G98 or G99? It's decided by the inverter, not the panels.

The rule

EREC G98 covers fully type-tested micro-generators up to and including 16 A per phase. On a normal single-phase supply that's about 3.68 kW. Anything bigger falls under EREC G99.

The 16 A is measured at the inverter's output. So the inverter's rating decides the route, not the total of the panels on the roof.

What it means for the paperwork

• G98: connect, then notify. You install and commission the system, then notify the network operator within 28 days, on G98 Form B. No permission is needed first.
• G99: apply first. You need the network operator's permission before you connect. Small systems can use G99's fast-track route, in place since November 2022, but it is still an application and a wait.

Why the inverter decides it

• More panels can still be G98. A 4 kWp array on a 3.68 kW inverter is G98: the inverter caps the output on the sunniest days, and you lose a little at the peak.
• A small array can still be G99. A 3.6 kWp array on a 5 kW inverter is G99, because the inverter can put out more than 16 A.
• Export limitation. If you want a larger inverter, network operators can accept an export limitation scheme (EREC G100) that caps what goes onto the grid. It is still part of an application, so plan the time.

Check before you quote

1. The inverter's rated output per phase, from its datasheet, not the panel total.
2. The supply. A three-phase inverter needs a three-phase supply. Most homes are single-phase.
3. The MPAN. Its first two digits name the network operator. Some homes, often on newer estates, sit on an independent network (an IDNO), and that operator is the one you deal with.
4. What's already there. Existing panels or a battery at the property can count towards the limit. Check before you add to them.

How Trident Solar does it

Trident works out G98 or G99 from the inverter's output current, not the array size. It refuses a three-phase inverter on a single-phase supply, checks the MPAN's check digit and names the network operator from it, says so when the home is on an independent network, and drafts the forms and the single-line diagram. For homes it designs automatically, it keeps the array within 3.68 kWp, so G98 is certain before anyone rings the customer.

Try it on a made-up house See Trident Solar

Sources: Energy Networks Association, connecting generation · MCS, notifying DNOs. Checked November 2026. Your network operator's own guidance is the final word for any job.