G98 vs G99: why your solar installer caps the inverter at 3.68kW

Quick answer: Inverters rated 3.68kW or less per phase connect under G98: your installer fits the system, then notifies the network operator afterwards. Anything bigger needs G99 approval before installation, which usually takes four to eight weeks. An export limit can sometimes hold a larger hybrid inverter inside the G98 threshold, depending on your DNO.

What are G98 and G99?

They’re the two connection routes for plugging generation into the local electricity network, which is run by your DNO (distribution network operator), not your energy supplier. G98 covers small systems. G99 covers everything larger, and works more like a planning application.

Every grid-connected solar or battery system in Britain goes through one of these two routes. Your installer handles the paperwork either way; your job is understanding how the threshold shapes what they quote you.

Where does 3.68kW come from?

It’s 16 amps per phase at 230 volts, which multiplies out to 3.68kW. Most UK homes are single-phase, so 3.68kW of inverter output is the ceiling for the simple route. Three-phase properties get 16A on each phase, or 11.04kW in total, as Heatable’s G99 guide sets out (checked August 2026).

The threshold applies to the inverter’s rated output, not the panels. A 5kWp array behind a 3.68kW inverter is still a G98 job. That’s why so many UK quotes land on that oddly specific inverter size, and why inverter ranges all include a 3.68kW model.

How does G98 work?

It’s connect-and-notify. The installer fits and commissions the system, then sends the DNO the paperwork. Capture Energy notes the DNO can take up to four weeks to process the notification, but that happens after your panels are already generating. There’s usually no fee.

Under G98 there is no waiting period between survey and switch-on. For most three-bed homes that’s the whole attraction.

How does G99 work and how long does it take?

Above the threshold, the order flips: apply first, install after approval. Your installer submits the application with the technical details, and the DNO approves it, attaches conditions such as an export cap, or rejects it.

Heatable puts standard G99 decisions at four to eight weeks, and at eight to twelve in busy periods, with a fast-track of around two weeks for smaller qualifying systems. M&S Renewables reports eight to sixteen weeks in practice depending on the DNO and local network. Where the network needs reinforcement, Capture Energy warns costs can run to hundreds or thousands of pounds, and that’s the homeowner’s bill. Rare for domestic systems, but ask before you sign.

What is export limitation?

An export limit is a setting or device that caps what the system pushes to the grid at an agreed figure. Heatable notes a bigger inverter may be able to stay on the G98 route if its export is locked at or below 3.68kW, though it depends on the DNO and the exact setup. Your panels still run at full output for the house and the battery; only the exported surplus is capped. We cover the trade-offs in solar export limits explained.

An export limit caps what you send to the grid, not what your panels generate for your home. Batteries count too: Capture Energy confirms a standalone battery follows the same G98/G99 rules based on its own inverter rating.

What paperwork should you keep?

Three documents: the commissioning certificate, the G98 notification or G99 approval, and the MCS certificate. Keep digital copies of all of them the week the system goes live.

They matter later. Export tariff applications ask for proof the connection was registered. Buyers’ solicitors want the set when you sell. And any future battery or inverter change starts from what the DNO already has on file for your address. If your installer goes out of business, that folder is the only record that your connection was done properly. Chasing paperwork from a liquidator is nobody’s idea of fun.

Should you cap at 3.68kW or apply for G99?

For a typical three-bed roof with ten or twelve panels, a 3.68kW-capped hybrid inverter under G98 is the pragmatic choice. No waiting, no application risk, and the clipped export on sunny June afternoons is worth pennies.

The maths change if your roof takes 5kWp or more and you export a lot, since export income through the Smart Export Guarantee scales with what you’re allowed to send. If a battery or an EV is in your two-year plan, make one G99 application now rather than two applications a year apart. Each new inverter means going back to the DNO, and the second application is where capped systems get stuck.

FAQs

Who actually makes the application?

Your installer. Both Heatable and Capture Energy are clear it’s part of the installation service, and any admin fee should appear on the quote, not as a surprise.

Can the DNO refuse?

Yes. Refusals are uncommon for domestic systems, but the DNO can attach an export cap or ask for network reinforcement where the local network is constrained. You then decide whether to accept the conditions, pay, or resize the system.

Does adding a battery later trigger a new application?

Usually, because the battery’s inverter changes the total connected capacity. Mention battery plans at the design stage and your installer can size the original application to cover both.