The Centre for Competition Policy at the UEA has found that half of the population have never switched gas/electricity suppliers, and are paying more than they need to accordingly. Further, even some that have switched have done so for the wrong reasons so that they, too, are paying over the odds. Their report is here. And we've had full consumer choice in gas and electricity for ten years now, one of the great achievements of John Major's much-maligned government.
On the plus side of this sorry but somehow inevitable story is the well-known economic phenomenon that you only need competition at the margins for at least some benefits to be felt across the market as a whole. In this case, we can be fairly sure that prices for even the inert 50% are somewhat lower than they would have been without the competitive market framework.
On the negative side, we can be equally confident that those who can least afford to pay over the odds will feature disproportionately amongst this 50%.
As ever, the Bible articulates the chilling truth:
To them that hath, shall be given. And from them that hath not, even that which they have shall be taken away.