How loaded the distribution network actually is, and where it is heading. Published headroom says what a network can accept; utilisation shows how hard its transformers already work.
| Primary substation | Transformer | Grid supply point | Area | Peak, prior 12 months | Peak, latest 12 months | Change |
|---|
| Substation | Area | Headroom | Winter peak | Growth a year | Years | Runway |
|---|
UK Power Networks publishes monthly peak, percentile and mean load for every primary and grid transformer, updated daily. SP Energy Networks publishes each transformer’s annual peak alongside its firm capacity for 2013 to 2024. Northern Powergrid publishes distribution transformer utilisation for 2025 with forecasts to 2050/51. Electricity North West and SSEN publish nothing comparable. NGED’s historic transformer flows end in 2021 and its live feed holds only a few days, so NGED is not shown. SSEN Distribution and NGED are not shown: Strata reads no transformer-level utilisation dataset from either. SSEN’s smart meter feeder data covers low-voltage circuits only and is not used.
Grid supply point: the substation where the national transmission network (400 and 275 kV) hands power to the regional distribution network (132 and 33 kV). Each primary substation is fed from one, and its limit can cap what the substations beneath it can take. SP Energy Networks does not publish the grid supply point for its Merseyside and North Wales transformers, so those rows show “Not published”. Firm capacity: the load a substation can carry with its largest transformer out of service. Forecast: Northern Powergrid’s own projection of transformer loading; Azraq does not adjust it.
The three networks measure different things and should not be compared directly. UK Power Networks’ trend is an index of peak current, because the dataset carries no firm capacity; the mix of reporting transformers changes slightly month to month. SP Energy Networks covers primary substations. Northern Powergrid covers the smaller distribution transformers closer to customers, where forecast demand from heat pumps and vehicle charging drives the growth.
Each UK Power Networks transformer’s highest monthly peak current in the latest 12 months is compared with the 12 months before. Transformers with a prior peak under 50 A are excluded, so small absolute changes do not dominate the ranking. The largest jumps usually reflect load transferred from a neighbouring substation during works or reconfiguration, not new demand.