The hydro meter does not count joules — it would need nine digits by breakfast. It counts kilowatt-hours: $E = Pt$ (read aloud: E equals P t) — the energy $E$ the appliance used, the power $P$ it draws, the time $t$ it ran for — with the power in kilowatts and the time in hours, so $E$ lands in kWh. One kWh is 1000 W held for 3600 s, so $1\ \mathrm{kWh} = 3.6\ \mathrm{MJ}$ — this chapter's ×3.6 bridge, the same 3.6 as the km/h one, wearing a much bigger prefix.

Ontario prices electricity by the time of day — off-peak evenings and weekends cost the least, which is why the dishwasher runs at night. The rule that saves marks is the same as ever: convert BEFORE the multiply. Watts become kilowatts first, then the hours come in, and the answer lands in the unit the bill actually charges for.