Capacitors and supercapacitors: Economics
Pricey per kWh, competitive when cycled dozens of times daily
What this tab covers Economics and financial structure: capital versus operating cost, levelised cost of storage, and how the asset earns money.Per kWh supercapacitors are among the most expensive storage on the market; per kW and per cycle they can be competitive where a system cycles dozens of times a day for fast grid services.
Capex versus opex
MixedDOE's 2025 baseline for a 1 MW, 45-second EDLC plant adds up to roughly USD 54,000 per kWh, or about USD 880 per kW once power electronics and grid connection are included (calculated from its cost table). Some non-cell costs were borrowed from lead-acid estimates for lack of data. Operating costs are tiny (USD 1 per kW-year fixed) and, with a million-cycle life, cells are rarely replaced.3
Installed cost (calculated sum of DOE components) about USD 54,000/kWh; about USD 880/kW3 Fixed O&M USD 1/kW-year3Levelised cost of storage
UnfavourableDOE puts the baseline levelised cost at USD 0.443 per kWh per cycle (about USD 443 per MWh of rated energy cycled) assuming 40 cycles a day, falling to about USD 0.11 at 160 cycles a day. The best R&D portfolios would cut the baseline by 23 to 26%. This is far above long-duration batteries on a per-MWh basis, which is why supercapacitors are judged on power services, not energy shifting.3
LCOS baseline (2025 estimate, 45 s, 40 cycles/day) USD 0.443/kWh-cycle3 LCOS at 160 cycles/day USD 0.11/kWh-cycle3 Potential reduction from R&D 23 to 26%3Revenue stack and market participation
MixedSupercapacitors earn from services lasting seconds: fast frequency response, synthetic inertia, voltage support, ride-through until backup generators start, wind turbine pitch control and braking energy recovery on trams. DOE notes that regulation markets measured over 15 minutes undervalue them; settlement periods under 5 minutes would help. Ancillary services are a thin pool, historically under 5% of US wholesale market value. DOE cites a market of about USD 1.5 billion in 2021 and a forecast of USD 15 billion by 2030 (a 30% annual growth rate). Tesla bought Maxwell, a leading maker, in 2019 and sold the ultracapacitor business on in 2021, a sign of how niche the segment is.367
Global market (2021) USD 1.5 billion3 Forecast market (2030) USD 15 billion3 Ancillary services share of US wholesale market value under 5%7 Tesla purchase of Maxwell (2019), as reported in trade press about USD 235 million in Tesla shares; ultracapacitor unit sold to UCAP Power in 20216Sources
- Technology Strategy Assessment: Supercapacitors (Energy Storage Grand Challenge, #10) US Department of Energy, Office of Electricity, 2023
- Tesla sells back Maxwell Technologies ultracapacitor business to former executives (trade press) Electrek, 2021
- Pathways to Commercial Liftoff: Virtual Power Plants US Department of Energy, 2023