Resources · Guide
G100 import limitation lets an EV charging site draw more power than its raw connection would otherwise allow - safely, and often without a costly grid upgrade. This is what the recommendation asks for and how a charger has to behave to satisfy it.
What it is
G100 is an Engineering Recommendation from the UK Energy Networks Association (ENA). It sets out how large loads and microgeneration - solar PV, home and site batteries, and EV chargers - can be actively limited so they never draw more from, or export more to, the grid than the network can safely accommodate.
For EV charging the important half is import limitation: a control scheme that holds the power a site imports within an agreed capacity, adjusting charging in real time to stay inside it. Under G100 Issue 2 both import and export limitation are covered, built around Customer Limitation Schemes agreed with the Distribution Network Operator (DNO).
A site's raw connection is often smaller than the peak an EV charging installation would draw. Without limitation the DNO may demand an expensive, slow grid reinforcement before granting a connection. A G100 import-limitation scheme lets you commission more charging on the existing supply - the site simply promises, and provably enforces, that it will not exceed its agreed import capacity.
Who this is for
This reference is written for CTOs and technical decision-makers, charge point manufacturers designing G100-ready hardware, and charge point operators (CPOs) who have to keep live sites compliant as they scale.
How import limitation works
Every G100 import-limitation scheme has the same skeleton: a place where demand is measured, a controller that decides how much charging the site can afford right now, and a small set of load states the scheme moves between as demand rises and falls.
The measurement point
Limitation is enforced against a measurement taken at the site boundary, where total import is visible - not at an individual charger. The scheme continuously reads that point so charging is throttled against real, whole-site demand, including everything else drawing power behind the same connection.
The control scheme
A controller compares measured import against the agreed capacity and modulates charge current to keep the site inside it. One or many chargers can run under a single Customer Limitation Scheme, sharing the available headroom rather than each assuming it has the whole connection to itself.
CLS
Normal running. Site import sits at or below the agreed continuous capacity and charging is delivered at the fastest rate the remaining headroom allows. The scheme monitors the measurement point continuously so it can react before the limit is reached.
ELS
A short, bounded excursion above the continuous limit is tolerated only for a defined window before the scheme must act. It is a transitional state, not a licence to run above capacity - the controller has to detect the excursion and begin reducing import promptly.
MEL
The absolute ceiling set by the Distribution Network Operator, the hard boundary the installation must never cross. As the load approaches it the control scheme curtails charging back into the continuous state, and for bidirectional (V2G) sites it also caps how much power can flow back to the grid.
Fail-safe
The failure mode. If the scheme cannot measure the site, cannot control the load, or an excursion is not corrected within the permitted window, it must fail safe and stop charging rather than keep drawing power it can no longer prove is within limits. Losing the measurement signal has to be treated as an excursion, not as an all-clear.
The scheme lives in the Continuous Load State almost all of the time. A surge in site demand can push it briefly into the Extended Load State, from which it must detect the excursion and reduce import back into continuous running before the Maximum Export Limit is threatened. The transitions matter as much as the states: a compliant charger is defined by how quickly and reliably it moves back down, not just by the limits themselves.
What it means for a charger
Meeting G100 is less about a single feature and more about how the charger behaves under load and under fault. Four requirements shape the design.
Charge current is adjusted in real time against a live measurement of site demand, so EV charging soaks up spare capacity without ever pushing the connection past its agreed limit. Multiple chargers coordinate as one scheme rather than competing for headroom.
If the measurement feed, a meter or a communications link fails, the charger must fall back to a conservative default rather than assume full capacity is available. Fault detection on the measurement devices is part of staying compliant, not an optional extra.
The scheme has to detect an excursion and pull import back to the agreed capacity within a short, defined window - on the order of seconds, not minutes. Sizing the control loop and the actuation path to hit that response time is a core design constraint.
Limit settings are protected against unauthorised change through passwords, PINs or physically sealable access, and the equipment is type-tested to G100 so the DNO can trust the scheme without re-verifying every installation.
How Versinetic helps
Versinetic's charging module hardware is designed to satisfy G100 out of the box - measuring the site, coordinating chargers and failing safe - so you meet DNO requirements without engineering the control scheme from scratch.
Smart charge point controller
The controller that runs the import-limitation logic on the charger - monitoring the measurement point and modulating charge current in real time to hold the site within its agreed capacity.
Explore MantaRayAC charge controller board
A type-tested AC charge controller with optional voltage calibration for chargers built without their own meter, improving the accuracy of the readings the control scheme depends on.
Explore EELLocal load-balancing controller
Coordinates a group of chargers as a single Customer Limitation Scheme, sharing available headroom across the site so multiple points stay compliant without a bespoke integration each time.
Explore LinkRayWhole-site energy management
Ties chargers into site-wide demand, PV and battery storage so the whole installation respects one import ceiling - the level at which G100 compliance is ultimately judged.
Explore Site load managementGet in touch
Tell us what you're building and our engineers will help you scope the fastest, lowest-risk route to market. A conversation directly with the people who design the charging modules.