DNO connection applications: who your network operator is and what to submit
- Your DNO is fixed by the installation postcode, not the energy supplier - use the Energy Networks Association postcode lookup at energynetworks.org to confirm the right operator before designing the system.
- G98 applies to systems at or below 3.68 kW single-phase and uses a notify-after-install process with a 28-day window; G99 applies above that threshold and requires written DNO approval before installation begins.
- A standard G99 application takes up to 45 business days, so it must be filed as soon as the system design is confirmed - not after the deposit is taken.
- The DNO acknowledgement letter or Connection Offer must be kept with the MCS certificate and delivered to the customer at handover - both are required for Smart Export Guarantee payments and property conveyancing.
- Adding battery storage to a G98 solar installation often pushes the combined output into G99 territory and requires a new application before the storage unit is connected.
Every solar or electrical install connects to one regional distribution network operator's area. This guide explains what a DNO is, how to identify the right one by postcode, and what documents to submit under G98 or G99 before installation can legally begin.
A Distribution Network Operator (DNO) is the licensed company that owns the physical wires, cables, substations, and transformers that carry electricity from the high-voltage transmission grid to homes and businesses. It is not the same as an electricity supplier - the supplier bills your customer for energy, but the DNO owns the infrastructure that delivers it. Every property in Great Britain sits inside one of six DNO groups' licence areas, and that area is fixed entirely by postcode: you cannot choose it and it does not change when a customer switches supplier. To find which DNO covers an installation address, use the Energy Networks Association (ENA) postcode lookup at energynetworks.org, or read the first two digits of the property's MPAN (Meter Point Administration Number, found on any electricity bill) against the ENA's distributor ID list. Once you know the DNO, what you send them depends on the size of the system and the technology type - but the process falls into one of two routes under Engineering Recommendations G98 or G99, and getting that determination right before the deposit is banked is what separates a job that flows from one that stalls.
The six DNO groups and how to confirm the right one
Great Britain operates 14 distribution licence areas across six DNO groups. Northern Ireland is outside this arrangement entirely and is served by NIE Networks under a separate regulator, the Utility Regulator.
The six GB groups are UK Power Networks (London, South East England, Eastern England), National Grid Electricity Distribution - formerly Western Power Distribution - (East Midlands, West Midlands, South West England, South Wales), Electricity North West (Greater Manchester, Lancashire, Cumbria), Northern Powergrid (North East England, Yorkshire), SP Energy Networks (Merseyside, Cheshire, North Wales, plus Central and Southern Scotland), and SSEN Distribution (Northern Scotland, Southern England). Each DNO group runs its own connections portal with its own form versions and submission email addresses.
The fastest way to confirm a DNO before quoting is the ENA postcode tool at energynetworks.org. A second check is the MPAN: the first two digits map to a specific DNO. Where boundaries are not obvious - the SP Energy Networks territory splits between Scotland and Merseyside, and SSEN covers two areas at opposite ends of the country - a postcode check is essential before completing any application form. Submitting a G98 notification to the wrong DNO does not reset the 28-day clock; it simply delays the process and forces a resubmission to the correct operator.
IDNOs are different
Independent Distribution Network Operators own the last stretch of wires on many newer housing developments. They are not geographically fixed and are regulated by Ofgem separately from DNOs. For a residential install on a new-build estate, confirm whether the property sits on an IDNO network before submitting to the area DNO.
G98 or G99: making the right determination before the job starts
The threshold that separates the two routes is 3.68 kW on a single-phase supply (16 A per phase) or 11.04 kW on a three-phase supply. Both Engineering Recommendations were updated to Issue 2 in March 2025.
G98 uses a notify-after-install approach. The installer commissions the system first, then submits a notification to the DNO within 28 days. Because G98-compliant equipment is fully type-tested and listed on the ENA type-test register, the DNO cannot refuse the notification - they log the generator on their network records and issue an acknowledgement, typically within 5 to 20 working days. The process is free of charge. The correct form is G98 Form B1 (individual installations) or Form A (multiple installations submitted together).
G99 requires prior written approval before any installation work begins. The installer submits a formal application - including full technical drawings and system specification - and the DNO then has up to 45 business days (approximately nine calendar weeks) to issue a Connection Offer. Many smaller residential G99 cases are turned around in four to eight weeks. A fast-track SGI (Simple Generation Installation) route is available for qualifying lower-complexity systems and can reduce the wait to around two weeks. Standard applications are free; costs arise only if the DNO determines that local grid reinforcement is needed, which is uncommon for typical residential systems but can reach into hundreds or, in constrained rural networks, thousands of pounds. The standard G99 form is Form A1.1; the fast-track is Form A1.2.
Adding battery storage to a system already notified under G98 commonly pushes the combined inverter output over the 3.68 kW threshold, which means the storage element requires a G99 application before the battery is connected - even if the solar installation itself originally qualified for G98. The combined integrated form A1.2 (for type-tested integrated microgeneration and storage installations) applies in this scenario if the fast-track criteria are met. Integrated solar-plus-battery systems that exceed the G98 limit from the outset require G99 from the start.
What the DNO letter is and why it matters
The DNO letter - the acknowledgement for a G98 submission or the Connection Offer for a G99 application - is the documented proof that the installation has been properly notified to or approved by the network operator. It is not optional paperwork.
For G98, the acknowledgement confirms that the DNO has logged the generator on their network records. For G99, the Connection Offer sets out whether the DNO approves the connection as designed, applies export limiting conditions, or requires modifications before approval can be granted. Outright rejections are uncommon for well-designed systems but can occur when local network capacity is insufficient. Where a G99 application is rejected or conditioned, installers can resize the system back under the G98 threshold, apply a G100 export limiter to cap grid export at an agreed level, or accept Active Network Management (ANM) terms that allow the DNO to curtail output during rare peak congestion periods.
The DNO letter should be stored alongside the MCS certificate. Both documents are required when the customer applies for Smart Export Guarantee (SEG) payments, when their home insurer asks about the installation, and when the property is sold - a buyer's solicitor will request both during conveyancing. Installers who file the DNO paperwork but do not deliver a copy to the customer are creating a problem that lands at the customer's door months or years later.
No exemptions exist
every grid-connected solar installation in Great Britain requires either a G98 notification or a G99 application. A system commissioned without either is not legally connected for export purposes, cannot receive SEG payments, and may invalidate the customer's home insurance. There is no minimum system size below which the notification is optional.
Step-by-step: submitting a DNO application
Confirm the installation postcode and identify the correct DNO
Use the Energy Networks Association postcode lookup at energynetworks.org before producing the quote. Record the DNO name and the relevant connections portal URL. If the property is on a newer development, check whether an IDNO rather than the area DNO is the correct recipient. Do not rely on assumptions based on county or region - boundary lines between licence areas do not follow county borders.
Determine whether G98 or G99 applies
Calculate the total inverter output across all generation and storage equipment. If the combined output is at or below 3.68 kW single-phase or 11.04 kW three-phase, G98 applies and you can proceed to installation. If the combined output exceeds those figures, G99 applies and you must receive a Connection Offer before any installation work begins. Where battery storage is part of the scope, check the combined output even if the solar-only element would have qualified for G98.
Prepare the application documentation
For G98: complete Form B1, providing the property address, MPAN, inverter make and model, rated output (kW), confirmation of type-test compliance, and a single-line electrical diagram of the installation. Check that the inverter appears on the ENA type-test register before submission - unlisted equipment cannot use the G98 route. For G99: complete Form A1.1 (standard) or Form A1.2 (fast-track, where eligible), supported by full technical drawings, the system specification, protection settings, and the inverter type-test certificate. Some individual DNOs use locally adapted versions of these ENA forms and require submission through their own portal - check the specific DNO's connections page before filing. Submitting the ENA standard form to a DNO that requires its own version will delay the application.
Submit the notification or application to the correct DNO
For G98: submit Form B1 to the DNO's designated connections inbox within 28 days of commissioning. Most DNOs have a dedicated small-scale generation address. The 28-day window runs from the commissioning date, not the installation date. For G99: submit before any installation work begins. Attach all required documents in a single submission. Note the submission date and the DNO's quoted response window (up to 45 business days standard; approximately two weeks for fast-track). The Connection Offer, when it arrives, has an acceptance deadline - typically 30 days - and accepting it formally unlocks permission to proceed.
Track the application as a job milestone and manage the DNO's response
Log the submission date and the expected response window against the job record so that any delay is visible before it affects the installation programme. For G99 jobs, the Connection Offer arrival is the critical gating milestone: installation cannot start until it lands and is accepted. If the offer is conditioned - for example, requiring an export limiter or ANM acceptance - return to the customer with the options before accepting, as each option affects the system's export income and the cost of the installation. Keep copies of all submission emails, reference numbers, and the DNO's responses in the job file. Project tracking software that lets you record each DNO milestone against the job means the office can see the status of every outstanding application without calling the installer.
Deliver the DNO documentation to the customer at handover
At practical completion, include the DNO acknowledgement letter (G98) or the accepted Connection Offer (G99) in the handover pack alongside the MCS certificate, commissioning sheets, and any warranties. Explain to the customer that these documents will be required for SEG applications and should be kept safely. If the G98 acknowledgement has not yet arrived at handover - the DNO typically responds within 5 to 20 working days - give the customer the submission confirmation email and reference number as a placeholder, and follow up with the formal letter when it arrives.
Capturing DNO details at commissioning
digital forms deployed to the installation team can capture the DNO submission reference, form type, and submission date at the point of commissioning - before anyone leaves the property. This removes the risk of submission delays caused by paperwork travelling from site to office and keeps the job file complete from day one. Zigaflow's eForms tool supports this kind of field data capture, with the completed record attached directly to the job.
Heat pump and EV charging DNO applications
Solar PV installers who also fit heat pumps or EV charging points face a parallel but distinct DNO notification process for those technologies. For heat pumps, the key threshold is the new Maximum Demand (MD) at the property. Where MD remains at or below 60 A, the installer can connect the heat pump and notify the DNO within 28 days using the ENA Single EV Charge Point and Heat Pump Installation Application Form. Where MD rises to between 60 A and 100 A, the installer must apply to the DNO before connecting and wait for the DNO's capacity assessment, which should be returned within 10 working days.
For multi-technology jobs - a solar PV and heat pump installation on the same property, for example - check whether both notifications can be bundled into a single multi-installation submission. The ENA multi-installation form exists for this purpose, and submitting once rather than twice reduces the administrative load and the risk of sending mismatched details about the same property to the same DNO.
Installers working across the renewables sector handle DNO applications as a routine part of every job. The risk sits with businesses that treat the application as an afterthought: a deposit taken, a kit ordered, and a G99 application filed the week before the scheduled installation date means a nine-week wait that nobody on the project accounted for.
Sources
- DNO Application for Solar UK: G98 (28 Days) vs G99 (45 Days)Smart Solar Homes · accessed 2026-09-29
- Notifying DNOs - MCSMCS Certified · accessed 2026-09-29
- UK Electricity Distribution Networks Map: Find Your DNO (2026)Selectra · accessed 2026-09-29
- What Is A DNO Application, And Why Do Need For Commercial Solar PanelsXcel Energy · accessed 2026-09-29
- What Is a DNO? Applications, Letters & Solar Explained | MyPlugInSolarMy Plug In Solar · accessed 2026-09-29