Bill payers are being urged to submit a meter reading as household energy prices rise by 13% for millions of people in England, Scotland and Wales on Wednesday.

Anyone whose tariff is affected by regulator Ofgem’s price cap and does not have a smart meter should take a reading to avoid previous usage being charged at the new, higher rate.

Price rises, driven by the higher cost of gas, may have a relatively limited impact owing to warm weather and lower energy use during the summer months.

But higher energy prices caused by the fall-out of the US-Israeli war with Iran are likely to persist into the winter, according to analysts at the consultancy Cornwall Insight.

It has predicted a very slight 0.5% dip in Ofgem’s price cap in October, adding renewed pressure on the government to step in to help those in need.

Ministers point to reforms to cut bills earlier this year. Chancellor Rachel Reeves had also indicated some targeted support could be provided in the autumn, although she may be replaced in the job under new Labour leadership, and prices have not risen as high as feared before the US-Iran truce.

“The Iran ceasefire gave the markets some breathing room, but this is a pause, not a resolution to the conflict. What comes out of the final agreement, if there is one, will matter enormously for energy prices,” said Craig Lowrey, principal consultant at Cornwall Insight.

“Even in the best-case scenario, the enduring effects from the conflict will be with us for a while.”