A long, long time ago, before the wind, before the snow — well, the middle of the 1800s to be exact — electricity was an intriguing but mostly useless thing. Some factories and residences toyed with early electric lights and motors powered by on-site generators, but most of the world used piped steam and natural gas to heat their homes and drive their machines for decades after electrification began. That would all change, however, with Nikola Tesla’s invention of three-phase high-voltage power distribution at the end of the 1800s and the creation of the world’s first synchronized national electricity grid in Great Britain in 1938.

Overnight, electricity became cheap and constantly available — it became a utility — and the number of users in the UK shot up dramatically, from around 750,000 in 1920 to 9 million in 1938. Synchronized electricity — 50Hz from every socket in the country — meant that devices (radios, TVs, motors) worked everywhere, and the production and sales of those early electric devices boomed accordingly. Other countries would soon follow, and eventually, thanks to intra- and international interconnections between networks, the world’s power grids are now mostly synchronized at either 50 or 60Hz.

A modern power grid is a wondrous thing. Basically, through the magic of high-voltage direct-current (HVDC) cables, electricity generation and consumption can be balanced across an entire country — or even an entire continent. If you need power down south, you can spin up a hydroelectric generator in the north; if you have excess power in the south, you can use it to pump water back up to the top of the dam in the north. If it’s particularly windy or sunny, you can turn off a few coal and combined cycle gas turbine (CCGT) power plants. If a neighboring country or state is being hit by a heatwave, you can pump power into their grid via an interconnector. If you have a lot of constant nuclear power generation (like France), you can export surplus power to other countries — and then, during peak times, import power from those same countries if you ever need it.

Perhaps most impressively, though, it’s important to remember that the world’s electricity grids have almost no energy storage at all. With the exception of pumping water back to the top of a hydroelectric dam — an option that’s only available in limited quantities and only in some countries — all electricity generated must be consumed immediately. As you can imagine, spinning up exactly the right number of turbines to match the power needs of millions of people is rather difficult — and in the UK, it’s all done by a single person.

As you can see in the video above — which is one of my favorite videos of all time, incidentally — you can see that it’s one person’s duty to make sure that the electricity generation of the UK matches up perfectly with the consumption of its 60 million tea-drinking inhabitants. There is a little bit of wiggle room built into the system — the 50Hz frequency can be reduced or increased slightly to compensate for energy shortfall or surplus — but the guy generally has a few seconds to spin up a turbine or beg France for power before the whole thing comes tumbling down.

In May 2008, a series of issues led to the UK’s national grid electricity frequency falling to 48.792Hz — way below the system’s 49.5Hz “safe zone” demarcation and low enough that power had to be cut to hundreds of thousands of homes until enough power generation could be brought online to restore the frequency.

Not all grids are created equal

If the video or this story has piqued your interest in power grids, I encourage you to take a look at two websites: The real-time status of the UK national grid, and the real-time status of the French national grid. While we’re not going to delve into the sticky topic of electricity mix, these websites show you how two fairly similar countries have a completely different approach to power generation. You can see that France, which built a ton of nuclear reactors following the 1973 oil crisis, is almost entirely reliant on nuclear power, with hydroelectricity (from the Alps in the south) providing some flexibility. The UK, on the other hand, uses a much more conventional mix of coal, gas, nuclear, and renewables (the UK is the world leader in offshore wind power generation).

France’s reliance on nuclear power is both good and bad. It’s good in that France’s power generation is incredibly stable (you can’t turn nuclear plants on and off very easily) and almost completely unaffected by global fossil fuel price fluctuations — but it also means that France lacks the ability to significantly step up on-demand power production (during a heatwave, for example). If you look at the “Monthly Germany/Belgium/UK” graph, you can see that France is intermittently importing gigawatts of electricity from Germany to cover any national shortfalls, while at the same time constantly exporting a constant 2GW to the UK (more on that in a second).

The UK has a much more conventional setup, with nuclear power providing a solid baseline, coal and gas being spun up during daylight hours, and then hydroelectricity being used to cover burst/peak power (as illustrated by the “TV pickup” in the video). As you can see, except for the height of winter — when local coal plants are fired up — the UK imports a constant 2GW from France (this is a long-term shortfall that needs to be rectified with some new power plants). This power is provided via the bi-directional HVDC Cross-Channel cable, which was completed in 1986 and is still the largest submarine cable of its kind.

Next page: The super smart grid