It doesn’t much change your calculations, but if you charge at home in the UK (we trail a cable across the pavement with a low-profile cover) then the electricity _is_ all but free.

We pay 7.5p/kWh for 6 hours overnight, but we also get £5 per month back (if we charge at least 10 hours) in return for having charging interrupted for up to an hour each night when the grid has least capacity. I drive about 7000mi/year, which means I’m paying about 1p/mile on average for home charging.

(The £5/month is from the charger manufacturer, SyncEV).