The chargers are rarely the expensive part of a project. The service upgrade is. Here is how service limits, demand charges and the electrical code shape a charging project, and how sharing capacity in real time lets a site install the ports it needs.
Dynamic load management is how a site puts more EV chargers on an electrical service than that service could run at full power all at once. It works because chargers rarely all draw full current at the same moment, and because a car that has finished charging does not need the capacity it was given.
For businesses, multifamily buildings, workplaces, fleets and hotels, this post covers why service capacity is the real limit, what an upgrade involves, how demand charges change the math, static versus dynamic control, and how eMÖTEN Power, the dynamic load management layer in eMÖTEN CMS, does it. It is general information, not engineering or legal advice; your electrician and local inspector make the final call.
The electrical code treats EV charging equipment as a continuous load, and the overcurrent protection for each charger must be at least 125 percent of its current rating. A charger rated at 48 A therefore needs a 60 A circuit. Add ten of them without any control and the calculation assumes all ten draw 48 A at once, which is 480 A of continuous load before the building's own lights, HVAC and elevators are counted.
That worst case rarely happens, but a conventional load calculation must plan for it, and on most existing buildings the panel, service or transformer cannot carry it. The project stalls on an upgrade.
A service upgrade can mean a larger panel or switchgear on your side, new service conductors, and often a larger utility transformer. The utility sets the cost and the timeline for its part of the work, and the queue for a new transformer can be the longest item in the whole project.
Before anyone prices an upgrade, find out how much headroom the service actually has. NEC 220.87 lets an electrician base the existing load on actual maximum demand: a year of utility demand data where it is available, or a continuous recording of at least 30 days where it is not. The measured peak is counted at 125 percent, and the new load is added to that. Measured demand can show more headroom than a calculation from panel labels, and the site assessment checklist walks through collecting the numbers.
Capacity is one cost; the monthly bill is another. Many commercial tariffs include a demand charge, typically calculated on the highest average power over a 15-minute period in the billing cycle, as Idaho National Laboratory explains. A few chargers starting together can set a peak that is billed for the whole month.
Load management does not change your tariff, but a site limit caps the charging load the meter can see. A capped peak is a predictable demand charge. See our glossary entry on demand charges for the short version.
Both keep charging inside a limit. The difference is whether the limit adapts to what is happening on site.
| Approach | How it works | Trade-off |
|---|---|---|
| Static setting | Each charger's maximum current is fixed at install, using its adjustable setting | Safe and simple, but every car is held to the low setting even when the site is empty |
| Load switching | Chargers are switched off or queued when total demand passes a set limit | Some cars wait while others charge at full power |
| Dynamic load management | Available capacity is measured or tracked and shared among the chargers in real time | Needs networked chargers and validated control, but uses every amp the circuit can give |
Static settings suit a single charger on a tight circuit. With several chargers and staggered arrivals, a fixed split wastes capacity: a car plugging in alone at 7 a.m. gets the same low current it would on a full lot.
Load management can protect two different things, and the choice sets the hardware you need.
Several chargers share one dedicated branch circuit or feeder with a known rating. The 2023 NEC permits one branch circuit to supply more than one charger when an energy management system manages the load. The control system needs to know the circuit's rating and which chargers sit on it, and it keeps their combined current inside that budget.
Chargers share the building's main service with everything else. Here the system reads a meter on the main and gives the chargers whatever the building is not using at that moment. The chargers back off automatically when the building load rises.
Section numbers below are from the 2023 NEC, which many jurisdictions still enforce. Later editions renumber some of these sections, so check which edition your jurisdiction has adopted and confirm the references with your electrician.
Canada: the Canadian Electrical Code covers electric vehicle energy management systems (EVEMS) under Rule 8-500, and Rule 8-106 sets out when the demand an EVEMS permits can be used in the calculation. CSA C22.2 No. 343, a product standard for EVEMS, was published in 2025. Provincial authorities interpret the rules, so check bulletins from your provincial safety regulator and your utility.
eMÖTEN Power shares each circuit in real time between the chargers actually drawing current, so you can install the charge points the site needs instead of upgrading the supply. It manages chargers over standard OCPP smart charging, the same way on Level 2 and DC.
Shared capacity protects the circuit feeding the chargers, using the ceiling set from your panel schedule. It needs no extra hardware and is included on every plan, and the limit is stored on each charger, so a site keeps its ceiling even if the building's internet drops. Live building metering protects the whole electrical service by reading a meter on the main continuously. It needs one metering device at the panel, quoted with your site.
If data from a charger goes stale, the limit is held. A maximum limit stored on the charger keeps it bounded if it loses contact with the network, and a hardware ceiling in the charger's own configuration is honoured with no management system involved at all. Off-peak charging can be scheduled with a staggered start across the site, so twenty vehicles do not all begin at the same minute, and site owners can lower their site limit from their own login, but never above the safety limit set at commissioning.
eMÖTEN Power also measures the building, telling a failing charger apart from a supply that was never adequate, from recorded data, before anyone is dispatched to site. More detail is on the eMÖTEN CMS page.
Take a parking garage with a 100 A feeder dedicated to charging. Because the setpoint counts as a continuous load, the electrician sets the charging budget at 80 A. The site wants eight Level 2 chargers rated at 48 A. These figures are illustrative; your electrician sets the real ones.
On a 240 V circuit, 10 A is about 2.4 kW, or roughly 24 kWh over a 10-hour overnight stay. Our workplace sizing post estimates about 12 kWh for a 40-mile commute, so even the busiest night covers a typical day of driving. For residents and billing, see the multifamily post.
Load management shares capacity; it does not create it. If the energy your vehicles need each day is more than the service can deliver during their dwell time, you need more supply. That is most often the case with DC fast charging, where one charger can ask for more than a small service can give. For those sites, XEYAR battery-buffered clusters draw steady average power from the grid and cover the peaks from an on-site battery, as our XEYAR post explains. On those sites, eMÖTEN Power still manages the chargers, while the battery is run by its own battery management system (BMS).
It is a control system that tracks how much current a circuit or a whole electrical service can supply and shares that capacity among the chargers in real time, so more chargers can run on the same service without exceeding its rating.
Yes, where the system and its settings meet the code. The 2023 NEC lets the maximum load permitted by an energy management system be used for service and feeder sizing, and the Canadian Electrical Code covers EV energy management systems under Rule 8-500. Your electrician and local inspector confirm the details.
Only when the site is at its limit, which is the alternative to not being able to install the charger at all. When capacity frees up, the chargers that are still drawing current get it back at the next reassessment, within 60 seconds.
For shared capacity on a dedicated circuit, nothing beyond the chargers and your circuit layout, recorded once at commissioning. For live metering of a whole building, one metering device at the panel, quoted with your site.
Send your panel schedule, service rating and how many ports you want. We will tell you whether eMÖTEN Power can fit them on the service you have, which mode suits the site, and when battery buffering is the better answer.