FREE CHECKLIST · FOR UK SOLAR INSTALLERS · 10 MIN READ

G99 Application Checklist for Commercial Solar (Free, Printable)

The short answer

A commercial solar job above 16A per phase (11.04kW three-phase) needs a G99 application before you install. Check the threshold, find the DNO from the MPAN and gather the site data; apply on Form A1-1 (under 50kW three-phase) or the ENA Standard Application Form; get and accept the DNO's connection offer in time; then commission, with witness testing if the offer asks for it, and send Form A3-1 within 28 days. Tick off the 24 steps below, or print them.

Checked 25 Oct 2026 against ENA, NGED, SSEN and Ofgem documents. Ticks stay on this screen only; nothing is saved.

1. Before you apply

Confirm it is G99, not G98G98 covers Fully Type Tested generation of no more than 16A per phase at a premises: 3.68kW single-phase, 11.04kW three-phase. Above that it is G99. Count generation already on site, and batteries: storage plant connecting to the network makes the customer a Generator too.
G98 limit explained →When a job needs G99 →
Find the DNO from the MPANThe first two digits of the MPAN on the bill identify the network operator. Some sites are on an IDNO network; the ENA says the process is almost identical. No meter yet? Ask the DNO whose area you think the site is in.
MPAN and DNO lookup →ENA: find my network operator
Talk to the DNO early and check capacityThe ENA guide says to discuss plans with the DNO before starting work, as early as possible, and points to the DNOs' capacity heat maps and surgeries. SSEN suggests checking its network map for anything of 50kW or more. Check your DNO's tools.
Capacity maps →ENA guide
Note the supply: MPANs, import, export, fault levelThe Standard Application Form asks for existing import and export MPANs, the site's import and export requirements, and the fault level contribution from the generation at the connection point. Record the supply capacity and any fault level figures you have.
ENA Standard Application Form
Draw the single-line diagram and site plansThe form asks for a single-line diagram of existing and proposed plant and warns that a diagram that doesn't match the technical data causes delays or rejection. Add a site layout plan (NGED asks for one at a suitable scale).
SAF (SSEN copy)NGED procedures
Survey the roof and the point of connectionCapture the roof, the main incomer and where the system will connect at the site visit, so the diagram and application match the building.
Commercial solar survey checklist →
Get inverter datasheets and Connect Direct Product IDsThe ENA Type Test Register closed on 16 April 2024 and moved to the ENA's Connect Direct portal. For Fully Type Tested equipment registered there, quote the Product ID. Otherwise send a Compliance Verification Report (Annex A.2 of G99), which the manufacturer completes and you submit.
ENA Connect Direct Compliance forms →
Decide whether export needs limiting (G100)Any export limiting scheme must comply with EREC G100. NGED wants its Export Limitation Scheme application form sent with the connection application. Other DNOs differ: check your DNO.
G100 export limitation guide →NGED export limitation

2. The application

Pick the formUnder 50kW three-phase (17kW single-phase): the simplified Form A1-1. Larger: the ENA Standard Application Form, which covers Type A over 50kW and Types B to D. Download it from your DNO (NGED and SSEN publish both), as each DNO has its own copies or portal.
Which G99 form →NGED forms SSEN forms
Complete the parts the DNO needs nowParts 1, 1a and 2 go in at first submission; NGED asks for Parts 1 to 3 as a minimum. Part 4 (per type of generating unit) must be updated before commissioning. Mark any estimated data as estimated and confirm it before commissioning.
SAF (SSEN copy)
Agree who submits and who signsThe ENA guide expects the installer to submit for the customer. NGED accepts agents working on the customer's behalf with their consent; SSEN wants a letter of authority where the applicant isn't the landowner or occupier. The customer signs the offer's letter of acceptance (NGED).
SSEN letter of authority NGED procedures
Attach everything in one goProduct IDs or compliance reports, the single-line diagram, site plans and any export limitation form. The ENA guide says to provide as much information as possible so the quote is as accurate as it can be.
What to gather →

3. DNO assessment and offer

Optional: budget estimate or feasibility studyA budget estimate is a desktop figure, not open for acceptance; the ENA guide gives 10 working days where the DNO does all the work, and SSEN says its estimates are free. Feasibility studies are charged for (ENA, NGED, SSEN).
SSEN quote options ENA guide
Know the quote timescalesLicence standards in the ENA guide: non-contestable work only, 30 working days LV, 50 HV, 3 months EHV; DNO doing all the work, 45 working days LV, 65 HV and EHV.
G99 timescales →
Check the feesSince April 2018 DNOs may charge Assessment and Design fees whether or not the offer is accepted, and apply them differently. SSEN doesn't charge to prepare quotes up to 50kW, though connection costs may apply. Check your DNO's Statement of Methodology and Charges for Connection.
ENA guide SSEN charges
Read the offer before the customer signsIt sets out the works, whether the connection is constrained, the costs and whether the DNO will witness commissioning.
ENA guide

4. Acceptance and installation

Accept inside the validity periodThe ENA guide says typically 30 to 90 days, with no guarantee a lapsed offer is made again. NGED offers last 90 days, with one 90-day extension possible if asked for in writing no more than 10 days before expiry.
NGED procedures
Sign the agreementsA Connection Agreement, an Adoption Agreement if an ICP builds contestable work, and an operating agreement for the interface. Some must be in place before construction starts.
ENA guide
Keep in touch while you buildAccepted offers can be withdrawn if a project isn't progressing. Track any reinforcement the DNO is doing, and tell the customer's export supplier the commissioning programme.
ENA guide

5. Witness testing, commissioning and Form A3-1

Book witness testing if the offer asks for itThe ENA guide says Fully Type Tested modules at LV aren't normally witnessed, and the scope, time and date go to the DNO at least 15 days ahead. NGED normally witnesses some tests where a site exceeds 50kW, wants 15 to 30 working days' notice, charges for it, and expects the installer to bring the test equipment.
NGED witnessing
Run the commissioning testsNGED says the installation must be complete and its supply available. Test to EREC G99 (NGED points Type A to section 16); EREC G99 Issue 2 is the current version, per the Distribution Code.
EREC G99 (ENA)Distribution Code
Send Form A3-1 within 28 daysThe Installation Document (Form A3-1), plus Form A2-4 where interface protection isn't type tested. The installer signs a declaration that the installation complies with G99. If witnessed, the forms can be handed to the DNO's engineer. For Type A, NGED treats it as the Final Operational Notification. Use your DNO's version.
SSEN commissioning forms ENA guide
Set up export paymentsOfgem's Smart Export Guarantee covers solar PV up to 5MW in Great Britain. The ENA guide says it needs a half-hourly export meter with an export MPAN, and MCS certification for solar PV up to 50kW.
Ofgem: SEG MCS guide →
Tell the DNO before any later changeReplacing or modifying protection or components, or adding capacity, must be notified to the DNO before it is made.
ENA guide

Link to this checklist

Free to share with your team, a customer or a forum thread. To link to it from your site, copy this:

<a href="https://solarsurveys.uk/guides/g99-application-checklist">G99 application checklist for commercial solar</a>

For the detail behind each step, see the G99 application guide, the DNO application guide and G98 explained.

G99 checklist: FAQ

Who submits and signs a G99 application?

The ENA's connection guide expects the installer to submit the application on the customer's behalf. NGED accepts agents working for the customer with their consent, and SSEN asks for a letter of authority where the applicant isn't the landowner or occupier. The customer signs the letter of acceptance on the DNO's offer, and the installer signs the declaration on the Installation Document (Form A3-1) after commissioning.

Is there a fee for a G99 application?

It depends on the DNO. The ENA guide says DNOs have been allowed to charge Assessment and Design fees since April 2018, whether or not the offer is accepted, and apply them differently. SSEN says it doesn't charge to prepare quotes up to 50kW, though connection costs may still apply. Feasibility studies are charged for, and NGED charges for witness testing. Check your DNO's charging statement.

How long does a DNO take to quote for a G99 connection?

The licence standards in the ENA guide are 30 working days at LV for non-contestable work only, and 45 working days at LV when the DNO does all the work (50 and 65 at HV). Reinforcement or a transmission assessment can add more, so check your DNO.

When is G99 Form A3-1 due?

Within 28 days of commissioning, per the ENA guide, with Form A2-4 if the interface protection isn't type tested. If the DNO witnesses the tests, the forms can be handed to its engineer on the day.

Sources

Opened on 25 Oct 2026. Where a rule is one DNO's own, the checklist names the DNO. The ENA's own pages for EREC G99, the Standard Application Form, Connect Direct and EREC G100 are linked as given in the ENA guide; always download forms from the DNO you are applying to. This is a summary, not legal or engineering advice.

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