How many different electric circuits are there?

There are an infinite number of possible combinations to create an electric circuit.

It will simply not be possible to answer it correctly due to lack of information from absolutely all the developers around the world.

Even by limiting an answer to smaller circuits, this question is a challenge.

Even the simple light bulb is an electric circuit. How many different bulbs don't we find around the world these days? We have fluorescent bulbs, low voltage bulbs, high voltage bulbs, metal halide bulbs, halogen bulbs, this most likely in the thousands of different varieties from different manufacturers.

I would simply count on many many millions of different electric circuits. A lot of which would be similar work-wise, but still different maybe only by color.

This is only an educated guess that is in the area of many million's+ and then some.

By combining parts in order to make other circuits, the number grows unfathomable large pretty soon. The question only asks about what have been mad. Not what can be made. By this, we know the number can not be infinite, but we know the number to be large.

Each house around the world is an individual electric circuit. Each being different, however some more than others. We are 5 Billion people on this planet of ours. If there are 5 people in each house, then there must be 1 Billion houses with each a slightly different electrical circuit.