Long-duration energy storage could reduce fossil fuel generation on the all-island electricity system by more than 2TWh a year, according to a new study by Energy Storage Ireland and TNEI.
The report models a future power system with 9GW of onshore wind, 8GW of solar and 5GW of offshore wind to assess how storage deployment could strengthen grid performance and displace thermal generation.
Energy Storage Ireland said portfolios of eight-hour storage could cut fossil output by up to 1TWh annually. Deploying 100-hour duration assets across the network could double that impact to more than 2TWh per year.
Launching the report, Bobby Smith, director of Energy Storage Ireland, said fossil fuel generation is still projected to reach about 7.4TWh in 2035 under a high-renewables scenario.
He added that large-scale storage materially reduces this reliance.
“This represents a nearly 30% reduction in fossil fuel use within the power system and demonstrates the transformative role long-duration storage can play in a deeply decarbonised grid,” Smith said.
The study also found curtailed renewable energy reached roughly 1.72TWh in 2025 and could climb to 11TWh in a modelled 2035 system without further intervention.
Energy Storage Ireland said long-duration storage would significantly reduce this lost renewable output while lowering import costs and consumer bills.
Smith added that the findings reinforce the importance of extended-duration technologies in achieving Ireland’s climate and energy security goals.
