The short answer
Commercial applications typically:
- Have bigger systems (25 kW+)
- Sit on more complex parts of the network (three-phase supplies, closer to substations)
- Trigger a full network study rather than a desk review
- Get assigned to different (fewer) engineers than the domestic queue
The five main reasons
1. Larger export = network impact study
Higher export figures trigger extra checks on voltage, thermal capacity, and fault levels of the local network.
2. Three-phase adds complexity
Most domestic G99s are single-phase. Three-phase commercial requires phase balance checks and different protection settings.
3. Different queue, fewer engineers
DNOs often route commercial applications to a smaller team of senior engineers. That team is a bottleneck.
4. More stakeholders
On a big job, the DNO may consult with National Grid, transmission operators, or neighbouring DNOs. Each consultation adds time.
5. Reinforcement quotes
When the local network needs upgrading (new transformer, cable upgrade), the DNO must produce a connection offer with a price. That can be a lengthy piece of work in its own right.
Setting customer expectations
We won't quote specific week counts because commercial timelines vary hugely by DNO, system size, and network location. If you need a rough steer for a particular job, ask us and we'll tell you what we're currently seeing.
[!TIP] For commercial jobs, get the application in as early as possible. Ideally before the customer signs the contract, so timelines don't kill the deal.
What speeds things up
- Clean, complete submission (no RFIs)
- Choosing standard, well-known inverter brands
- Accepting reasonable export limits upfront rather than negotiating
- Working with someone who chases the DNO on a proper cadence (we do this)