It started with two competing systems

In the 1880s Edison’s direct-current networks served a few blocks around a power station, because DC does not travel well. Alternating current, championed by Westinghouse and Tesla, could be transformed to high voltages, sent for miles and stepped back down. AC won, but not everywhere at the same voltage: existing 100–120 V systems kept their bulbs and appliances, while countries building fresh grids chose 220–240 V because thinner copper carried the same power, which was cheaper.

That single decision still explains the deepest split in the world’s electrical map. Countries that were early and wealthy kept the low voltage; countries that electrified later, or were buying equipment from a European supplier, went high.

Frequency followed the same path

America settled on 60 Hz, Europe on 50 Hz, and Japan managed to acquire both: Tokyo bought German generators at 50 Hz, Osaka bought American ones at 60 Hz, and the country has run two grids ever since. The boundary still divides Japan into two halves that can only exchange a limited amount of power through converter stations.

Then came sockets

Early outlets were two flat blades or two round pins, shaped by whichever manufacturer got there first. As current ratings and safety requirements grew, each country added earthing in its own way:

  • Germany, 1926 — Schuko added earth contacts to the rim of the socket. Symmetrical, simple, and now used across most of Europe.
  • France — put the earth pin in the socket instead of the plug, so the plug can be smaller.
  • Britain, 1947 — rebuilt domestic wiring around a ring main and a fused, chunky thirteen-amp plug (Type G). Shutters and an earth pin that opens them made it arguably the safest design, and one of the hardest to adapt to.
  • Denmark, Italy, Switzerland, Israel, Australia — each kept its own pin geometry, sized and spaced for its own appliances.

By the time an international standard was drafted — Type N, published by the IEC in 1986 — every country already had factories, tooling, building codes and millions of installed sockets. Brazil and South Africa adopted it in part. Nobody else did.

Why nobody fixes it now

Changing a plug standard means changing every socket in every building, and every appliance in every shop, at once. The cost is national and the benefit is mostly enjoyed by foreign visitors. There have been partial attempts — South Africa’s 2013 move to add Type N, Thailand’s 2006 introduction of Type O — and each of them left the old sockets in place.

The result is the map we have: 15 types, two voltage classes and two frequencies, with a handful of genuine oddities that catch travellers out. Jamaica runs 110 V at 50 Hz. The Philippines runs American plugs at 220 V, 60 Hz. Thailand’s sockets often accept American, European and Thai plugs in the same face.