Charging within your contracted capacity: load balancing or EMS?
By Maarten Alta · 8 November 2026
Four trucks return from their day shift at 17:00 and plug in. Each charges at 150 kW. The building still uses 80 kW at that moment. Together that's 680 kW, while your contract may be 200 kW. Without control, you go far above your contracted capacity. That costs money, and on a full grid connection it simply isn't possible.
The good news: the trucks only need to be full the next morning. There is a whole night in between. With control, it often fits.
Which limit counts?
The limit is your contracted import capacity: the capacity you agreed with the grid operator for drawing power. Not your export capacity, and not what your connection can physically handle. Your connection is often larger than your contract. Go above the contract and you pay more, and if it happens repeatedly, the grid operator raises your contract.
The room for charging is per quarter hour: contracted capacity minus your building's use at that moment.
Load balancing: the charging system controls
With load balancing, the charging system shares the available power among the chargers. It measures your building's use and only gives the chargers what is left. A worked example:
- Contract 200 kW, building 60 kW in the evening: 140 kW of room.
- After 20:00 the building uses only 20 kW: 180 kW of room.
- Three trucks each need 200 kWh, 600 kWh in total.
- From 17:00 to 20:00, 3 × 140 = 420 kWh fits, and much more after that. It fits easily.
Load balancing is enough if you only have chargers, or chargers with solar panels. The system controls the charging, not the rest of your installation.
EMS: controlling everything together
Once you add a battery, you need an energy management system (EMS). An EMS controls building, solar, battery and chargers together:
- The battery charges when there is room or when the sun shines, and supplies power when building and trucks together threaten to exceed the contract (peak shaving).
- Charging can follow the sun or a dynamic power price.
- The EMS schedules charging so the trucks are full on time, with a margin in case it gets unexpectedly busy.
An EMS can do more, but is also more complex and more expensive. Choose it if you have or are considering a battery, or want to steer on prices.
Where it still gets tight
- The building itself sometimes already exceeds the contract, for example because of cooling or a workshop on a busy day. Then controlling the charging no longer helps: that quarter hour is too heavy because of the building.
- Trucks with short depot stays, such as between two shifts, have little time to charge. Then control gets tight.
- Peaks on one day a week, such as a busy Monday morning, set your monthly peak charge. See One quarter hour sets your grid costs.
Calculate it first
Whether load balancing is enough, or whether you need a battery and an EMS, you calculate with your own quarter-hourly data and trips. The Charging Scan calculates both: load balancing (with and without solar) and EMS with a battery (with and without solar). You see per week whether charging fits your contract, how much charging shortfall there is, and what each scenario costs per year.