How the home charging cost calculator works
Where the watts go
Your car consumes energy at its efficiency rate — miles per kWh, typically 2.5–4.0 for mainstream EVs. But the meter measures what the wall delivers, and 8–15% of that is lost to charging conversion and battery conditioning. The calculator charges you for the wall, because that is what the bill does.
The rate is the whole game
At the US average of ~17¢/kWh, a 3.3 mi/kWh car costs about 5.2¢ per mile at home — roughly a third of a 30 MPG car at $3.60 gas. But the spread in rates is enormous: from under 10¢ in some markets to 40¢+ in others, and time-of-use overnight windows routinely undercut flat rates by a third. Find your real rate on the bill — it is usually printed as an all-in ¢/kWh.
Making the number smaller
Three levers, in order of size: charge overnight on a time-of-use plan, keep charging losses low (Level 2 beats trickle charging in cold weather), and drive gently — efficiency swings 15–25% between aggressive and mellow highway speeds.