Solar Export Limits Explained: G98, G99 and DNO Caps in Plain English

Quick answer: if your inverter can push no more than 16 amps per phase into the grid — about 3.68 kW on a normal single-phase supply — your installer can fit the system first and notify your network operator within 28 days afterwards under a process called G98. Anything bigger needs G99 pre-approval from the DNO before installation, which can take several weeks. An export limitation device lets you install a larger system while capping what flows to the grid, so you keep the full output for your own use without the G99 wait.

First, meet your DNO

Your Distribution Network Operator (DNO) owns the cables and substations in your street — it is not your energy supplier. In most of the North West that is Electricity North West; other regions have their own operator. Every generator connected to their network, including a domestic solar system or home battery, has to be registered with them under connection rules written by the Energy Networks Association. The two that matter for homes are G98 and G99, and the dividing line is that 16-amps-per-phase figure.

G98: fit and inform

G98 covers “fully type-tested micro-generators” up to 16A per phase — in practice, a standard single-phase home with an inverter rated at 3.68 kW or less. The process is deliberately light-touch:

• Your installer fits and commissions the system with no advance permission needed
• They then notify the DNO within 28 days of commissioning
• There is nothing for you to do and no fee — a competent installer handles it invisibly

This is why so many UK systems are designed around a 3.68 kW inverter even when the panels on the roof add up to more — a 5 kWp array feeding a 3.68 kW inverter is a perfectly normal, G98-compliant design. Panels rarely produce their full rated output in UK conditions, so the “oversizing” costs less generation than you might think.

G99: permission first

Cross the 16A threshold — a bigger inverter, a second inverter alongside an existing system, or a battery that takes combined capacity over the line — and the order flips: the DNO must approve the connection before installation. Expect:

• An application made by your installer with system specs and a site plan
• A statutory assessment window — straightforward domestic cases often clear in a few weeks, but complex ones or constrained local networks can take longer
• A possible connection offer with conditions — including, sometimes, a requirement to limit export
• In rare cases, a quote for network reinforcement if the local grid cannot take the extra export

The practical advice: on any G99-sized job, get written confirmation that the DNO application is approved before you pay a substantial deposit or book scaffolding. A good installer will insist on this sequence anyway.

Export limitation: the middle path

An export limit caps the instantaneous power your system can send to the grid, enforced by the inverter itself using a CT clamp on your incoming supply. It does not cap generation — everything above the limit can still run your appliances, heat water via a diverter or charge a battery. It only trims what you sell.

That makes it useful in two situations:

• You want a big array on a single-phase supply — e.g. a 6 kW system export-limited to 3.68 kW, keeping the connection paperwork simple while you self-consume the surplus
• The DNO offers a constrained G99 connection — accepting an export cap can turn a refusal or an expensive reinforcement quote into a quick yes

What does a cap actually cost you? Less than intuition suggests. UK roofs only exceed 3.68 kW of surplus export during the sunniest midday hours of summer — and if a battery is soaking up the spare output first, the clipped slice shrinks further. For most homes the lost export income is a small percentage of annual generation value; a hybrid inverter and battery turns most of it into savings instead. If maximising paid export matters to you, our guide to Smart Export Guarantee income covers the tariff side.

What this means for your SEG payments

The Smart Export Guarantee pays you per kWh actually exported, measured by your smart meter — Ofgem’s scheme rules require MCS (or equivalent) certification and a meter capable of half-hourly export readings. An export limit simply means your peak export is capped; every kWh under the cap is paid as normal. Nothing about G98, G99 or export limitation changes your eligibility.

Questions to ask your installer before you sign

• Is this system G98 or G99 — and who is handling the paperwork?
• If G99: has the application gone in, and is the quote conditional on DNO approval?
• Is the design export-limited? To what figure, and is that limit DNO-approved?
• Does the inverter chosen support export limitation natively (most modern inverters do, including microinverter systems — see our micro vs string guide)?
• If I add a battery later, will that trigger a new application?

Frequently asked questions

Is 3.68 kW the biggest solar system I can have?

No — it is the biggest inverter export you can connect without prior permission on single phase. Your panel array can be larger than the inverter rating, you can apply for G99 approval for more, or you can export-limit a bigger system. Plenty of UK homes run 5–8 kWp perfectly legally.

Do batteries need DNO approval too?

Yes — the G98/G99 rules cover any device that can export, and a battery can. Adding storage to an existing system usually means a fresh notification or application covering the combined capacity, which your installer should handle.

Can I raise my export limit later?

Usually, by applying to the DNO under G99 — approval depends on local network capacity at the time. If you are replacing a failed inverter anyway, that is a sensible moment to review it: see our inverter replacement guide.

Sizing a system and want to see what the numbers look like for your roof? Try the free savings calculator, read the solar panel cost guide, or register your interest for installer quotes when our comparison service launches.