Grid Connection for Business Solar: Will the Network Let You Connect?

Will the grid let my business connect solar?

Usually, yes, though not always at the size or export you first want. The network operator owns the cables and substations that bring power to your site. Solar can push power the other way, so the operator checks the local network can take it.

The 16 A threshold is in the Energy Networks Association's G98 guidance (ENA), and National Grid Electricity Distribution says generation over 16 A (3.68 kW) per phase must comply with G99 (NGED). The detail of applications is the installer's job.

Who runs the network where your business is

Ofgem lists 14 electricity distribution network operators in Great Britain, owned by six groups (Ofgem). Each covers a fixed area. Northern Ireland has its own operator, NIE Networks.

Boundaries don't follow county lines exactly, so check your site's postcode with the Energy Networks Association's look-up (ENA) or an operator's own tool (SSEN). The network operator is not your electricity supplier: you can change supplier, but not operator.

What the network operator checks

• The size of the system. Its rated capacity, including any battery and anything already generating on site
• How much it will export. Most businesses use much of their output, but the operator plans for the maximum export
• The local network. Whether the cables, transformer and substation can take the extra power
• The equipment. Type-tested inverters and protection that disconnect safely if the grid goes down

SSEN says that for generation of 50 kW or less you generally won't need to worry about network capacity constraints or reinforcement costs in most areas, and that for 50 kW or more it is worth checking its network map for constraints (SSEN). Operators publish capacity and opportunity maps; National Grid Electricity Distribution's is one example (NGED).

Export limits and zero export

If the operator says the network can't take the full export without costly or slow reinforcement, a business can limit its export instead. National Grid Electricity Distribution explains that an export limitation scheme measures the power at the site's connection and restricts generation or storage so the agreed export capacity is not exceeded. It must comply with the standard G100, be fail-safe, and bring export back under the limit within 5 seconds (NGED).

• Export-limited. Generate as much as you like, export up to an agreed figure
• Zero export. Generate up to what the site is using, export nothing
• When it suits. Businesses that use most of their output in the day, which is most of the businesses that suit solar
• The cost. Some output may be curtailed on quiet days; a battery can store it instead

Export earns less than the electricity it replaces on site in most cases: see the Smart Export Guarantee.

Timescales

There is no single answer. Small systems on the fast track routes move quickly; larger systems that need a network study, an offer and possibly reinforcement take longer, and each operator publishes its own process and timescales. In Northern Ireland, NIE Networks runs its own versions of the rules, G98/NI and G99/NI (NIE Networks). Ask your installer to check the capacity map for your area at the survey, and to give you the operator's current timescale before you sign.

Batteries and grid limits

A battery counts towards the capacity the operator looks at, but it can also help when export is limited: it stores output the site can't use at midday instead of curtailing it. The connection application covers the solar and the battery together. See commercial battery storage and system sizes, where the rules change by size.