Hall of Power · Catalogue 06
⚡ The Watt Exchange
Energy literacy in the only currency that needs no conversion: bananas, stairs and phone charges. Decode any item, your monthly meter, and the kinetic energy of a moving car (E = ½mv²).
Exhibit A · Energy in things you already know
What is hiding in this?
Why this matters. Few people know that a litre of petrol holds about
75 bananas of energy — or that your phone battery is a tiny fraction of one. When a headline says
"the grid stored X megawatt-hours," this is the translator you were missing: one MWh is the food of about
280 humans for a day.
Exhibit B · Your meter, decoded
What did your last bill actually buy?
The scale is the point. A month of home electricity is roughly the food energy of
a hundred days of eating — but moving, heating and making things take far more than bodies do.
That gap is why your "energy bill" is really a fossil-fuel bill, and why efficiency beats frugality.
Exhibit C · The physics of a moving car
Kinetic energy, in bananas
E = ½mv². The velocity is squared: double the speed means
four times the energy, so every emergency stop is a lesson in exponential risk. Stopping a car is
throwing away a banana's worth of energy — into the brakes, as heat. That's why braking downhill, or
stopping in traffic, is where the fuel goes.
Approximate figures, honestly rounded: banana ≈ 450 kJ (105 kcal · 1 kcal = 4.184 kJ);
petrol ≈ 34.2 MJ per litre; 1 kWh = 3.6 MJ exactly; human food ≈ 10 MJ/day (2,400 kcal);
UK grid carbon ≈ 0.2 kg CO₂ per kWh (2024 average, falling with renewables); EV efficiency
≈ 6.4 km per kWh. Treat every number as "the right size", not "the exact figure".