UK ENA G100 Issue 2 Export Limitation Compliance Guide

Key Takeaways

• ENA G100 Issue 2 sets technical requirements for export and import limitation schemes for installations after 1 May 2023.
• All generators in Great Britain must have Loss of Mains (LoM) protection, with specific RoCoF settings.
• Distribution Network Operators (DNOs) can charge for connection quotes, with updated costs effective from 1 January 2026.
• Manufacturers are responsible for uploading and maintaining product compliance data on the ENA's Connect Direct platform.

Understanding ENA G100 Issue 2 for Export Limitation

ENA G100 Issue 2 details the technical requirements for customers' export and import limitation schemes. This standard applies to installations after 1 May 2023. It ensures that your solar or other generation system connects to the grid safely and without negatively impacting the network.

The Energy Networks Association (ENA) is the trade association for energy networks in the UK. Its members own and operate the infrastructure that carries electricity and gas. The ENA publishes standards like G100 to guide connections to these networks.

What is actually going on: Grid Connection Standards

Connecting any generation equipment, such as solar panels or wind turbines, to the electricity distribution network in Great Britain requires compliance with specific engineering recommendations. These standards ensure the stability and safety of the grid.

The primary standards for connecting generators in parallel with public low voltage networks are G98 and G99. These superseded the previous ENA standard G59 on 17 May 2019. G98 applies to smaller, micro-generation connections (16 amps or less per phase), while G99 covers larger generation equipment. G100 specifically addresses schemes that limit the amount of electricity you can export or import from the grid.

Distribution Network Operators (DNOs), such as Electricity North West, manage these connections. They offer various connection types, including:

• Generation and Storage: For solar panels, wind turbines, and energy storage, from domestic to industrial scale.
• G98 Micro-Generation and Storage: For connecting generation, including energy storage, at 16 amps or less per phase.
• Generation G99: For connecting generation equipment to distribution networks, a legal requirement for certain generators connecting on or after 27 April 2019.

Flexible Connections and Export Limitation

To manage electricity demand across the network, DNOs may offer "flexible connections." These can lead to quicker connection dates and potentially cheaper quotes by avoiding or deferring network reinforcement. An "Export Limited Connection" allows you to install more generation capacity than you are allowed to export, with your export to the network capped at an agreed level.

Another flexible option is "Active Network Management (ANM)," a smart control system that automatically adjusts your import or export in real time based on available network capacity.

Loss of Mains Protection: A Mandatory Requirement

All generators connected to the distribution networks in Great Britain must have Loss of Mains (LoM) protection. This is one of many protection requirements on the electricity system. LoM protection checks if a generator is still connected to the supply network. This applies to generating plants running in long-term parallel with the distribution network and within the scope of Engineering Recommendation (EREC) G59, regardless of the generator type.

The requirements for LoM protection have been updated. Where LoM is provided by vector shift, it must be removed and/or replaced with Rate of Change of Frequency (RoCoF). The RoCoF setting requirement has changed to 1Hz/s with a definite time delay of 500 milliseconds. The date for compliance with these updated EREC requirements was 1 September 2022.

DNOs will contact non-compliant generator owners. If no evidence of compliance is provided, de-energisation of the generation site's Connection Point may occur after 26 weeks. Compliance makes generation more reliable, less likely to trip off, and ensures more consistent generation.

What you can check yourself, and what you cannot

As a homeowner or system owner, you can check that your installer has provided documentation confirming your system's compliance with ENA standards, including G100 and LoM protection. You can also verify that your equipment is listed on the ENA's Connect Direct platform.

You cannot, however, change grid-protection settings yourself. Grid-protection settings are set by an accredited installer. Changing them can breach your connection agreement and compromise grid safety. For any technical adjustments or updates to your LoM protection, you must engage a qualified and accredited installer.

Equipment Compliance Status

The ENA hosts manufacturers' data and their statements of compliance for devices covered by standards like G98, G99, and G100. This data is now available on Connect Direct, which replaced the Type Test Register (TTR) on 16 April 2024. Manufacturers are responsible for uploading and maintaining this data.

Compliance statuses include:

• Compliant: Device and documentation reviewed and deemed compliant. This is indicative only, and DNOs retain the right to review suitability.
• Compliant — on-site confirmation by DNO Required: Compliance depends on on-site confirmation by the DNO and may involve site-specific technical factors.
• Further Information Required: More information is needed from the manufacturer before a 'compliant' status can be achieved.
• Non-compliant: Device and documentation cannot be deemed compliant at this stage.
• Non-compliant for new installations: This status applies to devices previously compliant but no longer meeting updated standards, such as the Limited Frequency Sensitivity Mode - Overfrequency (LFSM-O) requirements from 1 September 2022.

Connection Offer Expenses: What you might pay

Under the Electricity (Connection Offer Expenses) Regulations 2018, DNOs are permitted to charge customers for their 'connection offer expenses,' whether the offers are accepted or declined. These charges help DNOs recover costs incurred when producing quotes, ensuring a fairer allocation of costs.

The charges cover expenses such as:

• Assessment of network impacts.
• Undertaking surveys and site visits.
• Designing the connection.
• Accommodation.
• Preparing the quote.

Updated costs for these services are effective from 1 January 2026. If you receive an invoice for a connection quote, you will have 30 days to pay it, or the connection offer will become invalid. If the charge is not paid within 30 days, you remain liable for the charge. Repeated non-payment (e.g., for three quotes) may result in a requirement for advance payment for any further quotes.

Domestic customers applying for connections for up to and including four domestic properties are exempt from these quote charges. DNOs will not charge for budget estimates, minor connections (1-4 properties), cancellations within a cooling-off period, or offers for service alterations or diversions. However, charges apply for Extra High Voltage offers, High Voltage offers over 1MW/1MVA, requotes, cancellations after the cooling-off period, and Gen+ initial assessments.

What the published sources do not tell you

Statutory and engineering documentation provides a high-level overview of ENA G100 Issue 2 and related connection requirements. However, it does not provide specific technical details of the G100 standard beyond its applicability date. It also does not include detailed application forms or processes for G98, G99, or G100 connections.

The exact "curtailment index" or specific export/import caps for flexible connections are not detailed, as these vary by DNO and site-specific conditions. The full list of recognized contractors for LoM protection updates is also not provided. For these specific details, you would need to consult the full ENA G100 document, your specific DNO's connection guides, or an accredited installer.