GUIDE · FOR UK SOLAR INSTALLERS · 7 MIN READ
G100 Export Limitation: An Installer's Guide
The short answer
EREC G100 is the Energy Networks Association standard for schemes that cap what a site exports to the grid, or imports from it. A G100 scheme measures power where the site meets the network and turns generation or storage down, or raises demand, so export never goes over the figure the DNO agreed. It must fail safe and its settings are locked. You apply for it with the G98 or G99 application, and it is how the SGI-2 and SGI-3 fast tracks keep export to 16A or 32A.
Every rule and figure below comes from the ENA and DNO sources listed at the end, checked on 16 October 2026.
What G100 is
Engineering Recommendation G100 is the ENA document on Customer Export and Import Limitation Schemes. The ENA's Distributed Generation Connection Guide (March 2025) says "Export and import limiting schemes need to be compliant with EREC G100", and describes the devices as letting "a limit to be set above which the generation will not export / a demand customer will not be able to import."
G100 sits alongside G98 and G99 rather than replacing them: NGED says the generation and storage behind a scheme must still meet G98 or G99 as applicable. NGED's current guidance refers to EREC G100 Issue 2 Amendment 2.
When you'd use export limitation
- Instead of reinforcement. NGED says customers who want more generation or storage but face costly or slow upstream reinforcement can restrict the net export of their connection instead.
- On the small-installation fast track. SGI-2 and SGI-3 may need a G100 scheme holding export to 16A or 32A (table below).
- By choice. The ENA guide notes a customer can ask for a restricted connection such as a maximum export level.
It is not the same as a curtailable connection. Since 1 April 2023 DNOs must consider offering curtailable connections, where export can be restricted at certain times until reinforcement is finished, with compensation above an agreed limit (ENA guide). A G100 cap is permanent unless the DNO agrees to change it.
How a G100 scheme works
NGED describes a scheme that measures apparent power at the installation's exit point and then restricts generation or storage output, or increases the site's demand, so the agreed export capacity is never exceeded. The same scheme can limit import, by raising or lowering demand so the maximum import capacity is not exceeded. NGED also says connections at high voltage and above need a reverse power flow relay.
Fail-safe rules, response times and locked settings
- Response time. NGED's customer export limitation scheme guidance, written to G100 Issue 2 Amendment 2, says the scheme must bring current back within the limit "typically within 15s with a maximum reaction time of 60s". NGED's older export limitation page still says within 5 seconds, so check which figure your DNO applies.
- Fail-safe. If any component or signalling link fails or loses power, the scheme must still bring export down to the agreed capacity in the same time.
- Locked settings. After commissioning the customer cannot change the settings. They must be protected by a password, PIN or a sealable enclosure, and changed only with the DNO's written agreement.
What "G100 compliant" means
It means the scheme meets EREC G100. Two things to check before you specify a device:
- It is listed. NGED says the ENA's Connect Direct database lists compliant G100 devices.
- It is Fully Type Tested, for small installations. The ENA guide says G100 schemes used on G99's small-installation procedures did not used to need Fully Type Testing, but after revisions to G99 they now do.
G100 on the G99 fast track
SSEN's fast track (Small Generation Installation, SGI) categories show where a G100 scheme comes in. SSEN aims to respond within 10 working days.
| Route | Unit design capacity | Registered capacity | Total registered | G100 export limit | Form |
|---|---|---|---|---|---|
| SGI-1 | 32A (7.36kW) or less | 16A (3.68kW) or less | 16A (3.68kW) or less | Not required: the limit is factory-set on the inverter | A3-3 |
| SGI-2 | 32A (7.36kW) or less | 16A (3.68kW) or less | 32A (7.36kW) or less | May be required, limiting export to 16A (3.68kW) | A1-2 |
| SGI-3 | 32A (7.36kW) or less | 32A (7.36kW) or less | 60A (14.72kW) or less | May be required, limiting export to 32A (7.36kW) | A1-2 |
Above these limits the job is a standard G99 application, with the G100 scheme applied for alongside it. Our G99 route checker works out which side of the line a job falls.
kW to amps
DNOs write limits in amps per phase. Enter the export cap in kW to see it both ways, at 230V.
Single-phase supply
16.0A
Three-phase supply, per phase
5.3A
For reference: 16A is 3.68kW and 32A is 7.36kW on a single phase. The agreed figure is always the DNO's.
How to apply: the forms
The scheme is applied for with the generation, not on its own. How two DNOs set it out:
| Stage | NGED | SSEN fast track |
|---|---|---|
| Applying | Form A (CLS application), sent with the generation, storage or new connection application. Online, tick that a CLS is included. | Form A1-2 on the fast track, with a G100 declaration and the inverter's G98 type test certificate. |
| Installing | Only once NGED has approved the connection. NGED may witness some commissioning tests. | Commission within 3 months of SSEN's confirmation. |
| After commissioning | Form C (installation and commissioning) within 28 days. | Form A3-2 within 28 days. |
Other DNOs use their own versions of the forms. Find yours, and how it takes applications, with the MPAN lookup in our DNO application guide.
Export limits that aren't G100
A manufacturer can limit a generating unit's Registered Capacity below what it could naturally produce. The ENA guide says these limits are semi-permanent, set by the manufacturer only and never by the generator, and must not be possible to change or defeat without the Registered Capacity being redeclared; the restriction is agreed with the DNO. That is how SGI-1 works: SSEN says no G100 scheme is needed there because the limit is factory-set on the inverter. A G100 scheme, by contrast, caps the whole site at the connection point.
G100 on commercial jobs
Commercial roofs are usually standard G99 jobs, and an export cap is often what gets one connected without a reinforcement bill. A site that uses most of what it generates in the day loses little by capping export, so raise it at the site survey and with the DNO early, before the customer is quoted on full export.
Once you can take on bigger connections, the bottleneck is usually finding the work. Solar Surveys UK books qualified commercial solar survey appointments with business owners for UK installers, and our guide on how to get commercial solar leads compares the other channels.
G100 export limitation: FAQ
What is G100?
EREC G100 is the Energy Networks Association's engineering recommendation for customer export and import limitation schemes. The ENA's 2025 connection guide says any export or import limiting scheme has to comply with it.
Is G100 export limitation required for solar panels?
Only when export has to be held below what the system can generate. That happens when the DNO offers a capped export instead of reinforcing the network, when the customer chooses a cap, or on the SGI-2 and SGI-3 fast tracks. On SGI-1 SSEN says no G100 scheme is needed because the limit is factory-set on the inverter.
What does G100 compliant mean?
That the scheme meets EREC G100: it measures power at the site's exit point, keeps export under the agreed figure, fails safe if anything breaks, and has its settings locked. NGED says compliant devices are listed on the ENA's Connect Direct database, and the ENA's 2025 guide says G100 devices used on G99's small-installation procedures must now be Fully Type Tested.
How do I apply for G100 export limitation?
With the generation application, not separately. NGED wants its Form A (CLS application) with the G99 or storage application and Form C within 28 days of commissioning. On SSEN's fast track it is Form A1-2 with a G100 declaration, then Form A3-2 within 28 days.
Can the export limit be changed later?
Not by the customer. NGED says settings must be protected by a password, PIN or sealable enclosure and changed only with the DNO's written agreement.
Does G100 apply to batteries?
Yes. NGED's guidance covers generation including energy storage, and a scheme can limit import as well as export, for example by raising or lowering the site's demand.
What is the difference between G99 and G100?
G99 is the connection standard for generation over the G98 limit; G100 covers the scheme that caps what a site exports or imports. A G100 scheme is applied for as part of the G98 or G99 application, and the generation still has to meet G98 or G99.
Sources
Checked 16 Oct 2026. Official documents from the Energy Networks Association and distribution network operators. Where a rule is one DNO's own, the text says so. A plain-English summary, not engineering advice: confirm with the DNO and a competent engineer.
Related guides
- G99 application for commercial solar
Forms, Types, timescales, and a G98 or G99 route checker.
- DNO application for solar
Find your DNO from the MPAN and pick the right route.
- G98 explained: notification, limits and forms
The 16A-per-phase limit and the fit-and-inform route.
- Commercial solar survey checklist
What to check on site, including the supply and export.
Fill your diary with commercial solar surveys
Booked, qualified survey appointments with business owners. Pay per appointment, no retainer, from £400+VAT to £1,000+VAT per lead depending on system size.