​Terna is holding a consultation on new rules for the 2028 capacity auction in Italy. The new proposal reduces de-rating coefficients for all battery durations, driven by projections of 4 GW of additional batteries in the North and 64 GW of solar nationwide. The consultation is open until March 9, 2026.

Key takeaways

• 4-hour batteries—the most common in Italy’s capacity market—fall from 67% of nameplate to 53%, representing a 21% drop in qualified capacity (Methodology, points 16-17). All battery durations face a 20-25% reduction.
• Italy currently offers the most generous battery de-rating in Europe. The proposed changes would put Italian batteries below Belgium and closer to Great Britain for 4-hour systems.
• Lower de-rating reduces the total qualified capacity of the existing battery fleet, widening the gap between supply and demand and supporting higher clearing prices. Overall, the de-rating cut outweighs the clearing price impact for batteries.
• A new bidding floor (Art. 24.2b) requires existing operators to offer their full capacity from the first session, tightening auction strategies together with the 4% price-step rule (Art. 24.9).

The proposal reduces battery qualification across all durations

Italy’s de-rating coefficients determine how much of a battery’s nameplate capacity counts as firm capacity. Currently, a 4-hour system qualifies at 67% of nameplate.

With the new proposal, this drops to 53%, so a 100 MW project would secure only 53 MW instead of 67 MW. Shorter durations face even larger cuts: 1-hour batteries fall from 24% to 18%, and 8-hour batteries from 90% to 69%.

The reduction reflects a risk of saturation. As the battery fleet expands, Terna expects batteries to discharge at the same time during stress events, so each additional MW contributes less to system reliability.

These coefficients apply specifically to the 2028 auction and will be recalculated for future auctions as the fleet evolves.

Italy’s proposed de-rating would put batteries below most European peers

Italy currently leads Europe in BESS de-rating.

But the new proposal changes this: at 53%, a 4-hour battery would fall below Belgium, and the gap with Great Britain widens for longer durations.

De-rating methods vary widely across markets, but overall, Italy is moving from the top of the European scale toward the middle.

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The supply curve shifts twice: less qualified capacity, more zero-price bids

​The de-rating reduction has a double effect. Each battery qualifies for fewer MW, but the total qualified capacity of the existing fleet also shrinks. If Terna keeps the same adequacy target, the supply-demand gap widens, creating more room in the auction for new entrants, and clearing prices are likely to rise.