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Use this article if you:
- are quoting charging stations for a building that already exists
- have been told there is not enough power for the number of stations asked for
- have a car park that falls under the January 2027 requirement
The number of sockets is a wiring question. The number that decides whether drivers complain is how many cars can draw current at the same moment, and that is the spare current per phase divided by the six amps a car needs to keep charging. Sockets can outnumber it, because cars stay parked far longer than they charge.
None of that is readable from the drawings. It comes from what the building already draws, and the supplier already holds that figure.
If you are pricing a job this week, a 30-day free trial of ELVO lets you set one shared current limit across stations and see the behaviour before you commit to a design.
What actually limits the number of charging stations
Three numbers get mixed up on every job: how many points the rules require, how many sockets the wiring carries, and how many cars can draw current at once. The third decides whether drivers complain, and it is the one nobody measures.
| What people size on | What actually decides it | How you check |
|---|---|---|
| The number of parking spaces | Regulation sets a minimum number of points, never a maximum. Power sets the maximum | Read the requirement for the building type, then size against the supply |
| The rating of the main protective device | The lower of that rating and the capacity agreed in the supply contract, minus what the building already draws | Interval data from the electricity supplier, or a logger at the board |
| The nameplate power of each station | What each car draws once a shared limit is applied, which is far less | Currents per phase under that limit, not a sum of nameplate ratings |
| The number of sockets | How long cars stay parked, which decides how many of them can share one charging point | Compare parking time against the energy each driver needs |
| Total current available | Current per phase, because a single phase station loads one phase on its own | Ask which phase each station is wired to |
The requirement side, as of August 2026, comes from the buildings directive, which obliges member states rather than building owners directly, so the wording that binds a specific site is the national law that carries it. New and majorly renovated non-residential buildings with more than five parking spaces are to get at least one recharging point per five spaces, and offices one per two. All non-residential buildings with more than 20 parking spaces, not only new ones, are to get at least one point per ten spaces by 1 January 2027, or ducting for half the spaces, though member states may defer that to 1 January 2029 for buildings renovated in the two years before 28 May 2024 in order to meet the earlier requirements. The same article requires the pre-cabling to be dimensioned for simultaneous and efficient use, and, where appropriate and as far as technically and economically feasible, to support installing a load or recharging management system.
How to work out the number, step by step
The first two steps decide everything after them, and they are the ones usually skipped, which is how a quote ends up carrying a grid connection request nobody needed. The later steps are what keeps the installation standing on the day a measurement or a connection is lost.
- Ask the electricity supplier for the building’s interval data before you measure anything. They already hold months of it, it costs nothing, and it covers seasons a logger will miss. Only when they will not release it should you put a logger on the main board, and then remember that a week in a mild month is not the annual peak.
- Work out the spare current at the main board, then set the working limit below it. Take the lower of two numbers, the rating of the main protective device and the capacity agreed in the supply contract, then subtract the measured peak and a margin for the building’s own growth, in amps per phase. The figure you configure sits a few amps under that, because meter readings are averaged over the metering interval and short peaks hide inside them. Ask what exceeding the agreed capacity costs. Then follow the chain down, because these numbers nest: the supply feeds boards, the boards feed circuits, the circuits feed the chargers, each rated separately, and the one that binds is the tightest rating above the stations rather than the figure on the main board.
- Work out two numbers, not one. The spare current per phase divided by six amps is the ceiling on cars charging at the same moment: three phase stations take their six amps on all three phases, so 60 spare amps per phase holds ten of them, while single phase stations take theirs on one phase, so the same 60 amps holds ten per phase if they are spread evenly. That ceiling is the worst case rather than a target: ten cars at six amps is ten cars charging slowly. The number of sockets is the other question, and it is usually larger: at six amps on a single phase a car draws about 1.4 kW, so ten hours delivers roughly 14 kWh, while 50 km at 18 kWh per 100 km needs about 9 kWh. Those figures are an illustration, not a claim about your fleet, and winter is worse.
- Decide what happens when the current runs out. What is left is not divided further once each car is down to six amps per phase, because below that the station cannot signal a lower current and the car stops instead of slowing. Sessions queue instead: some hold while others finish, and a priority rule decides who waits, which is how the van leaving at six goes ahead of the car leaving at five. Agree that rule with the client in advance.
- Decide whether the stations follow the building, and what happens if that measurement is lost. If the chargers share the supply and you want them to use whatever the rest of the building is not using, that needs a meter or a current clamp on the main supply, read several times a minute. It also needs a figure to fall back on when that reading is lost, agreed in advance, and the shape of that figure matters: a safe total for the board, shared between the cars charging on it, rather than a number set on each charger. Four cars sharing a 24 A fallback take six amps each and keep charging. The same 24 A written on each of the four chargers is 96 A on a board that cannot carry it.
- Decide what the stations do when they lose the platform. This is the other connection, and it behaves differently: a limit already set on a station stays in force when the link to the software drops, for the session in progress and for the ones after it. The case to avoid is a station carrying no limit at all, because that one charges at whatever its hardware allows. Set the standing limit first, and let schedules and per session limits sit on top of it.
- Check how single phase stations are spread across the phases. Three single phase stations all wired to the first phase use up the same headroom on the phase that limits you as nine spread evenly, while delivering a third of the charging. Uneven single phase load also runs through the neutral, so ask the distribution system operator (DSO) what imbalance they accept. The fix belongs in the drawing: rotate the phase from one charger to the next, and record which phase each one sits on, though some newer stations move between phases on their own.
- Ask for a bigger connection only if the number still does not work. Distribution system operators are required to cooperate on a non-discriminatory basis with any undertaking that owns or operates recharging points, private ones included. That does not oblige anyone to grant a reinforcement, but the request cannot be brushed aside. Ask for the date as well as the price.
The wiring is the electrician’s responsibility and has to be certified by someone authorised to do it, so bring that person into the decision on the limit.
The four levels of load management
Load management is not one thing, and a quote rarely says which level it includes. There are four, each with its own hardware and its own answer to how many cars the building carries at once. The step from the second to the third costs nothing and is the one most often skipped.
No management at all. Every station can draw its nameplate current, and the sum of the nameplates passes the connection. It works until enough cars arrive together, and then protection somewhere back up the line opens.
A fixed share per station. Each station is capped at a lower current, whether the others are charging or not. It needs no measurement, and it wastes whatever nobody is using: one car alone at three in the morning still gets a quarter of the supply.
One limit for a group of stations, shared between the cars actually charging. Same wiring and same total as above, except that a car which finishes hands its share back to the ones still plugged in. All it needs is a platform above the stations that can send each of them a limit, and it is where most car parks belong.
Dynamic against the building’s own consumption. A meter or a current clamp on the main supply reads everything the building draws, lifts and ventilation and lighting included, and a controller gives the stations the difference between that and the limit it holds. This is the level that lets a car park use the building’s night, and the level that needs the extra hardware and its wiring.
None of the four creates power, and two things follow. Extra sockets are carved out of the same spare current. And a building already at its limit at six in the evening has nothing to give then, which is a scheduling problem rather than a cabling one.
Q: Can I put twenty sockets on a supply that only carries ten cars at once? A: Yes on a site where cars park overnight or for a full working day, no on a site where everyone arrives and leaves together.
What this looks like on a real job
A smaller installer could not bid on a tender from a large client because they had no software platform to offer. Software was a contract requirement, and load balancing was among the functions the client needed. The client also had chargers from another vendor installed, and wanted those on the new platform too.
With a platform behind them, the installer could show the client every function on the list, load balancing included. They bid, they won, and they delivered the project, with the other vendor’s chargers brought on too.
What ELVO does about load
A group in ELVO is a set of stations that share one limit in amps, the figure you set. The platform works out each active connector’s share from that limit and the sessions running, and it keeps redoing that as cars come and go, so a car that finishes hands its share to the ones still charging.
If the chargers have a supply of their own, one group carrying that connection’s limit is the whole setup. If they share the building’s supply, the number on the group is the spare current you measured, and you have two ways to use it. You can leave one number there, sized for the building’s busiest hour, and it holds around the clock. Or you can put a weekly schedule on the group, with a different limit per day and time slot, in amps or watts, if you want more current available at night than that one number allows. Where the chargers are to follow the building’s own consumption minute by minute, that reading comes from a meter or a current clamp on the main supply, which belongs in the electrical design, and the group limit still applies above it.
If the car park is fed from more than one board, one group per board, each carrying its own number, keeps every cable inside its own limit, and no group borrows from another. Where single phase stations sit on different phases, a group per phase keeps each phase inside the current it has to give.
When a driver says charging is slow, you can ask a station what schedule it is applying to that connector at that moment and read the answer in the platform. What the car gets is the lowest of four things: its share of the group, any schedule on top of that, the maximum set on the station itself, and what the car will accept. Where a station’s firmware exposes its own maximum, ELVO sets that from the platform too, anywhere between 6 and 64 A. And a limit already sent stays on the station if the link to the platform drops.
ELVO is compatible with more than 700 station models and holds an Open Charge Alliance certificate, Full and Security. An account opens by self-service, so you can put two stations in a group and watch the split the same day, and EPBD Article 14 load management is in the self-service plan rather than a paid module.
Q: Do the stations have to be the same brand to share one limit? A: No. The limit travels as a charging profile over OCPP, which every compliant station understands, whoever built it.
Frequently asked questions
How many EV chargers can a building support? As many sockets as the wiring carries. What is limited is how many cars can draw current at the same moment, and that is the spare current per phase divided by the six amps a car needs to keep charging. Sockets can outnumber that, because cars sit parked far longer than they charge.
What is the difference between static and dynamic load management? Static gives each station a fixed share of the current, used or not. Dynamic measures what the whole building is drawing, on a meter at the main supply, and gives the stations what is left at that moment. In between sits one limit for a group of stations, shared out between the cars actually charging.
Do I need a new grid connection to install EV chargers? You do not know until the building is measured, and the measurement is usually cheaper than the assumption. Ask the electricity supplier for the interval data they already hold, compare the peak against the capacity in the supply contract, and work out how many cars the gap covers before requesting anything.
What happens if too many cars charge at once? The stations share what there is and cars charge more slowly, down to six amps per phase. Below that a car stops rather than slows, so the current is not divided further. Sessions queue instead, and the priority rule decides who waits while the others finish.
What happens if the chargers lose their connection? There are two connections and two answers. If the link to the platform drops, the limits already set on the stations stay in force. If the meter reading the building is lost, the system falls back to the current it was configured with in advance. The case to avoid is a station carrying no limit at all.
Does the EPBD require load management? It requires the conditions. The directive says pre-cabling and ducting must be dimensioned for simultaneous and efficient use of the required recharging points and, where appropriate and as far as technically and economically feasible, must support installing a load or recharging management system.
Read next
- EPBD Article 14: what the directive requires from charge management software
- How to check OCPP 1.6 charger compatibility before you buy
- OCPP backend: what it is and how to choose one
- EV charging management software: what it is and who needs it
Sources
- European Union, Directive (EU) 2024/1275 on the energy performance of buildings, Article 14
- European Union, Directive (EU) 2019/944 on the internal market for electricity, Article 33
- Open Charge Alliance, Open Charge Point Protocol
- Open Charge Alliance, ELVO Technology participant page
Bottom line
The number you can defend in front of a client comes out of what the building already draws, and out of which of the four levels the quote includes. Everything else is arithmetic on top of those two.
Try ELVO free for 30 days. The fastest way to test this is to put two stations in a group, set the limit, and watch what each one does.
ELVO Team. We operate CPMS for manufacturers, distributors, installers, and operators across Europe and beyond.
Published 20 August 2026.