The answer first
Find the network operator for the address with the Energy Networks Association postcode search. Systems whose inverters total no more than 16 A per phase, about 3.68 kW on a single-phase supply, connect under G98 and are notified within 28 days. Larger systems, or panels plus a battery over that limit, need a G99 application approved before connection.
Who runs the local network
Two different companies are involved in a home’s electricity. The supplier sells the electricity and sends the bill, and a household can switch supplier whenever it likes. The distribution network operator owns and runs the cables, substations and overhead lines that carry electricity to the house, and which company that is depends only on where the house is. It is the network operator that needs to know about a solar system.
The Energy Networks Association’s “find my network operator” search gives the operator for any postcode. This guide does not name one for Nantwich: the search is the reliable source for a particular address, and it also gives the operator’s contact details for connections.
G98: connect, then notify
Most household systems connect under the engineering recommendation known as G98. It covers equipment with a total rated output of up to 16 A per phase, which on a single-phase supply is about 3.68 kW. What counts is the inverter’s rating, not the panels’, so an array of somewhat more than 3.68 kWp on a 3.68 kW inverter still falls under G98. The system can be switched on first, and the operator must then be notified within 28 days. The installing firm normally sends the notification; ask for a copy, because a buyer of the house may ask for it later.
Everything at the address counts together. Panels already on the roof, a second array on a garage, a battery with its own inverter: all of their ratings are added up when deciding whether the limit is reached.
G99: ask first, then connect
Above the G98 limit, the system falls under G99. The firm, or the household, applies to the network operator with details of the equipment and the site, and nothing may be switched on until the operator’s approval arrives. The operator studies how much more generation the nearby cables and transformers can take. Its answer can be a straightforward approval, an approval with conditions, or a statement that the network needs work before the system can join it. How long that takes varies with the operator and the location, so a G99 job should not be given a fixed installation date until the approval is in hand.
A common condition is an export cap: the system may generate as much as it can and supply the house in full, but the flow out to the grid must stay below an agreed level. Settings in the inverter or a separate control device enforce it. A cap changes the balance between self-use and export, explained on export and self-use, so find out whether one is likely before deciding on the size of the system.
Batteries and the limit
Whether a battery runs through its own inverter or through a hybrid unit shared with the panels, its rating is added in when the G98 limit is worked out. A modest solar system that sits comfortably inside the limit can be pushed over it by adding a battery, turning a simple notification into a G99 application. Ask the firm to state the combined inverter rating on the quote and say which route it will follow. Storage is covered more fully on batteries.
Single-phase and three-phase supplies
Almost all homes have a single-phase supply. Because the G98 limit is set per phase, a property with a three-phase supply, such as some farms and larger houses, can usually connect a bigger system on a simple notification. Converting a single-phase supply to three-phase is work for the network operator, can involve new cables to the property, and can be expensive, so it is rarely worth doing for solar alone. If it is being considered, get the operator’s quotation before the solar design is settled.
Long rural supplies
Around Nantwich, the village wards are made up largely of detached houses, between 49.9% and 65.9% of households against 36.6% across Cheshire East, and many rural properties sit some distance from the nearest substation. In general terms, a long overhead line serving a few properties behaves differently from a dense town network. When solar systems export, the voltage at the far end of a long line rises; on a bright day with little local demand, it can rise far enough for inverters to switch themselves off for protection. Operators take this into account when assessing G99 applications on rural lines, which is one reason conditions such as export caps are more likely there.
A household at the end of a long lane can still have solar. It is worth asking the firm whether it will check the supply voltage at the property, whether the inverter’s settings suit the local network, and whether the design keeps within G98 or needs G99. The heating and outbuilding questions that often come with a village house are on off-gas villages, and the cable runs for garden arrays on ground-mounted panels.
More than one supply
Some rural properties have more than one connection, for example one to the house and another to a barn or workshop. Panels on an outbuilding can be connected to whichever supply is nearest, but each connection is treated separately, and the export tariff follows the meter the system feeds. Make sure the quote names the supply, and that the notification or application refers to the right one. If an outbuilding has no supply of its own, the panels connect back at the house, and the length of that cable run becomes part of the design, as described on ground-mounted panels.
The meter
To be paid for exports under the SEG scheme, the house needs a meter that records electricity flowing out as well as in, usually a smart meter. The electricity supplier, not the network operator, arranges the meter. Check that it is in place, and recording exports, soon after the system is switched on. If the house still has an older meter that counts only imports, ask the supplier how soon it can be changed, because exports before the change go unrecorded.
Power cuts
Grid-connected inverters are designed to switch off when the network goes down, so that no power flows back into cables that engineers may be working on. A standard solar system therefore does not keep the house running in a power cut. Systems with a back-up function use extra switching equipment to isolate the house before supplying chosen circuits, and that equipment must be designed and installed for the purpose.
Changing the system later
Adding panels, adding a battery or replacing an inverter with a larger one changes the connection. The operator must be notified again, or a new G99 application made if the total goes over the limit. Keep the original paperwork, since the next firm will need it, and record any changes alongside the MCS certificate, which an installer on the MCS register issues.
A short checklist
- Look up the network operator for the postcode.
- Ask for the combined inverter rating on the quote, including any battery.
- Confirm whether the job is G98 or G99, and who handles it.
- For G99, wait for approval in writing before the system is switched on.
- Keep copies of the notification or approval with the house papers, as listed on buying a home with solar.
Registers and questions for vetting a firm are gathered on choosing an installer. For a question about a particular supply, use the question form.