How many electric trucks fit on your grid connection?

It is the first question almost every transport company asks when it considers electric trucks. The answer is not on your energy bill. Your contracted capacity tells you the maximum you may draw, but not how much of it is still free at the moment your trucks want to charge.

Why the answer changes throughout the day

Your building does not use the same amount of power all day. During the day, cooling, lighting, offices and the workshop are running; at night, use is often much lower. The room for charging is therefore different at every moment: contracted capacity minus what your building uses at that moment.

Then there is the planning. A truck can only charge while it is at the depot, between returning and leaving. A truck that comes back at 18:00 and leaves again at 05:00 has eleven hours. A truck that stands at the depot for one hour between two trips has one hour.

What you need to calculate it

• Detailed metering data of your grid connection (quarter-hourly, half-hourly or hourly) for a full year, from your metering company or supplier.
• Trip data from your planning system (TMS): departure, return and kilometres per vehicle.
• Your contracted capacity and energy contract.
• Data on the vehicles you are considering: battery size, consumption per kilometre and charging power.

A worked example

Say you have a 100 kW connection and a building that uses 25 kW on average at night. Between 18:00 and 06:00, roughly 75 kW × 12 hours = 900 kWh is available for charging.

An electric tractor unit that drives 300 km a day at 1.2 kWh per km needs about 360 kWh. On paper, two of them fit: 720 kWh together. But consumption rises in winter, some trips are longer and the building does not use the same every night. That is why you calculate it in detail over a full year, not with averages.

What you can do when it gets tight

• Smart charging: spreading charging over the whole night instead of starting everything when the trucks return. It costs nothing and often creates the most room.
• Extra capacity at fixed times: drawing more at night, if your grid operator offers such a product.
• A stationary battery: charged during the day when there is room or the sun is shining, and used for the trucks in the evening.
• Solar panels: mainly useful when vehicles are at the depot during the day, or combined with a battery.
• A grid upgrade: the structural solution, but in many regions with long waiting times.

Costs count too

Charging at the busiest moment raises your peak, and in many countries you pay per kW of peak. A good calculation therefore shows not only whether it fits, but also what it costs: per kWh, per vehicle and over ten years, next to the same trips with diesel.

That is exactly what the Energy Scan does: your own trips, your own energy use and your own grid connection, calculated in detail.