Smart charging and time-of-use tariffs
Shifting energy to the cheapest and cleanest hours.
- Explain smart charging and time-of-use tariffs clearly and accurately
- Read the numbers that define the behaviour
- Apply the idea to a real charging session
Overview
An EV is a large, flexible, patient load. That flexibility is worth real money on a time-of-use tariff.
In depth
How scheduling works
Either the car or the charger holds the schedule. Pick one and disable the other — competing schedules are the single most common cause of a car that mysteriously did not charge overnight.
Charging Cost Calculator
What a session costs at the wall, including charging losses.
cost = capacity × ΔSOC ÷ 100 ÷ efficiency × priceYou pay for energy measured at the meter, not the energy that reaches the cells. Dividing by efficiency accounts for the difference.
Example: 60 kWh × 60% ÷ 0.9 = 40 kWh billed. At 0.12/kWh overnight that is 4.80.
- AC home charging is typically 85–92% efficient end to end; DC rapid is 92–96%.
- Some public networks bill by time, which penalises cars that taper early.
- Compare against fuel using cost per 100 km, never cost per fill.
If the car and the charger both hold a timer, the overlap window is the only time charging happens — often nothing at all.
Key takeaways
- Off-peak charging is the biggest running-cost lever.
- Hold the schedule in the car or the charger, never both.
- Flexible load also reduces grid carbon intensity.
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