[thyristan]

It doesn't, for reasons of price.

For consumers, power prices consist of the actual price of power, plus network fees. Network fees are fixed at (on average) something like 10ct/kWh or 100€/MWh. So negative prices are only really negative if the power price drops below those -100€/MWh, which rarely happens (the usual dips are at low single-digit cents per kWh).

And even then, there is the issue of network fee double-dipping: Depending on the contract you have with your power company, the size and kind of storage you are operating, and the phase of the moon and your donations to the ruling party, you will be charged network fees twice, once when buying the power, once when selling it again. In that case, the threshold would be even worse, at -200€/MWh.

And all that doesn't factor in the cost of the storage infra.

Edit: And there is another factor: The current very low dip is in the intra-day prices. But contracts for consumers use day-ahead prices, which usually don't include those very large dips that result from miscalculations of weather and dispatch capacity.

Edit2: Just check https://tibber.com/de/preisrechner (use e.g. 10119 as Postleitzahl) and scroll down for the graph. Today, they give a negative day-ahead price of -1.5ct/kWh, but including network fees, taxes and their cut, you still end up paying 18.2ct/kWh...

[Majromax]

If you're buying and selling the power, then you don't care much about the absolute price, but rather the delta between the purchase and sale prices.

Below -100€/MWh, you don't need to sell the power to profit; you'd make at least some money just using it to heat up a big resistor.

[thyristan]

You didn't read what I wrote. The news is about trading prices. End users never pay those, because there are fixed network fees to be paid on top. So the actual bill will practically never have a negative price on it anywhere.

And even if there were negative end prices happening: There are metal smelting works and other operators of big resistors who will happily heat up even more. So prices will probably never get so negative that a normal consumer can ever profit from them.