GB clean spark spreads fall 90% from highs, though remain elevated

During 2022, month ahead GB clean spark spreads (CSS, a measure of gas power plant profitability) peaked at around £280/MWh and £610/MWh in base and peak power respectively. The sharp decline vs seasonal average European power demand (driven by warmer weather and response to high prices) along with lower gas prices and an improved European nuclear outlook has reduced month ahead CSS to £16/MWh for base and £46/MWh for peak.

Baseload CSS forward prices are structurally negative from summer 2026 onwards indicating falling load factors for less efficient plants as renewables increasingly push them to the margin. As more and more wind and solar capacity comes onto the system, baseload CSS are pricing lower than the current market, which is still high vs historical standards (e.g. pre-2021 PK CSS levels of ~£4-10/MWh).