DNO G99 connection for commercial solar in the UK
Grid capacity — not planning or capex — is now the single biggest blocker to UK commercial solar. Here's how G99, G100 and ANM shape connection timelines and how to sequence your application.
The G99 application process
1. Fast Track vs Full Study
Under 50 kW three-phase you usually qualify for G99 Fast Track (28-day decision). Above that, or in constrained zones, expect a Full Application requiring detailed studies and a fee (£1,000–£5,000+).
2. Connection offer
Timelines vary massively by DNO and region. Straightforward offers land in 65 working days; constrained networks may take 6–12 months and include reinforcement cost estimates from £10k to £2M+.
3. Accept and pay
Offers are typically valid for 3 months. Reinforcement costs and pre-construction milestones lock in when you accept — think carefully before signing.
4. Commissioning & G99 witness test
Before energising, your inverter must pass a witness test on the site's protection relays. Most DNOs delegate this to accredited installers on standard inverters.
How to avoid reinforcement
Options in order of impact: G100 zero export, ANM curtailment, oversizing DC vs AC (clipping), pairing solar with battery, and load-shift agreements. Together these can unlock connection in months rather than years.
Related reading
FAQ
What's the difference between G98 and G99?
G98 covers small-scale (≤16 A/phase, so ~3.68 kW single-phase or ~11 kW three-phase) — notification only. G99 covers everything above that, including all commercial solar.
How long is the DNO queue in 2026?
For projects up to 500 kW export: usually 3–12 months from application to energisation. Above 1 MW export in constrained regions (East England, parts of Scotland): 18–36 months and reinforcement costs are common.
What is G100 zero-export and when should I use it?
G100 caps export at zero (or a defined limit). Because the network sees no additional export, connection is far quicker and reinforcement is avoided. It's the standard route for sites where self-consumption is >75% — including cold storage, factories and 24/7 logistics.
What's an ANM zone?
Active Network Management zones let more generation connect to a constrained network by curtailing output when the network is congested. You'll get faster connection and lower cost, but expect 3–10% of forecast output lost to curtailment annually.
Can I add battery storage under the same G99 application?
Yes — modern applications should combine solar + battery to reduce peak export and improve the DNO's assessment. This can unlock a connection where a solar-only application would have been offered a large reinforcement bill.
Get help with a G99 or G100 application
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