How does selling surplus electricity work?

If you have a photovoltaic system but do not use all the electricity it produces, you can sell the surplus. You do this by signing a production contract with your electricity supplier, who then undertakes to buy the electricity you do not use yourself. Most commonly, electricity companies pay an hourly price based on the Nordic electricity exchange Nord Pool’s electricity spot price, i.e. what the electricity costs to buy on the market in the current hour.