You are assuming that the economy can smoothly scale down with energy restriction. In reality, everything is highly optimized, with "just in time" supply chains

You are assuming that the economy can smoothly scale down with energy restriction. In reality, everything is highly optimized, with "just in time" supply chains with little safety margin. Once energy demand greatly exceeds supply, the whole system collapses. And most transport and heating does not use electricity, so the problem is actually worse than 27.6% of normal supply.