We are currently part of the EU; we have participated in setting the EU standard and have agreed to follow it. Once we have left the EU (when and if), we can use whatever size of energy-wasting cleaners our Parliament decides.
No, that's not true. He says that if the EU standard is, for example, 500W; and the UK standard is, for example, 10kW, we can't expect our standard to be acceptable to the EU, so we can't expect to be able to freely export products to the EU that don't meet EU standards. Neither can we expect to have any control over what the EU standards are, after we have resigned. If we don't like them....
Brexit means Brexit, as somebody once said.