How many street lights does Madrid have?

How to get close to this number

Work from street length and spacing. A city of a few million has thousands of kilometres of streets, and street lights sit roughly every twenty-five to thirty metres. Thousands of kilometres divided by thirty metres gives a figure in the hundreds of thousands.

The per-capita comparison in the explanation is what makes this city notable: among the highest in Europe, and the city has long been noted for how brightly it is lit at night. Lighting levels are a cultural and political choice as much as a technical one, and a city that stays out late lights its streets accordingly.

The LED figure is the practical payoff: the conversion cut street lighting electricity use by roughly half. Municipal lighting is one of the largest single line items in a city's energy budget, and a technology swap that halves it is the rare infrastructure upgrade that pays for itself while changing nothing a resident notices.