Solar export limits in the UK 2026 — when the DNO becomes the binding constraint

Solar export consent — how much solar generation a DNO will accept onto the network at a given site — has become the binding constraint on commercial solar sizing for an increasing share of UK projects. Industrial estates with constrained grid headroom (Black Country, parts of Greater Manchester, parts of Yorkshire) are seeing 25-40% of new commercial solar applications hitting export-consent issues that materially affect project sizing.

The UK DNO export consent landscape

UK DNOs (UK Power Networks, Northern Powergrid, SP Energy Networks, Western Power Distribution, Electricity North West, SSEN) operate G99 connection processes for generation above 16A per phase. The thresholds and process steps:

• Below 50 kWp: G98 connection, installer-self-certifies, fast-track process. Typical 4–8 weeks DNO-side.
• 50 kWp – 200 kWp: G99 connection but no formal study required in most cases. Typical 6–12 weeks DNO-side.
• 200 kWp – 500 kWp: G99 connection requires connection study. Connection cost £3k–£8k typical. Reinforcement charges possible on grid-constrained sites £5k–£25k.
• 500 kWp – 1 MWp: G99 connection with full network impact assessment. AVR studies frequently triggered. Reinforcement charges range £10k–£60k depending on site grid context.
• Above 1 MWp: G99 connection often triggers substantive reinforcement — dedicated transformer £40k–£80k, AVR £15k–£30k, network upgrade £30k–£100k.

When the DNO becomes the binding constraint

Three scenarios where DNO consent dominates project sizing:

Constrained grid headroom. Older industrial estates have substantial existing connection capacity but limited headroom for additional generation. The DNO grants partial export consent (e.g. 200kWp consent on a 500kWp solar request) or zero export consent ("export-curtailed"). The site can install the full solar capacity but generation above the export limit is curtailed.

Reinforcement cost making project uneconomic. Where DNO reinforcement requirement adds £50k+ to project cost, the economics may not support the larger solar size. Some projects size down to avoid triggering reinforcement.

Long DNO timelines. On constrained networks, reinforcement studies and execution can take 12–24 months. Projects with year-end FYA capture timing pressure may need to size below the reinforcement threshold to fit the available timeline.

Four strategies for constrained connections

1. Size below the constraint threshold

   Most direct response. Where DNO grants 200kWp export consent on a 500kWp request, accept 200kWp as the project size. Lose the additional 300kWp of capacity but avoid the reinforcement cost and timeline.

2. Battery storage to absorb curtailed generation

   Where DNO grants full export consent but practical export is curtailed by network conditions, battery captures the would-be-curtailed energy for later self-consumption. Adds £400/kWh capex but recovers value otherwise lost. Discussed in our battery storage finance page.

3. Self-consumption-only design

   Where export consent is zero or impractical, design the solar system specifically for 100% self-consumption — sized below daytime demand floor, never producing surplus to export. Limits installable capacity but avoids consent friction. Suits sites with very high continuous demand.

4. Pay for reinforcement

   Where larger system economics support reinforcement cost (£50k–£200k typical), accept the cost and timeline as part of project capex. Common on >1 MWp projects where reinforcement supports system that wouldn't fit otherwise.

DNO engagement timing

Engage the DNO early in project development — ideally at concept stage rather than after design completion. The connection study identifies constraints before they become problems:

• Pre-application engagement: Most DNOs offer informal pre-application advice on likely constraints at a candidate site. 2–4 week response time. Worth the conversation before full project commitment.
• Connection study application: Submit at concept stage to confirm available headroom and identify reinforcement needs. £2k–£8k cost depending on size.
• Connection offer review: When DNO issues connection offer, review carefully. Some terms (export curtailment, AVR fitting, reinforcement charging) are negotiable; others fixed by network conditions.
• Reinforcement timing: Where reinforcement is required, agree timeline early. Some networks allow generator-funded acceleration of reinforcement at additional cost.

Where DNO constraints are most pressing in 2026

Geographies with active DNO constraint pressure on commercial solar in 2026:

• Black Country industrial estates — historic industrial connections substantial but constrained for additional generation
• Parts of Greater Manchester — Trafford Park, Wythenshawe, Bolton with partial constraint pressure
• South Yorkshire industrial corridors — Sheffield-Rotherham-Doncaster axis
• South Wales steel/chemical clusters — Port Talbot adjacent and Newport semiconductor
• Some Hertfordshire / Essex commercial parks — particularly mature business parks with high existing tenant load

Geographies with generally cleaner DNO position: M1/M6/M62 mega-warehouse corridors (purpose-built capacity), newer industrial estates (Wakefield Europort, DIRFT, Magna Park), and Energy Estuary infrastructure (Humber, Liverpool docks). DNO position is highly site-specific even within these regions.