For a couple of hours last week I was paid to use electricity. Price of eletricity goes negative fairly often, but only a little. On top of the electricity I, having a spot priced contract, pay a margin ~0.5 € cents/kWh and tax and transmission fee. Last two are about 3 cents /kWh. So for me to get paid the price has to be about -7¢/kWh and that has only ever happened during a few hours.