Anyone heard of the BOT unit?

[EvTek23]

I came across this term for a unit of electricity, I'd never heard of it before.
The BOT, Board Of Trade unit is the same as 1kWh, which in 1903 would have cost you around 6 1/2 old p, equivalent to 2 1/2 p in decimal money.
We are talking the infancy of electricity, and the Bournemouth and Poole Electricity Supply Co were promoting its virtues for, Lighting, Heating and Motive power.
Electric cars were popular at that time, while trams were just being introduced.
I just loved the advert and it's wording promoting this new household and industrial wonder

 

[Rolfe]

I had an exam question at school in the late 1960s, and the answer was the price of 1 kwh of electricity. 6d. I presume that was what it actually cost then.

I'm now paying 8 1/2 p.