Clean Power 2030 metrics

Now I have everything I need. Here's the memo:

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What the numbers show

DESNZ's first Clean Power 2030 scorecard reports two metrics that tell different stories. The generation share — clean sources as a proportion of total GB generation (excluding EfW and CHP) — reached 73.3% in 2025, marginally down from 73.7% in 2024. The demand share — clean generation as a proportion of qualifying GB demand — stood at 64.4% in 2025, up from 63.7% in 2024.

The gap between these two numbers is the scorecard's most important feature. In 2025, GB generated 171.9 TWh of clean power but qualifying demand was 266.9 TWh. Clean sources covered less than two-thirds of what the country actually consumed.

Within the generation mix, renewables (excluding EfW and CHP) rose to 136.1 TWh in 2025, up from 128.4 TWh in 2024 — a 6% year-on-year increase. Nuclear moved sharply the other way: 35.9 TWh, down from 40.6 TWh, reflecting ongoing outages and the approaching end of life for AGR stations. Fossil fuel generation (excluding CHP) ticked up to 61.9 TWh from 59.6 TWh, filling the gap left by nuclear.

Emissions intensity fell to an estimated 104 gCO2/kWh in 2025, down from 107 in 2024 and a record low. But the 2025 figure relies on estimated emission factors carried forward from 2024 — the actual number will be revised.

Total GB demand was essentially flat at 311 TWh, showing no sign of the electrification-driven demand growth that underpins most Net Zero scenarios.

Trends

The six-year series (2020–2025) shows three clear patterns.

Renewables are doing the heavy lifting. Clean generation has grown from 169 TWh in 2020 to 172 TWh in 2025, but almost all of that growth is renewables (119 TWh → 136 TWh). Nuclear has declined from 50 TWh to 36 TWh over the same period. The clean generation total has barely moved because renewable gains are being offset by nuclear losses.

The generation-demand gap is structural. In every year, the generation share exceeds the demand share by 5–9 percentage points. This gap represents curtailment, exports, and transmission losses — clean electrons that are generated but do not serve GB demand. In 2025, roughly 9 percentage points of clean generation did not translate into clean supply. This is not a temporary problem. It reflects the mismatch between where renewables generate (Scotland, offshore) and where demand sits (England, South East).

Fossil fuel generation has a floor. Gas generation dropped from 98 TWh (2022) to 60 TWh (2024) but then rose to 62 TWh in 2025. Without new dispatchable clean capacity, gas remains the system balancer. The floor is set by peak demand, wind droughts, and nuclear availability — not by how many turbines are installed.

Demand is flat. 311 TWh in 2025 versus 319 TWh in 2020. The electrification of heat and transport that is supposed to increase demand has not materialised in aggregate numbers. If demand does grow as projected, the 95% clean generation target becomes harder, not easier, because the denominator expands.

What to watch

The 95% target is a generation metric, not a demand metric. DESNZ defines Clean Power 2030 as clean sources producing "at least 95% of Great Britain's generation." At 73.3% in 2025, the system needs to gain roughly 22 percentage points in five years. That requires both a step-change in clean capacity and a steep decline in gas generation — which in turn requires either massive storage deployment or firm clean capacity that does not yet exist at scale.

Nuclear decline is the hidden headwind. Losing 14 TWh of nuclear output since 2020 means renewables have to run harder just to stand still. Hunterston B and Hinkley Point B are closed. Torness and Heysham are in life extension. Each closure accelerates the problem. Hinkley Point C's delays matter more in this context — every year it slips is another year where gas fills the nuclear gap.

The demand share is the metric that matters commercially. A generator cares about the generation share. A consumer, an industrial user, a data centre developer — they care about whether clean power actually meets demand. At 64.4%, GB is not close. The constraint is not generation capacity but grid capacity, storage, and the ability to deliver clean power to where it is consumed.

Note 6 in the spreadsheet is worth flagging: 2025 emissions figures are estimated, not measured. The 104 gCO2/kWh headline will be revised when actual data is available. If gas ran harder than the estimate assumes, the true figure will be higher.