How many chargers does a residential building need?
Fewer than the number of bays, more than most projects allow for, and the honest answer is that nobody knows the final figure at design stage.
The practical approach is to split the question in two. First, how many bays get a charger on day one. Second, how many bays get the cabling and electrical capacity to add one later without opening the ground up again.
The second number matters more than the first. Adding a charger to a bay that already has a cable run is a short job. Adding one to a bay that does not means trenching, ducting and possibly a new distribution board. Buildings that plan for a low day-one count but a high future count avoid that.
What does EV charging do to a building's electrical load?
This is the constraint that actually limits the design, and it gets underestimated.
A single AC charger is a modest load on its own. The problem is that residents tend to plug in at the same time, in the evening, when the building's other loads are also at their peak. Ten chargers all drawing full power at 7pm is a very different thing from ten chargers spread across the day.
There are two ways to deal with that. The expensive one is to size the incoming supply and distribution for every charger running flat out at once. The sensible one is load management: chargers that share the available capacity, so total draw never exceeds what the supply can deliver, and each car still gets charged overnight.
Wallbox chargers handle this through Dynamic Load Management. A Wallbox energy meter monitors the building's demand against its maximum allowable value and gives the chargers whatever capacity is left. When the building is close to its limit, charging slows; when demand drops, it picks back up. It needs the energy meter installed and a Cat5e data cable between the meter and the chargers, so it belongs in the electrical design rather than being added later.
Either way, the decision has to be made when the electrical design is done, because it sets the size of the incoming supply and the distribution boards.
Single phase or three phase?
Three phase where it is available, which in most Saudi commercial and larger residential buildings it is.
A single-phase charger is limited by the phase it sits on. A three-phase charger draws across all three and charges the car considerably faster. For a villa with one or two cars the difference may not matter overnight. For a building with a shared car park it matters a great deal, because faster charging means bays turn over and fewer chargers serve more cars.
AC or DC charging?
For a residential or office building, AC. Cars sit for hours, AC charging is cheaper to install, and the car's own onboard charger does the work.
DC fast charging is for places where the car needs to leave quickly: fuel stations, highway stops, fleet depots. It costs several times more per bay and puts a much heavier load on the supply.
Wallbox makes both. Its AC range includes the Pulsar family for homes and Commander 2 for shared and business use, and its Supernova range covers DC fast charging for high-turnover sites.
What about villas?
A villa is the simplest case and the one where getting it wrong is most avoidable.
The charger sits in the garage or carport, on its own circuit from the main board. The decisions are whether the board has spare capacity, whether the cable run is planned before the walls are finished, and whether the owner wants one charger or two. All three are easy to settle at design stage and awkward afterwards.
If central vacuum piping is going in at first fix, run the charger cable at the same stage, while the walls are still open.
When does this need to be designed in?
With the electrical design, which means early. The incoming supply size, the distribution board layout and the cable routes to the car park all depend on the charging decision, and all of them are expensive to change once the building is up.
The pattern to avoid is the one that is now common: the building completes, residents buy electric cars, management installs chargers one at a time on whatever spare capacity exists, and the building runs out of capacity at the fourth or fifth charger with no cheap way to add more.
Centra reviews the electrical drawings and returns a charging layout with a bill of quantities.