What G100 is
National Grid Electricity Distribution (NGED), which runs the network across the Midlands, the South West and South Wales, describes an export limitation scheme as one that "measures the Apparent Power (kilowatts) at the exit point of the installation and then uses this information to either restrict generation/energy storage output or increase the customer demand in order to prevent the Agreed Export Capacity from being exceeded" (NGED: export limitation).
In plain terms: a meter or sensor at your incoming supply watches how much power is leaving the site. If export gets close to the limit agreed with the network operator, the inverters turn down, or a battery or other load soaks up the surplus. The rules for designing and testing these schemes are in G100, published by the Energy Networks Association. The connection itself still goes through G98 or G99.
Why your network operator might suggest one
When the operator assesses a G99 application, it checks whether the local cables and transformers can take the export you have asked for. If they cannot, the offer may include reinforcement works, with a cost and a wait. NGED puts it this way: customers told that more export capacity "will require costly or time bound upstream reinforcement, may choose to restrict the net export of their connection rather than wait for or contribute to the reinforcement" (NGED).
So an export limit is usually a choice you make, not a penalty: a lower export figure in return for a cheaper or quicker connection.
What it means for your site
| Your site | Effect of an export limit |
|---|---|
| Uses most of the solar output on weekdays and weekends (cold stores, food production, care homes) | Little or no generation lost, because little would have been exported anyway |
| Busy on weekdays, closed at weekends (offices, many factories) | Some weekend and holiday generation is turned down, mostly in summer |
| Large roof, small daytime use (some warehouses, farm buildings) | The limit can cut a large share of output; a smaller array or a battery may make more sense |
Your half-hourly meter data shows how much export a limit would actually stop. The survey uses it to compare a full-export design, an export-limited design and a smaller system; see energy data analysis. A battery can store power that would otherwise be curtailed, at extra cost. Our calculator shows how much the share used on site moves the payback.
What the network operator requires
NGED's published requirements for a customer export limitation scheme are a useful guide to what operators expect (NGED):
- The scheme must comply with G100, and the generation and storage with G98 or G99 as applicable.
- It must bring export down to the agreed maximum within 5 seconds.
- It must be fail-safe: if any part of it fails or loses power, export must still be brought down to the agreed maximum within 5 seconds.
- The installer submits an export limitation application form with the generation application.
- Once approved, the equipment can be installed and commissioned; in some cases the operator witnesses the tests.
- The installer sends an installation and commissioning form within 28 days.
Other operators publish their own forms and guidance, so the details differ by area. Your installer handles the paperwork; your part is agreeing the export figure.
How it affects the timeline
| Route | What happens | Effect on timing |
|---|---|---|
| Small system on fast track, export capped by G100 | NGED's G99 fast track covers single installations where a G100 scheme limits export to 16A or 32A, with an answer within 10 working days and up to 3 months to install | Usually the quickest route for small business systems |
| Standard G99 with an export limit | The limit is part of the application; the operator assesses the lower export figure | Can avoid waiting for reinforcement |
| Standard G99 with full export | The operator assesses full export and may require reinforcement | Can add cost and time if the network is constrained |
Fast track details are from NGED's fast track page, checked 3 November 2026. In Northern Ireland, NIE Networks' G99/NI Fast Track covers capacity up to 60 amps per phase with export limited to 16 amps per phase, and its parameters changed on 1 May 2026 (NIE Networks).
Questions to ask your installer
- What export figure are you applying for, and why?
- How much of our generation would a limit turn down, based on our half-hourly data?
- Would a smaller array, or a battery, pay back better than a larger array with a low limit?
- Which network operator covers us, and what are they currently seeing on our part of the network?
- Is the export limitation device type tested, and who is responsible for it after commissioning?
A free survey answers these for your site. See what you qualify for.
Frequently asked questions
What is a G100 export limitation scheme?
A system that measures the power leaving your site and turns down your solar or battery, or raises your demand, so export stays within the figure agreed with the network operator. G100 is the Energy Networks Association's engineering recommendation for how these schemes are designed and tested.
Will an export limit reduce my savings?
Only by the generation it turns down, and that is usually power you would have exported for a few pence rather than used at your full unit rate. A site that uses most of its solar output on site loses little. A site that is empty at weekends loses more in summer. Half-hourly data shows the figure.
How fast must an export limitation scheme act?
NGED's requirements say the scheme must bring export down to the agreed maximum within 5 seconds, and must be fail-safe, so that if any part of it fails or loses power, export is still brought down within 5 seconds.
Can an export limit speed up my grid connection?
It can. If the network cannot take full export without reinforcement, asking for a lower export figure may avoid the works and the wait. NGED says customers may choose to restrict net export rather than wait for or contribute to reinforcement.
What paperwork does an export limitation scheme need?
At NGED, the installer sends an export limitation application form with the generation application, installs and commissions the equipment once approved, and sends an installation and commissioning form within 28 days. The operator may witness some tests. Other operators have their own forms, and your installer normally handles them.
Related pages
- G99 and DNO applicationsG98 versus G99, what goes into a DNO application, connection offers, export limitation under G100, reinforcement costs and how the survey checks your supply.
- G98 vs G99The difference between G98 and G99, the fast track in between, and what each means for your project timeline and paperwork.
Battery storageWhen a commercial battery pays: storing surplus solar, time of use tariffs, peak shaving, sizing from half-hourly data, illustrative costs, safety and siting.- Energy data analysisHow half-hourly consumption data shapes solar sizing and payback: getting the data, profile classes, baseload, weekend and seasonal use, self-consumption and batteries.
- Feasibility studyWhat a solar feasibility study covers, desktop versus on-site assessment, and the outputs a decision maker needs: size, yield, savings, payback, grid and risks.