are rules about debt collection and affordability.
Multiply that by a million families
.