In brief
Small systems up to 16 A per phase, which is 3.68 kW on a single-phase supply, connect under G98 and are notified within 28 days. Bigger systems, or solar plus a battery over that limit, need a G99 application approved before connection, sometimes with an export limit. Find your network operator through the ENA postcode search.
Your network operator, not your supplier
Two different organisations are involved in a home’s electricity. The supplier sells it and sends the bills, and you can switch supplier whenever you like. The network operator owns and runs the cables, substations and equipment that bring power to the street and into the house, and you cannot choose it: it depends on where you live. Solar connections are a matter for the network operator.
This guide does not name the operator for Crewe. Network areas were drawn long ago and do not follow modern town or council boundaries tidily, so the reliable way to find yours is to enter your postcode in the Energy Networks Association’s search. The firm installing the system should check it too, since the paperwork has to reach the right company.
G98: connect first, then notify
Most home systems fall under the G98 route. It covers generation up to 16 A per phase, which on the single-phase supply found in most homes equals 3.68 kW. A system within that limit can be installed and switched on, and the firm then notifies the network operator within 28 days. There is no waiting for permission.
The limit applies to the rating of the inverter, or inverters, rather than to the total of the panels. A firm may pair a little more panel capacity with an inverter that keeps within G98, because panels rarely produce their full rated output at once. That is a common and sensible design choice, but ask for it to be explained, and make sure any battery’s inverter is counted as well. Keep a copy of the notification with the rest of the system’s papers.
G99: apply first
A system that goes over the G98 limit, whether through a larger array or the addition of a battery, follows the G99 route. The firm applies to the network operator before installation, and nothing may be connected before the operator says yes. The operator looks at how the extra generation would affect the local network and may approve it as it stands, approve it with conditions or ask for changes.
Response times vary, so a G99 application should go in early. Ask the firm to confirm in writing that it will make the application, to send you a copy of the approval when it arrives, and not to connect anything before then. If an approval comes with conditions, the quote may need revisiting. Adding a battery is one way a modest system ends up in G99, as batteries in Crewe explains.
Export limits
An export limit caps the power a system can send to the grid at any moment. It is set in the inverter or a separate controller and measured at the supply point. A network operator may make a limit a condition of a G99 approval, and a firm may also design a system with a limit from the outset to keep a larger array or battery within what the network can take.
A limit does not stop the panels working. Power above the cap is used in the home, stored in a battery or, if neither is possible, simply not generated at that moment. On a bright summer middle of the day that can trim a little output, which is why any limit should be reflected in the generation estimate. How much a Crewe roof makes in each month, and when the surplus appears, is on export and self-use.
Single-phase and three-phase supplies
Most homes have a single-phase supply. A few larger houses, and some converted buildings, have three-phase, which spreads the load across three live conductors. Because the G98 limit is set per phase, a balanced three-phase system can be larger before it needs a G99 application, roughly 11.0 kW across the three phases. Whether a home has three-phase is usually clear from the meter and the cut-out, and the survey should record it.
The cut-out, main fuse and service cable
Where the supply enters the house there is a sealed cut-out containing the main fuse. It belongs to the network operator, as does the service cable feeding it. Nobody else should open it. A solar system connects on the household’s side of the meter, but the survey should still note the state and rating of the cut-out and fuse.
In some older properties, a single service cable is shared between neighbouring homes, an arrangement known as a looped supply. Where that is the case, or where the cut-out is old or damaged, the network operator may need to carry out work before a system is connected. That is for the operator to decide, and it can add time. The firm should raise it during the survey rather than on installation day; terraced houses covers the wider survey for older terraces.
Meters
To be paid for exported electricity under the SEG scheme, a home needs a meter that records what leaves the house as well as what comes in. In practice that usually means a smart meter. The electricity supplier, not the firm fitting the panels, normally arranges any meter exchange, so ask the supplier early. An export tariff also needs the system’s MCS certificate, so check the firm is on the MCS register before you sign.
Flats and shared buildings
In a block of flats, each flat usually has its own meter and supply, and the building has a separate landlord’s supply for shared areas. Panels feeding the landlord’s supply make one connection; panels feeding several flats make several, and the network operator may look at the building as a whole. Any project on a block should involve the operator early. Flats and solar explains the options for blocks.
Where the grid step fits in the timeline
The grid step sits at different points depending on the route. For a G99 system it comes early: after the survey and design, the firm applies, and nothing is ordered or fitted until the operator has replied. For a G98 system it comes at the end: the system is installed and commissioned, and the notification follows within 28 days. In both cases the export side follows on, because a supplier needs the MCS certificate and an export-recording meter before payments start. Ask the firm for a simple timeline that shows each of these steps and who is responsible for it.
What to ask the firm about the grid
- Which network operator serves the address, and how did you confirm it?
- Does the design fall under G98, or does it need a G99 application first?
- What inverter rating counts towards the limit, including any battery?
- Will there be an export limit, and is it reflected in the output estimate?
- Is there anything about the supply, cut-out or meter that the operator or supplier needs to deal with?
- When will I receive a copy of the notification or approval?
The wider checks on a firm are on choosing an installer. Buyers of a home with existing panels should ask for this paperwork, as buying a Crewe home with solar explains. Semi-detached houses with east and west slopes, which raise their own inverter questions, are covered on semi-detached roofs. A grid question about a particular home can go through the question form.