Electric parts were used to either generate electricity or consume them to perform specific actions. They can only only found in blueprint editing or saves from before 1.5.
All electric parts are currently being reworked and are temporarily removed, with the exception of the Ion Engine and the Solar Panel. Wheels and ion engines don't need electricity to work and both variants of Solar Panel don't generate electricity.
When 1.4 quicksaves and blueprints are converted to 1.5, removed electric parts are turned into grey blocks.