The apparent gap between clean energy (64–65%), fossil gas (27–32%), and 100% reflects a fundamental difference in how electricity statistics are reported. Domestic generation shares do not account for cross-border electricity flows, which are material to the UK's actual supply mix.

Net imports via subsea interconnectors from France, Norway, Belgium, and the Netherlands are the dominant component of the remainder. One member cited approximately 10–12% of total electricity supply coming from net imports in 2025, with imports rising to around 15% during peak winter demand periods [1][2]. This is a significant contributor that is often omitted from generation-focused breakdowns but is essential to understanding total supply delivered to consumers.

Smaller components include electricity storage (battery and pumped hydro systems), which contributed a growing but modest share—estimated at 1–2% of the mix in 2025 as grid flexibility increased to manage intermittent renewables [3]. Rounding differences and minor fuel categories (oil-fired backup, miscellaneous sources) account for the final fraction. Biomass or bioenergy contributions vary by dataset and accounting method, making a single precise figure unreliable across sources.

The core issue is that when reports state "65% low-carbon and 32% fossil gas," they typically refer to domestic generation only. Total electricity supply to consumers includes imports, which bridge the gap to 100%. Different sources measure either generation (domestic production) or supply (what consumers actually receive), creating apparent arithmetic inconsistencies. Using a single consistent data source—such as DESNZ annual generation tables or NESO's 2025 review—would resolve these variations, but across multiple official datasets, net imports remain the primary explanation for the remainder [1][3][4].