​A 10% Capex overrun on a battery built today costs about 2 percentage points of unlevered IRR. Knowing what you should be paying is critical for any business case, but reliable Capex benchmarking data is hard to get.

That is why Modo Energy has surveyed over 100 investors, developers, EPCs and OEMs across 20 markets. The results have been fed back into our modelling to update how much storage is built across markets and what that means for revenue levels.

Key takeaways

• ​Globally, total Capex for two-hour projects averaged US$325k/MWh. Four-hour projects cost US$201k/MWh.
• Capex has fallen since 2024. In Great Britain (GB), two-hour Capex is now 29% lower than 2 years ago. Most of that decline sits in the containerised BESS.
• The duration premium narrowed, from 38% according to Modo Energy’s 2024 data to 22% between 2- and 4-hour durations.
• Capex aligns across regions. Containerised BESS costs, the largest Capex item, are globally standardised. Differences in grid connection costs explain a large share of differences across markets.
• The US is an outlier at the higher end of the stack, with Capex 15% higher than the global 2-hour average. That premium is due to import tariffs on containerised BESS units and subsidies that reduce the effective cost for developers.

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Total 2-hour Capex averages US$325k/MWh and US$660k/MW

Across geographies, median 2-hour Capex is US$325k/MWh and US$201k/MWh for 4-hour assets. Doubling duration cuts 38% per MWh.

Numbers are medians rather than means to account for outlier projects. The four-hour mean is 11% higher than the median.