Grid congestion is congestion on the electricity network: at a given moment, more power is being drawn from or fed into an area than the cables and transformers can carry. The network operator then cannot offer new or larger connections until the network has been reinforced.
Two directions
- Demand congestion — too much simultaneous consumption. It affects industrial estates, charging hubs, heat pumps and data centres. The consequence is waiting lists for new connections and for upgrades to existing ones
- Export congestion — too much simultaneous generation, particularly on sunny afternoons where a street is full of solar panels. Network voltage rises
What a householder notices
For domestic customers the constraint is usually on export. Nominal low-voltage supply in most of Europe is 230 V, with a permitted band under EN 50160 of roughly 207 to 253 V. When many inverters in one area export at once, voltage rises at the far end of the cable. Above the upper limit an inverter shuts itself down — not a fault, but a mandatory protective function that safeguards other appliances. The result is that the system produces nothing at precisely the sunniest moment.
What helps
- Get it measured. Network operators will log voltage over several days on request. If voltage is persistently high, the network is at fault rather than your installation
- Check the cable between inverter and consumer unit. An undersized or over-long run adds voltage drop — and therefore voltage rise when exporting. A larger conductor or a shorter route often solves a great deal
- Spread the inverter across phases on a three-phase supply instead of loading one phase
- Use more of your own generation as it happens: charge, wash, heat water or run the heat pump during the day
- Battery storage or managed export can shave the peak; work through the economics before committing
- Businesses should look at flexible connection agreements and at coordinating with neighbours on the same feeder
Points to watch
- Apply for a large connection early. Lead times in congested areas run into years; build that into the programme
- Check the connection position with the network operator before buying a site, especially for commercial development
- Choose the connection capacity deliberately. A larger connection carries a standing charge; too small means queueing again later
Related terms
- Central heating boiler
- Energy label
- Back-up heating for a solar water heater
- Ecological building
- Green roof
- Planning permission
Want to know more about building terms? Visit our knowledge base at fredsdiyplans.com.