A photovoltaic plant on your roof generates electricity ecologically and pays for itself. It even earns you a good profit.

Photovolatics is the conversion of sunlight into electrical energy by solar cells made of silicon. This technology enables your house to generate electricity. A solar system for a single-family home consists of one or more solar modules and a current inverter that converts direct current into alternating current and feeds it into the house electricity network.

That is straightforward enough. The problem is: on sunny days, your system generates more and on cloudy days less electricity than needed. A functioning storage battery for storing excess electricity has not been invented yet.

The solution: You supply the excess electricity directly into your local supplier network.

A good deal, because the government subsidises your environmentally beneficial electricity generation.