A site with one charger at sixty percent utilisation looks like an obvious case for a second. It frequently is not — sixty percent averaged across a day can mean two saturated hours and twenty-two empty ones, and a second unit will spend those twenty-two hours depreciating.
The question is not how busy the charger is. It is how much demand is being turned away.
Signal one: turn-aways, not utilisation
The number that matters is arrivals at an occupied charger. Most operators cannot see it, because a driver who finds the bay full simply leaves and no record is created. Three imperfect proxies, in descending order of usefulness:
- App sessions where a driver viewed the site while every connector was occupied, and no session followed.
- The share of hours the site is at full occupancy. Above roughly fifteen percent of operating hours, you are consistently turning people away.
- Repeat drivers whose visit frequency drops after a period of high occupancy. They found somewhere else.
Signal two: the shape of the day
Plot occupancy by hour across a month. Three shapes, three different answers.
| Shape | Means | Do |
|---|---|---|
| Broad plateau across many hours | Real sustained demand | Add the second unit |
| Two sharp peaks, empty between | A scheduling problem | Try pricing before capex |
| One peak, growing month on month | Demand arriving | Wait one more month, then add |
The middle case is where money gets wasted. A time-of-day discount that moves fifteen percent of sessions out of the peak costs nothing in capital and often removes the constraint entirely.
Signal three: what the grid connection allows
A second charger behind the same sanction either needs more sanctioned load, which is slow and expensive, or load management, which is neither. Where load sharing is viable, the second unit is dramatically cheaper than the first and the threshold for adding it should fall accordingly.
The one thing to do at the first install
Leave spare ways in the board, conduit in the trench and physical space at the panel. It costs very little during the original civil work and turns the second-charger decision from a project into a purchase order.