Sustainability Energy Mobility29 April 20261 min read
The car in the driveway is the biggest battery you own
Bidirectional charging finally works in practice - with one condition most people miss.
A mid-size electric car carries somewhere between 60 and 80 kilowatt-hours. A generous home battery carries ten. The car is parked at home for most of its life. The arithmetic has been obvious for a decade; what was missing was the plumbing.
That has largely arrived. Bidirectional wallboxes are on sale, several manufacturers have unlocked vehicle-to-home on cars already in driveways, and the grid codes in most of Europe now describe how it should behave rather than whether it may. A house can run on its car through an evening peak and recharge it overnight at the cheap rate.
The condition people miss is that the car has to support it, and support is per model and often per model year rather than per brand. A wallbox that can do it and a car that cannot is an expensive socket. Check the vehicle first, then the box.
The second question is one nobody can answer for you: how much of the car's range you are willing to spend on the house. Most systems let you set a floor - keep 60 percent for driving, lend the rest to the building. It works well until the week you need an unplanned long trip, which is precisely why the floor is adjustable.
