Between the home lanes and the full Standard Application Form sits one short form. Form A1-1 is the G99 application for generating modules with a total aggregate capacity under 50 kW three-phase, or up to 17 kW single-phase. It is the form for a large three-phase house, a shop, a small unit, a farm building, a village hall.
This is part 3 of DNO applications by size. It covers who lands on A1-1, what it asks for, what the operator does with it, and the sign-off that follows.
Who lands on Form A1-1
A job reaches A1-1 by one of three routes.
- It is over the SGI ceilings. The site is more than 32 A per phase with no export limiter, or 60 A or more with one. A 15 kW three-phase inverter is 21.7 A per phase; two of them on the same supply are 43.5 A per phase and need either a 32 A G100 scheme or Form A1-1.
- A unit is over 32 A. The SGI lanes cap each unit's rating at 32 A. A single 10 kW single-phase inverter is 43.5 A on its phase and goes straight to A1-1.
- A unit is not on the register. Every SGI lane requires fully type tested units. An inverter without a compliant ENA register entry uses A1-1, at any size.
Above 50 kW three-phase the simplified form stops and the Standard Application Form in part 4 takes over.
The single-phase ceiling is 17 kW
G99 section 7.6 sets the largest aggregate that can connect to a single-phase supply at 17 kW, and 34 kW on a split-phase supply. Above 17 kW per phase the operator expects three-phase units.
The same section deals with single-phase inverters on a three-phase supply. There is no need for intertripping between them up to 17 kW per phase, but the design should keep the imbalance between phases below 32 A in normal running. Form A1-1 asks you to confirm the balance where you use several single-phase units. Put one on each phase where you can and say so on the form.
What the form asks for
Form A1-1 follows the same shape at every operator, because it is an ENA standard.
- To the DNO. The operator's name and its submission address.
- The generator. That is the customer: name, address, contact, telephone, email and the MPAN or MPANs.
- The installer. Your company, your accreditation (MCS), address and contact.
- The installation address and its MPAN.
- Existing generating units, where there are any: the same table as below.
- The proposed units. For each: manufacturer, the approximate installation date, the energy source and conversion technology codes (solar is source R and technology 11; a lithium-ion battery is source S and technology 38), the manufacturer's reference number, the registered capacity in kW per phase at 230 V, and the power factor.
- The balance of single-phase units across phases, where relevant.
- A signature and date.
The manufacturer's reference number is the ENA Type Test Register's Product ID, where the unit has one. Including it lets the operator check the protection settings against the register instead of asking you for them.
Not every A1-1 unit is on the register. For those the operator may ask for the manufacturer's evidence of the G99 protection functions, the settings, and how the unit behaves on loss of mains. Have that evidence ready before you apply rather than after the operator asks.
Apply first, then wait
Form A1-1 is an application. Nothing is installed or commissioned until the operator answers, and the answer can carry conditions.
Form A1-1 asks for the approximate installation date of each unit rather than a target date with a rule attached. The 10-working-day to three-month window belongs to Form A1-2. Give a date you can hold, because the operator plans around it, and remember that a connection offer, where one is issued, is valid for three months.
The standard fixes the operator's clock for the SGI lanes at 10 working days. It fixes none for A1-1. In practice most operators run sub-50 kW three-phase applications as a fast track on a similar clock. Some quote longer, and an operator that decides it needs site-specific analysis will move the job onto its standard process, where an offer, and sometimes a charge, can follow. Read the operator's own connections page for the number it promises, and set the customer's expectation from that.
Where it goes
There is no single national portal for A1-1.
- Connect Direct takes the domestic G99 Type A lanes for homes under 17 kW per phase, and it decides the lane after submission. A three-phase house at 12 kW can go through it.
- UK Power Networks takes small generation through its Smart Connect installer portal.
- National Grid Electricity Distribution runs an online generation application.
- SSEN, Northern Powergrid, SP Energy Networks and Electricity North West take the form by email or through their own online forms.
Send the single line diagram with the form even when it is not asked for. A drawing that shows the inverters, the protection, the isolation, the meter and the point of connection answers the questions the operator would otherwise send back.
After commissioning: Form A3-1
Once the system is commissioned the operator gets the installation document, Form A3-1, within 28 days. It is in two parts.
Part 1 is the notice: the same customer, installer and unit details as the application, with the commissioning date and the register references.
Part 2 is the technical record: the schedule of protection settings, the as-installed data for each unit, the final circuit diagram, seven yes-or-no commissioning checks, and two declarations. Where the units are fully type tested the settings are the register's. Where they are not, the settings are the ones the operator agreed at application and you set on site.
The A3-1 is drawn from the installed system, not the design. If the inverter changed between application and install, or the capacity went up, that is a new application, not a note on the sign-off. Less than applied for is simply recorded.
Questions installers ask
Does a 12 kW three-phase house need an application?
Yes, unless every unit is on the register and the site is 32 A or under per phase, in which case it is SGI-3 on Form A1-2. A single 12 kW three-phase unit is 17.4 A per phase, so a listed unit takes the SGI-3 lane; an unlisted one takes A1-1.
Is there a fee for A1-1?
The application itself is usually free. A fee appears only where the operator moves the job onto its standard process and issues a connection offer with works in it.
Can I install while I wait?
No. G99 is apply-first above the connect-and-notify lanes. Scaffold can go up; the inverter cannot be connected. Installers who connect and hope are the ones the operator cites when it asks for tougher rules.
What if the operator asks for information?
The clock pauses until you answer. Reply on the same reference so the application stays one thread, and answer every point in one message rather than in pieces.
Solar Engine assembles the A1-1 from the design, the lead and your company record, with the units table filled from the catalogue and the register reference beside each unit. The fields the engine cannot know, such as the target date, are marked for you to type. The CRM sends the form and the drawing from your own mailbox and files the reply against the case.