Key Technical Terms and Abbreviations Explained

Anyone dealing more intensively with battery energy storage systems (BESS) for the first time quickly realizes that, alongside technical, regulatory and economic questions, a wide range of abbreviations and specialist terms appear. In project discussions, quotations or profitability calculations, terms such as BESS, EMS, FTM or arbitrage are omnipresent—often without clear classification.

Especially in early project phases, a lack of terminological clarity can lead to misunderstandings or unrealistic expectations. The “BESS jungle” is dense—and difficult to navigate without orientation.

The aim of this article is therefore to classify key practical terms concisely and explain them in a clear and accessible way. The basis is the glossary from our checklist, which systematically summarizes the most important abbreviations and concepts related to battery storage systems.

Context: Where does this variety of terms come from?

Battery energy storage systems sit at the intersection of power generation, grids, consumption and electricity markets. As a result, different disciplines converge: electrical engineering, energy economics, regulation and IT. Each of these perspectives brings its own terminology, which then blends together in day‑to‑day project work.

In addition, BESS are highly flexible—both technically and economically. This versatility is directly reflected in the terminology used.

Core terms related to battery energy storage systems

Storage system types & operating models

BESS

Classification: Battery Energy Storage System

Meaning: Large‑scale battery storage system

Co‑located storage (Co-Located- Speicher)

Classification: Storage system located at the same site as, for example, a PV plant

Meaning: Both grey power and green power storage are possible. Used to optimize self‑consumption or reduce local grid congestion. Optimization of PV revenues.

FTM

Classification: Front of the Meter

Meaning: Battery storage system installed on the grid side—between the grid connection point and consumption/generation.

Grey power storage (Graustromspeicher)

Classification: Charging with grid electricity of unknown origin (energy mix)

Meaning: No green attribute; may have implications for levies and charges.

Green power storage (Grünstrom- Speicher)

Classification: Battery charged exclusively with renewable electricity

Meaning: Meets requirements for EEG accounting, often eligible for funding and regulatorily advantageous

Multi‑use / mixed storage (Multiuse-/ Mixed-Speicher)

Classification: Co‑located storage used for both green and grey electricity

Meaning: Storage system designed for multiple revenue streams and suitable both for self‑consumption optimization and for trading/marketing.

Peak-Shaving/ Spitzenlastkappung

Classification: Revenue generation option

Meaning: Reduction of capacity charges by capping peak loads ⇒ limiting maximum consumption.

Stand‑alone storage (Stand-Alone- Speicher)

Classification: Independent storage system without direct coupling to a generation asset

Meaning: Flexibly deployable for arbitrage and balancing services.

Technical components & systems

BMS

Classification: Battery Management System

Meaning: Control and monitoring unit for battery storage systems: monitors and protects the battery (cell voltage, temperature, overcharge, deep discharge) and ensures voltage balancing between cells.

BTM

Classification: Behind the Meter

Meaning: Storage system installed on the consumer side—directly behind the electricity meter.

EMS

Classification: Energy Management System

Meaning: Intelligent software and hardware control system: manages energy flows across the entire system, optimizes charging and discharging, maximizes self‑consumption and integrates the storage system into the overall setup (PV, wind, grid).

EZA

Classification: Controller for power generation assets

Meaning: Higher‑level control component and central interface to the grid operator: ensures grid‑compliant and regulation‑compliant operation, fulfills grid operator requirements (e.g. remote control) and enables direct marketing.

PCS

Classification: Power Conversion System / Inverter

Meaning: Converts direct current (DC) from the battery into alternating current (AC) and vice versa; ensures voltage, frequency, active/reactive power provision and grid support functions so that the storage system can interact correctly with the power grid.

Revenue models & applications

Arbitrage trading (Arbitrage-Handel)

Classification: Revenue generation option, day‑ahead or intraday

Meaning: Possible for both green and grey power storage. Electricity is purchased at times of low prices ⇒ battery charging; electricity is sold at times of high prices ⇒ battery discharging.

Atypical grid usage / peak load time windows (Atypische Netznutzung/ Hochlastzeitfenster)

Classification: Revenue generation option

Meaning: Grid relief and reduction of grid fees by shifting own load peaks to times outside peak load windows.

Self‑consumption (Eigenverbrauch)

Classification: Revenue generation option

Meaning: Storage of surplus, low‑cost energy for later on‑site consumption.

Betrieb & Marktrollen

GU/ EPC

Classification: General contractor / Engineering, Procurement and Construction

Meaning: A single contractor is responsible for all project phases. The client receives a turnkey, operational asset or facility.

O&M

Classification: Operation & Maintenance

Meaning: Operation, maintenance and asset management.

Marketer (Vermarkter)

Classification: Direct marketer

Meaning: Interface between plant operators and the electricity market: purchases surplus electricity and markets it on the power exchange.