G98 and G99 are the two rulebooks for connecting solar panels to the UK grid. If your system is small, G98 applies, and your installer simply notifies the network operator. If it is larger, G99 applies, and you must get approval before you switch on.

The dividing line is 16 amps per phase. On a normal single-phase home, that is 3.68kW. So the size of your inverter and battery setup decides which route you take. This guide explains both routes in plain English, as of October 2026.

What G98 and G99 actually are

Both are engineering recommendations written by the Energy Networks Association, the trade body for the UK’s network operators. They set the technical rules for connecting small generators. The aim is to keep the local network safe and stable, because many homes now feed power back.

Your local network operator is called a DNO, short for distribution network operator. It owns the poles, cables and substations near your home. It is not your energy supplier, so you do not choose it.

G98: small systems, notify afterwards

Electricity North West explains that G98 covers all generation up to 16 amps per phase. That is 3.68kW on a single phase and 11.04kW on three phases. Many homes with a modest roof array fall under this route, but your installer must confirm it.

The timing is the point that confuses people. MCS says the DNO needs to be told within 28 days of commissioning for a G98 system. Installers complete a form called G98 Form B. However, individual network operators word their own guidance differently, and one says to notify before you connect. So let your installer confirm the rule for your area.

You do not need to wait for approval under G98. You also do not usually need to do the paperwork yourself. Ask your installer to give you a copy of the notification.

G99: bigger systems, apply first

If the system is above 16 amps per phase, G99 applies. MCS says the installer must apply to the DNO before connecting new equipment. They use the G99 application form, and then they wait for an answer.

For most homes, G99 Type A is the relevant category. It covers systems above 16 amps per phase and below 1MW, according to SSEN’s summary guides. Homes and small businesses sit well below that top limit, but the process is the same.

A G99 application takes time. The DNO studies the local network, so it may approve the full export, limit it, or ask for upgrades. For this reason, ask your installer how long it expects the process to take in your area. The response time varies between operators, so plan for a wait.

How the 3.68kW limit works in practice

Network operators describe the limit as covering the generation at your property. It is not a limit per device. For example, if you add a second inverter or a battery later, the total can pass the line, so G99 may apply.

Three-phase homes have a higher G98 limit of 11.04kW, which is 16 amps on each of three phases. Most UK homes have a single-phase supply, so 3.68kW is the figure that matters. First, check which supply you have before you plan a larger array.

Your installer should work this out at the survey. Our guide to solar inverters explained shows how inverter size relates to panel size. It also explains why a smaller inverter can still work well.

Batteries and the grid

A battery is part of the same connection process. The Electricity North West page notes that storage is exempt from some G99 requirements, but it must still meet others. So tell the installer about any battery plans now, even if you will add one later.

Adding a battery to an existing system can change your route, so read our guide to solar battery cost and sizing before you decide. Then ask the installer to check whether the combined output stays below the limit.

Why the DNO connection matters for money

You need a correct connection to get paid for exports, because suppliers check it. To join a Smart Export Guarantee tariff, Ofgem says suppliers with over 150,000 customers must offer one. Your installer and system must also be MCS certified, or certified by an equivalent scheme. We cover the money side in the Smart Export Guarantee explained.

A missing DNO notification can cause trouble later, too. So keep the notification confirmation with your other solar papers, because a buyer or insurer may ask for it.

What to ask your installer

Use these questions at the quote stage, and then compare the answers.

  • Is my system under or over the G98 limit?
  • Will the plan include a battery, now or later?
  • Who files the DNO paperwork, and when?
  • What happens if the DNO limits my export?
  • Do I get a copy of the notification or approval?

Our guide to choosing a solar installer has a fuller checklist. The Smart Export Guarantee and battery hub shows how export limits affect your income.

Other approvals to line up

The grid is one of several approvals. For example, roof panels usually do not need planning consent, but check first. Read do solar panels need planning permission for the exceptions.

An MCS certified installer should also handle the paperwork, but ask to see it. See MCS certification explained for what that covers. Our hub on how to plan a solar installation puts all the steps in order.

Costs, winter output and diverters

Network operators may charge for some connection work, especially under G99 when upgrades are needed. Most small G98 notifications are routine. However, if a charge appears, ask for it in writing before you sign. Our post on 0% VAT on solar panels and batteries explains how tax affects the quote.

Winter output rarely changes the connection route, because size is what counts. But it does change how much you export. See solar panels in winter for what to expect. If you plan to send spare power to a hot water tank, read about solar diverters for hot water.

If you want the basics of how panels, inverters and the grid link up, start with how domestic solar panels work.

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Common questions

What is the difference between G98 and G99?

G98 covers small systems up to 16 amps per phase, which is 3.68kW on a single phase. G99 covers larger systems and needs approval before you connect.

Do I need DNO approval for solar panels?

Only for G99 systems. A G98 system is notified to the network operator, normally within 28 days of commissioning. Your installer handles the forms.

Who pays for a G98 or G99 application?

Your installer normally files it as part of the job. Network operators may charge for some G99 work or for network changes. Ask for any such cost in writing before you sign.

Do I need to tell the DNO about a battery?

Yes, batteries are part of the connection process. Your installer should include any battery in the application or notification. Ask them to confirm this.

Can I be refused a connection?

A G99 request can be refused or limited if the local network cannot cope. The operator may offer a reduced export limit instead. Ask your installer about this early.