MCS vs G98 vs Part P: UK Solar and Battery Certification Explained
- MCS vs G98 vs Part P at a Glance
- MCS Certification for Solar and Battery Installations
- G98 Requirements for Small Grid-Connected Systems
- Part P Building Regulations for Domestic Electrical Work
- MCS, G98 and Part P Across Different Installation Scenarios
- Certificates and Records Homeowners Should Receive
- Planning Compliant Solar and Home Energy Storage
- Conclusion
- FAQs
Installing solar panels or home battery storage in the UK can involve several different standards, notifications and certificates. Although often lumped together, MCS, G98 and Part P are not three different forms of approval. They each cover a different component of a home energy installation.
MCS is about recognised standards for renewable small scale technology and for certified installers. G98 is about the interconnection and parallel operation of qualifying small generators to the local electricity distribution grid. Part P is about making electrical installations in dwellings safe, under the Building Regulations in England and Wales
Understanding these distinctions helps homeowners know which installer credentials to check, which documents to retain and when the Distribution Network Operator (DNO) or Building Control may become involved. This guide compares MCS vs G98 vs Part P, then explains how the requirements can overlap when installing solar PV or adding battery storage.
MCS vs G98 vs Part P at a Glance
The easiest method to comprehend the three is to consider installation quality, grid connection, and domestic electrical safety separately. It is possible that a single solar/battery project could affect all three areas, but meeting one criterion does not necessarily meet the others.
Different roles of MCS, G98 and Part P in a home energy installation
MCS is the recognised quality mark for small scale renewable energy technologies in the UK. It has standards for solar PV and battery storage, and contractors certified by MCS follow installation standards. An MCS certificate is associated with an installation made under that MCS certification programme.
G98, in contrast, is an Energy Networks Association engineering recommendation for qualifying fully type-tested microgenerators that are in parallel with the public low voltage distribution network. The standard G98 route is used where the generation of aggregate is in any phase does not exceed 16A.
Part P is about the safety of electrical installations in buildings that are used for dwellings. It is not used to certify renewable technology, but instead design and install relevant fixed electrical work safely.
Installation quality, grid connection and electrical safety as separate compliance areas
The three areas address different questions. MCS queries the recognised quality of the renewable installation and the certified installer. The G98 is a question to ask if a qualifying generator is able to connect safely to the distribution network and if the DNO has been provided with the necessary information. Part P deals with compliance of relevant domestic electrical work with Building Regulations.
For homeowners, keeping those responsibilities separate makes solar paperwork much easier to understand. It is also useful to consider a wider electrical safety check before major home-energy upgrades where the condition of existing wiring, circuits or the consumer unit is uncertain.
No one certificate can thus verify compliance to all aspects of an installation. An MCS certificate cannot be used in lieu of DNO requirements and a G98 notification cannot be used in lieu of electrical-safety requirements.
Situations where solar or battery projects may involve more than one requirement
The requirements can overlap, as they do in a new rooftop solar installation. The installer can install to MCS standards and the qualifying small inverter can follow the G98 connection route. Any fixed electrical work also has to meet electrical-safety requirements, as appropriate.
Overlaps can result from battery installations. MCS has a specific Battery Installation Standard to guide design and installation of electrical energy storage systems, and grid-connected battery inverters can impact the applicable DNO connection process.
The real lesson is that MCS, G98 and Part P are compliance fields, which can complement each other, and shouldn't be considered to be competing certificates. This is followed by examining MCS independently and what it means to be MCS certified for a solar or battery installation.
MCS Certification for Solar and Battery Installations
After the three compliance areas are split up, the simplest way of understanding MCS is as the quality and installation-standard system for small-scale renewable energy systems. It targets the design, supply, installation and commissioning of technologies like solar PV and battery storage by a notifiable and certified contractor, not just grid notification.
The role of MCS certified installers in small-scale renewable projects
An MCS certified installer has undergone an assessment against the requirements of the renewable technologies they install by an approved certification body. MCS certification therefore provides a method for homeowners to verify that a contractor is operating within acknowledged electrical or building industry standards, and not just with general electrical or building experience.
For a household planning PV, understanding the wider steps involved in setting up a solar panel system can also help put installer design, inverter choice and commissioning into context.
Technologies and installation standards covered through MCS
MCS technology-specific requirements are not a single renewable standard applicable to all projects. The MIS 3002:2025 is the current Solar PV Installation Standard that applies to MCS contractors who install, set to work and commission PV systems, and also supply and design PV systems. The MIS 3012 is also maintained by MCS and relates to electrical energy storage systems, design and installation of battery storage.
Such separation is important for combined projects. The contractor installing a solar PV system must also consider the applicable solar requirements and if battery storage is added, battery storage requirements. Therefore, MCS certification must be verified by the technology being used, and not taken as one blanket certification.
Consumer assurance provided by an MCS certificate and certified installation
An MCS certificate will provide evidence that installation has been designed, installed and commissioned to reflect applicable MCS standards and the use of MCS certified products where applicable. MCS states that the certificate is evidence of an installation carried out to industry recognised standards.
The certificate may have other uses as well as for the installation. MCS-related documentation may be required by homeowners under specific export tariffs or for providing proof of MCS installation. An MCS certificate should, however, be retained with DNO correspondence and electrical documentation as it doesn't replace G98 or Part P requirements.
Once the installer quality is understood, the next step is to understand G98 relating to the specific interaction of qualifying small generators with the local distribution network.
G98 Requirements for Small Grid-Connected Systems
Once MCS has considered the installation quality, G98 will be concerned with yet another issue: the way qualifying small generators are connected to and are able to operate on the public electricity network. Finally, for homeowners, the important thing to remember is that G98 is not a certificate for the installer, but a grid-connection and notification procedure.
The purpose of G98 for qualifying small electricity generators
Engineering Recommendation G98 is applicable to completely type-tested microgenerators that are connected in parallel with the public low-voltage distribution network. It establishes technical requirements to help ensure that small generation equipment can operate without causing an undue risk to the local network or to other electricity users.
This can apply to other qualifying distributed energy equipment, such as solar PV. The key is the way the generating equipment is connected and the total amount of capacity that is there, not whether the technology is solar or not.
The 16A-per-phase threshold applying to suitable G98 solar installations
The total registered generation for the normal route G98 should not exceed 16A per phase. This equates to about 3.68kW of generation capacity on a single-phase 230V system.
Generally, a qualifying G98 solar installation can go through the simplified “connect and notify” process. However, systems that are beyond the limits in the relevant G98 may require the implementation of G99 or another suitable DNO connection route, and the installation may require approval.
Installer and DNO responsibilities under the G98 connection process
The installer can install the qualified system first and provide the relevant G98 information to the Distribution Network Operator (DNO) within 28 days after the end of installation in a standard connect and notify installation. The DNO will check the notification and may request the installer to provide additional information if it is incomplete or incorrect.
Homeowners should keep the correspondence with their installation documents, as it will serve as proof that they have been notifying the local network operator.
For this reason, an MCS certificate and G98 notification are different: MCS is a part of the quality framework of the renewable installation, G98 is related to the interaction with the electricity network. The third area, however, is more concerned with the safety of the electrical work on your home performed by the electrician.
Part P Building Regulations for Domestic Electrical Work
Part P is for the safety of fixed electrical work in and around homes, where MCS is about the quality of renewable installations, and G98 is about how to connect renewables to the grid. For this reason, it is applicable to the electrical component of a solar or battery project and not a certification of the solar panels or battery storage technology.
Electrical safety requirements covered by Part P building regs
Part P building regs stipulate that any electrical work done in a building that is relevant to the dwelling needs to be designed and installed so that it is reasonably protected from fire and injury. In England, Approved Document P offers guidance on how to comply with this requirement, such as electrical design, installation, inspection, testing and certification.
In solar and battery installations, it is relevant to any new fixed wiring, circuit or other modification that is made to the household electrical installation. Compliance should therefore not be viewed as an afterthought and a paper trail to complete once the renewable-system design is complete.
Domestic electrical work affected by Part P electrical requirements
Not all minor electrical work is notifiable to Building Control, however, all fixed electrical work needs to be undertaken safely. Some work – for example fitting a new circuit or a new consumer unit – does require notification under Part P electrical guidance.
A contractor who is registered with an authorised Competent Person Scheme can self-certify work that qualifies and organise the necessary Building Regulations paperwork. If this route is not followed, then Building Control procedure may need to be followed separately.
It's a significant difference for homeowners: the electrician can provide the documentation for the electrical installations, and the Building Regulations compliance records cover the notification requirement.
Part P in England and Wales and different building-control arrangements elsewhere in the UK
Part P is relevant to the Building Regulations of England and Wales, with specific guidance available in each country. Wales has its own Approved Document P on Electrical safety in dwellings.
However, Scotland abides by the Building (Scotland) Regulations and Building Standards system and not Part P; therefore, homeowners should take note of the regulations applicable to the geographical location of their property.
The regional difference further emphasises that the homeowner shouldn't consider an MCS certificate, the G98 notification and Part P documentation interchangeable. The next step is to observe how these individual needs can be integrated in actual solar and battery installation situations.
MCS, G98 and Part P Across Different Installation Scenarios
The best way to observe how these requirements mesh with each other is to use them in actual household projects. Depending on the solar array design, a new solar array, battery retrofit and combined solar-and-storage installation may require varying levels of installer certification, grid notification and electrical compliance.
Compliance routes for a new rooftop solar PV installation
When installing a new rooftop PV, an MCS certified contractor can design and commission the roof PV installation to the applicable solar standard. If the inverter and aggregate generation do not exceed the G98 limit of 16A per phase, then the connect-and-notify route can be followed, and the DNO will be notified after commissioning.
Any fixed electrical work used for this purpose should also meet the domestic electrical-safety requirements. Homeowners wanting a broader overview of how panels, inverters and household wiring fit together can review solar panels and battery storage as a complete home system before discussing the detailed installation route with a contractor.
MCS, G98 and electrical compliance are not alternative pathways, but rather different aspects of the same project.
Requirements that may apply when adding battery storage to existing solar
Putting a battery into an existing PV installation is another case. A retrofit battery therefore has its own installation requirements, and MCS publishes MIS 3012:2025 specifically for the design and installation of electrical energy storage systems.
The requirements for a grid should also be rethought. A battery inverter that can import/export will impact the overall generation arrangement visible to the DNO. The connection process may vary depending on the type of inverter and configuration of the system, and may or may not result in a G98 project. Relevant energy devices must be registered with the DNO in accordance with Government guidance.
For new circuits and any major changes to the electrical system, compliance with the relevant Australian domestic electrical-safety standards must also be satisfied.
Combined solar-and-storage projects involving installer, electrical and grid considerations
Ideally, a household that installs solar panels and battery storage simultaneously should take all three compliance aspects into account during the system design phase, and not as separate compliance after the system has been installed. The MCS standards include both solar PV and battery storage; the route for DNO connection is based on the overall inverter and generation set-up.
Electrical work then has to be designed, installed, inspected and tested to meet the requirements of the Building Regulations and Electrical Wiring Regulations.
When planned in conjunction with one another, the risk of finding out later that an inverter exceeds the expected route, electrical work needs additional certification or battery equipment was not properly integrated into the original design can be reduced. Furthermore, once the installation path has been determined, homeowners should also be aware of what documents they should retain, as it is different for the MCS, G98 and Part P paperwork.
Certificates and Records Homeowners Should Receive
After the installation, homeowners shouldn't expect one document to be given to them for everything, and they should keep a good record of the work. The evidence produced as part of MCS certification and DNO notification is different to that of domestic electrical compliance and could be relevant to tariff, system upgrading, maintenance or if a house is sold.
Installation records associated with an MCS certificate
The MCS certificate should be given to the homeowner to confirm that the system has been designed, installed and commissioned to MCS requirements. The certificate is formal evidence that the installation meets MCS and replacement certificates may be requested if lost, MCS says.
Handover information can also consist of system specifications, commissioning records, warranties and guidance on operating the systems. Homeowners should keep these documents together, and the certificate is proof that the installation has been completed, while supporting documents detail the equipment that was installed and how to maintain it.
DNO acknowledgement and paperwork commonly described as a G98 certificate
When looking for what a G98 certificate looks like, homeowners should know that G98 typically doesn't issue a standard consumer certificate that's comparable to an MCS certificate. However, after commissioning a qualifying system, the installer provides the DNO with the appropriate information from the G98 Installation Document.
The DNO then registers the installation and can follow up with the installer if there are inaccuracies or omissions in the notification. It is therefore recommended that the homeowner keep the notification sent, the DNO acknowledgement or correspondence and the inverter/type-test information provided with the project.
Maintaining these records is especially helpful in case the system is expanded at a later time, as a new inverter, new solar power or battery storage may alter the grid-connection route.
Electrical and Building Regulations records associated with a Part P certificate
If the work is applicable to the homeowner's domestic electrical work, they could be given more than one document. Completed work should be inspected and tested with the appropriate electrician's certificate for electrical installation. If the work is self-certified by a Notifiable Work competent person scheme, the homeowner should also get a Building Regulations certificate.
Note that these records are not the MCS certificate or G98 paperwork. Each illustrates an aspect of the project:
MCS certificate: evidence of an installation registered under the MCS framework.
G98/DNO records: evidence that qualifying generation has been notified to the local network operator.
Electrical/Part P records: evidence relating to electrical testing and Building Regulations compliance where applicable.
Having all three types of paperwork in one place makes it much clearer what is going on in the installation. It can also facilitate the assessment of future maintenance, battery retrofits or other solar and battery system upgrades easier to assess because the next installer can see how the existing system was originally designed and documented.
Planning Compliant Solar and Home Energy Storage
With the understanding of the required certificates, grid notifications and electrical records, homeowners can then be better positioned to make a decision on the energy system itself. Compliance must be taken into account in the system design, and not after equipment has been purchased, especially where solar generation and battery storage will interface with the household wiring and distribution system.
Compliance checks before choosing a solar and battery storage system
Check the compliance route to ensure that proposed inverter size, battery installation, wiring and installation etc., do not impact this route before making a solar and storage system selection. A competent installer should determine the need for MCS standards, if the project is G98 or will need a different DNO procedure and if electrical or Building Regulations documentation is required.
Useful checks include:
Existing solar and inverter specifications if storage is being added later.
Proposed inverter output and whether it affects the current DNO connection arrangement.
Condition and capacity of household circuits and the consumer unit.
Installer certification for the solar or battery technology being fitted.
Handover documentation that will be provided once commissioning is complete.
For existing systems, understanding what retrofitting means for home energy upgrades can also help homeowners distinguish between adding storage to current equipment and replacing the original solar installation.
EcoFlow STREAM 5000 for households planning solar and storage together
EcoFlow STREAM 5000 is ideal for households that haven't yet installed solar panels, allowing them to plan solar generation and battery storage from scratch. This can help to think about what happens in the future for electricity demand, the inverter size and what needs to be installed, as one project rather than as separate pieces to be added on.
The system itself does not remove the need to follow applicable MCS, DNO or electrical requirements. Those compliance steps should be confirmed as part of the installation design.
EcoFlow STREAM 5000 AC for existing solar homes adding battery storage
Homes that already have solar panels present a different scenario. EcoFlow STREAM 5000 AC is intended for homeowners adding battery capacity to an existing photovoltaic installation, making it more relevant where the priority is to retain more solar electricity without replacing the original panels.
In the case of a retrofit, the inverter should be inspected and electrical documentation and records should be reviewed by the installer prior to installing the new storage. This is especially important as the addition of a battery can change the overall grid-interactive configuration even though the original solar panels are the same.
The overall takeaway for MCS vs G98 vs Part P is thus that selecting quality hardware is just one step in a compliant installation. Prior to commissioning solar or battery equipment, system design, installer competency, network requirements and complete documentation should all be considered in the same context.
Conclusion
Once each requirement is considered in isolation as part of a separate compliance area, understanding MCS vs G98 vs Part P becomes much easier. MCS covers standards for renewable installations, G98 is for recognised standards for small generators that are connected to the local distribution network, and Part P is for domestic electrical safety under Building Regulations in England and Wales.
The takeaway for homeowners is no one document replaces the others. Depending on the design and location of the solar or battery installation, a solar or battery project might require a MCS certificate, G98 records and separate electrical or Building Regulations documentation.
This is the same for battery storage added later. The existing inverter capacity, the grid-connection records and the electrical situation should be checked prior to system expansion. Original certificates and commissioning paperwork makes future upgrades much easier to gauge.
EcoFlow STREAM 5000 is an expandable home-energy route for households starting with solar and storage simultaneously, and STREAM 5000 AC is ideal for homeowners with pre-existing solar installations who are looking to install battery storage.
FAQs
Is an MCS certificate legally required for every UK solar installation?
No, MCS itself states that an MCS certificate is not a mandatory legal requirement for every solar installation. However, MCS certification can be important when homeowners want to access certain export tariffs, warranties, finance arrangements or other schemes that require evidence of an installation completed to recognised standards.
This is separate from electrical-safety and DNO obligations, which may still apply even where the homeowner chooses a non-MCS installation.
Can the same installer handle MCS, G98 and Part P requirements?
Potentially, yes, but only where the installer or installation company holds the appropriate registrations and competence for each part of the work. An MCS-certified solar contractor may also employ electricians registered with an authorised Competent Person Scheme and may submit the necessary G98 information to the DNO.
Homeowners should therefore check the contractor’s actual credentials rather than assuming MCS certified status automatically covers every electrical and Building Regulations responsibility. Competent Person registration is specifically what allows qualifying tradespeople to self-certify certain Building Regulations work.
Can missing solar or electrical compliance documents be replaced later?
Sometimes, if an MCS certificate has been lost, MCS provides a process for requesting installation-certificate information or a replacement. Electrical or Building Regulations records may also be recoverable through the installer, certification scheme or relevant Building Control records, depending on how the original work was notified.
However, replacing missing paperwork is easier when the installation was properly registered in the first place. Homeowners should therefore keep MCS, DNO and electrical records together from the date the system is commissioned.
Can you install home battery storage without solar panels?
Yes. A battery does not necessarily need solar panels because it can charge using electricity from the grid. This can allow households to store electricity during cheaper tariff periods and use it later when grid electricity is more expensive. Energy Saving Trust specifically notes that storage technologies can provide value even without solar generation.
Before choosing battery-only storage:
Compare daytime and off-peak electricity tariffs.
Size storage around realistic household consumption.
Check installation, inverter and DNO requirements.
Solar can be added later if the property and system design allow it, so battery-only storage can form part of a longer-term home-energy plan.
Can a home battery storage system provide backup power during a grid outage?
It can, but backup power is not automatic with every battery installation. The battery and electrical system need to be specifically configured for backup or off-grid operation; some standard grid-connected batteries stop supplying household circuits during an outage.
Before installing storage for resilience:
Confirm whether the system supports backup operation.
Identify which circuits and appliances can remain powered.
Compare usable capacity with expected outage demand.
Homeowners considering resilience can also compare home battery backup and generator options to understand how different backup approaches serve essential household loads.