Like today, back in the 1780s there was a change in the way machines were being powered. Then it was from horse power to steam power, for driving pumps to take water out of mines.

Young James Watt had trouble convincing industrialists that his steam engines could save them money. So he set about doing experiments to work out how much power a horse could produce.

He decided that a fair figure for a “Brewery Horse” was to lift a 550 lb weight 1 foot every second. This got rounded off to 33,000 foot pounds per minute. So, the “Horsepower” was born. Don’t you love the imperial system? We have been stuck with the Horsepower ever since.

Watt sold his steam engines by quoting how many Horsepower the engines would produce and so how many horses the machine would replace.

Meanwhile, on the other side of the English Channel, revolution was afoot. Aristocrats were having their heads guillotined off and new forms of government were being tried. Out with the old and in with the new!

French scientists had been beavering away for 100 years or so on a rational system for length, weight and volume based on 10s and now seemed a good time to slip the idea in front of some ranting revolutionaries. In 1799 a decimal system based on the kilogram and the metre was officially introduced. Then thrown out … Then reintroduced. After the 3rd revolution it was still a going concern. However, the French tendency to man barricades has never faded.

Back on the English side of the channel, scientists could see the sense in this metric lark and thought that they should get some naming rights.

The units should be named after famous scientists. There was the Amp (Ampere, French Scientist) and the Volt (Volta, Italian Scientist), but the power needed to push an Amp through a potential of a Volt was up for grabs. The British Association for the Advancement of Science thought that Watt should be the unit, and so it was. Now Watt was actually Scottish, but at least he was on the right side of the channel.

Now the metric system has been adopted all over the world, except for three countries: Liberia and Myanmar, and the USA. I say nothing.

So what the hell has all this got to do with EVs? Well, in EVs, the mechanical power and electrical power are defined in the same units. Watts. 1 Watt is quite a small amount of power, so we generally see power measured in 1000 Watt chunks, or Kilowatts (kW). If your home charger is filling your EV at 7kW for an hour, then your battery is going to get 7 Kilowatt-Hours (kWh) of extra energy. Mechanical power and electrical power are measured in the same units (kW). The maximum mechanical power produced by the motor in our MG4 is 125 kw. That’s about 167 Horsepower in the old money.

I know Watts is a much more rational metric until, but James Watt’s marketing gimmick lives on when I think of my car being pulled by 167 horses snorting, stamping and farting their way up Bulli Pass. That’s serious grunt!