What an EV load management system does
Each charger normally needs its own share of capacity at full power. A load management system sets one limit for a group of chargers and splits it between the cars plugged in. When many cars charge, each gets less. When few do, each gets more.
Static vs dynamic load management
| Static | Dynamic (adaptive) | |
|---|---|---|
| How the limit is set | A fixed limit for the charger group | Changes with live building load |
| Extra hardware | Usually none beyond networked chargers | A meter or sensor at the service or panel |
| Fits | Steady loads, dedicated EV panel | Shared services with big daily swings |
| Trade-off | Leaves some capacity unused | More setup and commissioning |
Chargers per amp of spare capacity
EV charging is a continuous load, so circuits and feeders are sized at 125% of the charger's set current. That gives a simple way to compare options:
- Without load management: chargers ≈ spare amps ÷ (charger amps × 1.25).
- With load management: the group shares a limit set below the spare capacity. Charger count is limited by the minimum current each car needs and by how long cars stay parked.
Load calculation and code
An electrician or engineer reviews your service size, existing loads and, where available, demand data from utility bills or meter data. The California Electrical Code is based on the National Electrical Code (NFPA 70). Article 220 covers branch-circuit, feeder and service load calculations, and Article 625 covers electric vehicle charging equipment. Your engineer confirms how load management is treated in the calculation for your building.
When a panel or service upgrade is still needed
- Spare capacity is too small to give each car a useful share overnight.
- The panel or switchgear has no room for new breakers.
- You plan other electric loads, such as heat pumps or water heating, that need the same headroom.
- You want full-power charging at many spaces at once.
Utility make-ready
If the service, meter or transformer has to change, your utility (for example PG&E, SCE, SDG&E, LADWP or SMUD) runs its own review and schedule. That work often sets the project timeline, which is why capacity is checked first.
Worked examples
Illustration only, not a design. The spare-capacity figures below are assumptions. A load calculation gives your building's real figures.
| Assumption or result | 20-unit garden building | 100-unit podium building |
|---|---|---|
| Assumed spare capacity at 208 V | 80 A | 200 A |
| Level 2 chargers set to 32 A (32 × 1.25 = 40 A each), no load management | 2 chargers (80 ÷ 40) | 5 chargers (200 ÷ 40) |
| Load-managed group limit (spare ÷ 1.25) | 64 A (64 × 1.25 = 80) | 160 A (160 × 1.25 = 200) |
| Ports on that limit | 8 ports | 24 ports |
| Share per car if every port is charging | 8 A (64 ÷ 8) | About 6.7 A (160 ÷ 24) |
In both cases, fewer cars charge at once in practice, so each usually gets more than the worst-case share. If even the worst case is too low for your residents' needs, that's the point to look at a service upgrade.
Apartment owner? See EV charging for apartments. HOA board? See condo and HOA EV charging. Budgeting? See cost and ROI.