MCS, grants and export
What Is G100 and Why Does It Matter for UK Home Batteries?
Most homeowners who have done their homework on grid connection know about G98 and G99, which govern how solar panels notify the distribution network. G100 is the newer engineering recommendation that specifically covers battery storage systems with grid export capability. If your battery can send electricity to the grid, this one applies to your installation.
Helpful video reference. Upvolt Energy's "Upvolt and G100: Making UK solar and storage truly grid-ready" has Upvolt co-founder and CEO Alex explaining UK grid constraints, the role of DNOs, and what G100 means in practice for homes with battery storage. Upvolt Energy is a UK MCS-certified solar, battery storage, and smart energy installer.
Grid export from a battery is notifiable work
Connecting a battery storage system for grid export without the correct DNO notification is a breach of your grid connection obligations. DNO notification must be submitted and, where required, approved before the system is energised for export. This applies whether your battery charges from solar, from the grid overnight, or both. Your MCS-certified installer is responsible for determining which notification applies and submitting it before commissioning.
1. What G98 and G99 were designed for
G98 and G99 are the engineering recommendations that govern how small generators connect to the UK's low-voltage distribution network. G98 applies to micro-generators up to 16A per phase with no battery export: in practice, this covers most domestic solar-only systems under around 3.68 kW per phase. G99 covers larger or more complex installations.
Both recommendations were written primarily with generation in mind: solar panels, micro-wind, micro-hydro. They set out requirements for protection settings, anti-islanding behaviour, and the process for notifying your distribution network operator (DNO) before you connect and start exporting. They do a good job for what they were designed to cover, but battery storage that independently controls its own export introduces different considerations that G98 and G99 were not written to address.
2. What G100 adds for battery storage
G100 is the Energy Networks Association (ENA) engineering recommendation specifically for Battery Energy Storage Systems (BESS) connecting to the low-voltage distribution network. Where G98 and G99 deal with generation, G100 deals with storage: systems that can receive power from the grid, hold it, and export it later, independently of whether there is any associated solar generation.
The recommendation sets out requirements for protection settings, communication protocols, and crucially, the ability for the DNO to instruct the system to curtail or cease exporting when the local network is under stress. This last point matters because a battery that can export at any time of day (rather than only when the sun is shining) puts different and less predictable demands on the local network than a solar-only system does.
Why DNOs care about battery export
Solar panels only export during daylight hours and their output roughly tracks local demand patterns. A battery can export at any time, including evening peaks when the network is already under load. G100 gives DNOs the tools to manage this: a compliant system must be able to accept remote curtailment signals, so the DNO can reduce or pause export during periods of network stress without sending an engineer to your door.
3. When G100 applies to your installation
The key trigger for G100 is grid export capability in a battery. If your battery can send electricity back to the grid, the G100 framework is relevant. A battery that only charges from solar or off-peak grid electricity and discharges entirely within your home, with no export path, operates under a different (generally simpler) framework.
In practice, most modern hybrid battery systems in the UK are set up to allow export, particularly once the homeowner registers for the Smart Export Guarantee (SEG). If you are earning SEG export payments, or plan to, and you have a battery rather than solar panels alone, your installer should have addressed G100 compliance as part of the installation. If you are not sure whether your system exports, check your inverter settings or ask your installer.
4. What a compliant installation looks like
For a domestic BESS installation with export, a G100-compliant setup typically involves the installer submitting a DNO notification before energising the system for export, confirming the system's protection settings meet the G100 specification, and in some cases ensuring the battery inverter supports the communication interface the DNO requires for remote curtailment. The exact requirements depend on the size of the system and the policies of the relevant DNO, so your installer should check with your network operator directly rather than assuming a one-size approach.
From the homeowner's point of view, the practical outcome is that your battery should be registered with your DNO for export, and the notification paperwork should appear in your installation documentation alongside the G98 or G99 notification for your solar panels if you have both. If your installer hands over a certificate pack that only mentions the solar panels and says nothing about the battery's export registration, it is worth asking the question before your system goes live for SEG payments.
Frequently Asked Questions
Does my solar battery need G100 approval?
If your battery can export electricity to the grid, G100 is likely relevant to your installation. Batteries that only charge and discharge within your home without any grid export may fall under a different framework. The safest position is to ask your MCS-certified installer explicitly which notification regime applies to your system and whether DNO approval has been submitted for grid export.
How does G100 differ from G98?
G98 covers small generation systems such as solar panels, wind, and micro-hydro. It was not designed for battery storage that can independently export to the grid. G100 fills that gap: it is the engineering recommendation specifically for Battery Energy Storage Systems connecting to the low-voltage network, including requirements for protection settings and, in some cases, the ability to receive and respond to curtailment instructions from the distribution network operator.
What happens if a battery is connected without proper notification?
Connecting a battery for grid export without the correct DNO notification is a breach of your grid connection obligations. The DNO can require disconnection, and you would not be eligible for Smart Export Guarantee payments on a non-notified system. Your MCS-certified installer is responsible for submitting the notification before the system is energised for export, and this should be confirmed in writing before you sign off on the installation.