WHEN EUROPEAN regulators were tweaking the continent’s wholesale electricity markets some years ago, they added a price floor to short-circuit trading snafus. At minus €500 ($580) per megawatt-hour (MWh), it was more of a price basement. It was set so low in order to be triggered only in exceptional circumstances. May 1st, when bright sunshine and strong winds met low demand for electricity from Europeans enjoying a public holiday, may have seemed pretty ordinary. Yet the wholesale electricity price in Germany reached minus €499 per MWh. If this translated into retail prices, you would pocket €50 for charging your electric car.
