Basic Variable Operations and Maintenance (O&M)

Usage impacted costs associated with non-fuel consumables necessary to operate the storage system throughout its economic life.

Calendar Life

The maximum life of the system, regardless of operating conditions. For batteries, calendar life depends on the ambient temperature and state of charge (SOC).

Controls and Communication

Includes the energy management system for the entire ESS and is responsible for ESS operation. May also include annual licensing costs for software; typically represented as a fixed cost scalable with respect to power and independent of duration.

Cycle Life

The cycle life for an ESS is a function of depth of discharge and measures the total number of cycles that an ESS can provide over its life.

Disassembly/Removal

Deconstruction of ESS and components for disposal or recycling

Disconnection

Costs associated with the removal of ESS interconnection from grid.

Duration Corresponding to Cycle Life

Calculated by dividing the cycle life by the number of cycles per year, accounting for downtime.

Engineering Procurement and Construction (EPC)

Includes non-recurring engineering costs, construction equipment, and shipping, siting and installation, and commissioning of the ESS; cost is weighted based on E/P ratio.

Grid Integration

Direct cost associated with connecting the ESS to the grid, including transformer, metering, and isolation breakers. For the last component, it could be a single disconnect breaker or a breaker bay for larger systems.

Insurance

Insurance fees to hold a policy to cover unknown and/or unexpected risks. Terms of this cost may depend on vendor reputation and financial strength.

Power Equipment

Bi-directional invertor, DC-DC converter, isolation protection, alternating current (AC) breakers, relays, communication interface, and software. This is the power conversion system for batteries, the powerhouse for PSH, and the power island/powertrain for CAES.

Project Development

Costs associated with permitting, power purchase agreements, interconnection agreements, site control, and financing

Recycle/Disposal

Cost associated with separating out recyclable components, shipping to recycling plant, and recycling the material in the plant

Response Time/Ramp Rate

The time for an ESS to go from 0 to 100% rated power

Round Trip Efficiency (RTE)

The ratio of net energy that is discharged to the grid (after removing auxiliary load consumption) to the total energy used to charge the ESS (after including the auxiliary load consumption). 

​​​​*Note: RTE for any technology depends on operating conditions.

 RTE Losses

Includes HVAC and other auxiliary loads, DC losses, power conversion system losses

Site Remediation

Costs required to return site to either Brownfield or Greenfield state

Storage - Balance of System (SBOS)

Includes supporting cost components for the storage block with container, cabling, switchgear, flow battery pumps, and HVAC.

Storage Block

Component includes the price for the most basic DC storage element in an ESS (e.g., for lithium-ion, this price includes the battery module, rack, and battery management system, and it is comparable to an electric vehicle (EV) pack price).

Storage System

​​​​​​​The sum of the SB and SBOS costs and an appropriate level of granularity for some studies.

System Integration

​​​​​​​Price charged by the system integrator to integrate sub-components of a BESS into a single functional system. Tasks include procurement and shipment to the site of battery modules, racks with cables in place, containers, and power equipment. At the site, the modules and racks are containerized with HVAC and fire suppression installed and integrated with the power equipment to provide a turnkey system.

Warranty

Fees to the equipment provider for manufacturability and performance assurance over designated lifespan