The Energy Price Guarantee doesn’t finish in April, as the Autumn Statement extended it for a further year, so that it is now planned to finish in April 2024.
However in April next year, the effective cap on the average household bill will rise to £3,000 per annum from the current £2,500, if of course the OFGEM price cap level still sits above £3,000 next April. If the OFGEM price cap falls below £3,000, then the government guarantee scheme would become redundant.
For reference the OFGEM cap level for January to March next year has been set at £4,279, so there would need to be a major, major drop off in wholesale prices in the next couple of months for the OFGEM cap level for the April to June period next year to fall below the £3,000 level. In fact, given what’s happened to wholesale prices since this cold snap hit, it’s likely that the OFGEM cap level will increase in April next year. So the government guarantee price will very likely be needed, and therefore for your average punter that means a 25% increase in prices next April.
Also, it’s not quite true that prices can’t rise next month, although I’m splitting hairs here a bit. The government has published the maximum per unit rates suppliers can charge as part of the guarantee scheme for Q1 next year - these effectively replace the OFGEM price cap levels - and some of these will increase fractionally in January, but the impact will be very small for the average person and they’re still consistent with the £2,500 annual bill. And of course suppliers don’t have to change their tariffs if they don’t want to, but most will presumably adjust them to the new maximum levels.