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Carnot batteries: Economics

Paper costs that beat batteries, still waiting for proof

What this tab covers Economics and financial structure: capital versus operating cost, levelised cost of storage, and how the asset earns money.

Modelled costs for long durations look competitive with batteries, but no plant has proven them, and the low efficiency makes revenue sensitive to the gap between charging and selling prices.

Capex versus opex

Mixed

Published estimates span a wide range: USD 2,000 to 4,000 per kW and USD 50 to 1,500 per kWh for Brayton systems. One 7.6 MW, 80 MWh project was costed at about EUR 200 to 250 per kWh, against about EUR 450 per kWh for a German lithium-ion project; Malta targets under USD 100 per kWh at full scale. There are no cell or stack replacements; the main maintenance is the turbomachinery.12

Brayton PTES capex USD 2,000-4,000 per kW; 50-1,500 per kWh1 OPTES 80 MWh estimate EUR 200-250 per kWh2 Malta target (company claim) under USD 100 per kWh2

Levelised cost of storage

Mixed

Reviewed averages are about USD 230 per MWh for Rankine PTES and USD 369 for Brayton. NLR's newer silica-particle model gives USD 115 per MWh, plus or minus 30, for 10-hour discharge, against USD 171 for molten salt, and its reference nitrogen cycle gave USD 135 per MWh with power bought at USD 25 per MWh. Lazard's 2026 range for a 4-hour lithium battery is USD 210 to 292 per MWh, so on modelled numbers PTES looks competitive at 10 hours or more, but no plant has yet proven these costs.1345

Reviewed LCOS, Rankine / Brayton about USD 230 / 369 per MWh1 NLR silica PTES, 10 h (modelled, 2025) USD 115 plus or minus 30 per MWh3 Lithium-ion 4-hour LCOS (2026) USD 210-292 per MWh5

Revenue stack and market participation

Mixed

Best suited to daily or multi-day arbitrage and capacity payments, where 10 hours or more are valued. Because it discharges through spinning generators, it can provide inertia and voltage support like a conventional plant. Selling low-grade heat helps: NLR's design rejects 75 MW of heat at about 117 C that could serve industry or district heating. Coal-site conversions can reuse existing grid connections.14

Heat rejected, NLR 100 MW design 75 MWt at 116.7 C4

Sources

  1. Carnot Battery development: A review on system performance, applications and commercial state-of-the-art (Vecchi et al., Journal of Energy Storage 55, 105782) University of Birmingham repository, 2022
  2. Review of Carnot Battery Technology Commercial Development (Novotny et al., Energies 15(2), 647) MDPI, 2022
  3. Advancing Pumped Thermal Energy Storage Performance and Cost Using Silica Storage Media (Applied Energy 387, 125567) National Laboratory of the Rockies (formerly NREL), 2025
  4. Design-Point Techno-Economics of Brayton Cycle PTES for Combined Heat and Power (Neises and McTigue, GTP-24-1410) NREL (now National Laboratory of the Rockies) / OSTI, 2024
  5. Lazard's Levelized Cost of Energy+ (LCOE+), July 2026 (LCOS) Lazard, 2026