Glossary

Key terms around energy management, storage and the German energy market – explained briefly. As of October 2026. These explanations are not legal advice.

§ 14a EnWG (controllable consumer devices)

German rule for controllable devices such as heat pumps, wall boxes and storage. Since 2024, grid operators may temporarily limit new devices to no less than 4.2 kW when the grid is at risk of overload. In return, grid charges are reduced – as a flat rate, a percentage or through time-variable grid charges.

AgNes (grid charge reform)

Short for “Allgemeine Netzentgeltsystematik Strom”, the German Federal Network Agency’s process to restructure electricity grid charges. Topics include more capacity-based pricing and having generators contribute to grid costs.

Arbitrage

A battery charges when electricity is cheap and discharges when it is expensive, turning price differences on the power market into revenue – especially with dynamic tariffs or direct marketing.

Atypical grid usage

Individual grid charge under § 19 StromNEV for customers whose peak load falls outside the grid operator’s high-load time windows. Grid charges can drop to as little as 20 % – storage and load shifting help meet the conditions.

Balancing energy

Energy the transmission system operator uses to offset deviations between forecast and actual consumption or generation in a balancing group. It is billed to the balance responsible party and can be very expensive.

Balancing group

A virtual energy account in which feed-in and consumption must balance for every quarter hour. The transmission system operator covers deviations with balancing energy and bills the balance responsible party.

Balancing reserve

Capacity that transmission system operators use to keep grid frequency at 50 hertz – as FCR, aFRR and mFRR. Prequalified storage can earn revenue from it.

Battery energy storage system (BESS)

Stationary storage made of battery modules, inverters and controls. It increases self-consumption, shaves load peaks, trades on the power market or supports the grid – often several of these at once.

Behind the meter

Assets behind a customer’s grid connection meter, such as solar, storage or wall boxes. They primarily serve the site itself, for example for self-consumption and peak shaving.

Capacity price

Part of grid charges for customers with load metering, billed per kilowatt of the highest quarter-hour load in the year. A single peak can therefore set costs for the entire year.

Co-location

Storage and a generation plant, such as a solar park and battery, share one grid connection. This saves connection costs and allows generation peaks to be stored.

CO₂ price

Price for emitting one tonne of CO₂ – in the EU Emissions Trading System for power plants and industry, and nationally in Germany for heating and transport fuels. It makes fossil energy more expensive and efficiency more economical.

Data governance

Rules, roles and processes defining who owns data, who may maintain it and what quality it must have. In energy companies it turns grid, metering and customer data into a reliable foundation.

Day-ahead market

Exchange auction in which electricity is traded for every quarter hour of the following day. Its prices are the basis for dynamic tariffs and storage schedules.

Default supply

The supplier with the most household customers in a grid area must supply every household there at standard prices. Anyone without their own contract automatically falls into default supply.

Demand response

Consumers adjust their power consumption to price or grid signals, for example by shifting processes or using storage. This lowers costs and relieves the grid.

Direct marketing

Renewable plants sell their power on the exchange through a direct marketer instead of receiving a fixed feed-in tariff. It is mandatory from 100 kW; plants additionally receive the market premium under the EEG.

Distribution system operator (DSO)

Operators of regional low-, medium- and high-voltage grids – more than 800 companies in Germany, often municipal utilities. They connect assets, operate meters and implement § 14a EnWG.

Dynamic electricity tariff

The energy price follows exchange prices and changes over the day. Since 2025, all German electricity suppliers must offer such a tariff; a smart metering system is required.

EEG (Renewable Energy Sources Act)

Germany’s Renewable Energy Sources Act supports solar, wind and biomass plants through feed-in tariffs or a market premium and governs their grid connection.

Electricity tax

Excise tax on electricity drawn from the grid. There are reductions, for example for manufacturing, and exemptions for power from smaller plants consumed on site.

Energy contracting

A service provider plans, finances and operates an energy asset – such as solar, storage or heating – at the customer’s site. The customer pays for the energy or service delivered instead of the investment.

Energy data management (EDM)

Collecting, validating, storing and providing meter readings and time series. An EDM is the data foundation for billing, balancing and analytics.

Energy management system (EMS)

Software that measures and actively controls a site’s generators, storage and loads based on prices, forecasts and grid requirements. Unlike pure monitoring, an EMS takes action itself.

Energy service provider (ESA)

Market role in German market communication: with the customer’s consent, an ESA receives readings from the smart metering system to build services such as energy management on them. Apollo is registered as an ESA.

EnWG (Energy Industry Act)

Germany’s Energy Industry Act is the legal framework for electricity and gas supply – from grid operation and grid charges to supplier obligations and consumer rights.

Feed-in tariff

Fixed payment per kilowatt hour fed in under the EEG, paid by the grid operator for 20 years. It applies to smaller plants; larger plants use direct marketing with a market premium.

Flexibility

The ability to shift generation or consumption in time – for example with storage, heat pumps or controllable processes. Flexibility can be monetised on the power market, for balancing or for grid services.

Forecast

Prediction of generation, consumption and prices, for example based on weather data and historical load profiles. Good forecasts underpin every storage and trading strategy.

Front of the meter

Assets connected directly to the grid and not assigned to a consumer – such as utility-scale batteries or solar parks. They earn revenue on the power market and from grid services.

Full-load hours

Annual energy divided by peak load. The value shows how evenly a site uses electricity and, with load metering, determines the grid charge tier.

Grid charge exemption for storage

Under § 118(6) EnWG, storage commissioned before August 2029 pays no grid charges for 20 years on electricity that is stored and fed back into the grid.

Grid charges

Fees for using the power grid and a major part of the electricity price. Depending on the customer group, they consist of an energy price, a capacity price and a standing charge, regulated by the Federal Network Agency.

Grid connection point

The point where an asset or site connects to the public grid. The grid operator’s technical requirements and the agreed connection capacity apply here.

Grid connection procedure

The process from the connection request through the grid operator’s assessment to approval and commissioning. For storage and larger plants it often determines schedule and profitability.

Grid location (NeLo)

Object in German market communication for grid-related values of a connection, for example to bill reactive energy. It complements market and metering locations.

Grid-supportive operation

Operating storage and loads in a way that relieves the grid – for example charging during high feed-in and discharging during high demand. Increasingly rewarded through grid charges.

Guarantee of origin (GO)

Electronic certificate proving that one megawatt hour was generated from renewable sources. In Germany, the Federal Environment Agency runs the registry; suppliers need GOs to label green power.

Intensive grid usage (baseload)

Individual grid charge for large consumers with at least 7,000 full-load hours and more than 10 GWh annual consumption at one site. Depending on the hours, grid charges drop to 20, 15 or 10 %.

Interval load metering (RLM)

Metering that records consumption and load in quarter-hour values. Mandatory from 100,000 kWh annual consumption; billing then uses an energy price and a capacity price.

Intraday trading

Continuous electricity trading for the current and next day until shortly before delivery. It is used to correct forecast deviations and capture short-term price peaks.

Inverter

Converts direct current from solar modules or batteries into grid-compliant alternating current. Modern inverters can be controlled via interfaces such as Modbus or SunSpec.

Load profile (metered)

Time series of actual consumption or generation, usually in quarter-hour values. It reveals peaks and patterns and is the basis for billing, optimisation and storage sizing.

Market communication (MaKo)

Standardised data exchange between grid operators, suppliers and metering point operators – for supplier switching, meter readings and balancing. The rules are set by the Federal Network Agency.

Market location (MaLo)

The point where electricity is generated or consumed and billed – the reference for supplier switching and balancing. Each market location has an 11-digit MaLo ID.

Market premium

Payment under the EEG for plants in direct marketing that covers the difference between the statutory value and the average market value of the power.

Master data

Fundamental, rarely changing data about assets, meters and sites – such as capacity, location, location IDs or controllability. Clean master data is a prerequisite for billing, redispatch and market communication.

Metering location (MeLo)

The point where energy is measured, i.e. the meter. A market location can consist of several metering locations; the MeLo ID has 33 characters and starts with “DE”.

Metering point operator (MSB)

Responsible for installing, operating and reading meters. This is usually the local grid operator by default, but customers can also appoint a competitive metering point operator.

MiSpeL (storage market integration)

Short for “Marktintegration von Speichern und Ladepunkten”, rules of the German Federal Network Agency that let storage charge both grid and renewable power without losing subsidies or levy relief. This works by separating the energy quantities through metering.

OCPP

Open Charge Point Protocol – an open standard for communication between charging stations and a backend. It allows chargers from different manufacturers to be monitored, billed and controlled in the same way.

Overbuilding the grid connection

The installed capacity of solar, wind or storage exceeds the connection capacity, and a controller limits feed-in. This makes better use of scarce grid connections.

Peak shaving

Reduces a site’s highest quarter-hour load, for example with storage or by shifting consumers. For commercial customers with load metering, this directly cuts grid charges, as the capacity price depends on that peak.

Plant controller (EZA controller)

Controller for generation plants that enforces the grid operator’s requirements at the grid connection point, such as active and reactive power or output limits. Mandatory for larger parks on the medium- and high-voltage grid.

Power exchange

Marketplace for electricity trading. In Europe, short-term trading takes place mainly on EPEX SPOT (day-ahead, intraday), futures on the EEX in Leipzig.

Power purchase agreement (PPA)

Long-term power supply contract directly between a generator and a buyer, often for wind or solar power. It gives both sides predictable prices for many years.

Reactive power

Power that oscillates between grid and devices without doing work. It is needed to maintain voltage; generation plants must provide it as specified by the grid operator.

Redispatch 2.0

Germany’s grid congestion management process: grid operators adjust the schedules of plants from 100 kW and of controllable plants in advance. Operators provide master data and forecasts and are compensated for curtailment.

Sector coupling

Linking electricity, heat and mobility – for example through heat pumps, electric vehicles or power-to-heat. Renewable power becomes usable in other sectors and creates flexibility.

Self-consumption

The share of self-generated power used on site instead of being fed into the grid. Storage and smart control increase it – usually the most economical use of solar power.

Shared building supply

Since 2024 (§ 42b EnWG), operators can share solar power with residents of the same building without taking on all obligations of an energy supplier. Residents keep buying their remaining power from their own supplier.

Smart meter gateway (SMGW)

BSI-certified communication unit of the smart metering system. It transmits encrypted readings to authorised market participants and enables control under § 14a EnWG.

Smart metering system (iMSys)

Digital meter with a smart meter gateway that transmits readings securely and can receive control signals. Mandatory in Germany, among others, from 6,000 kWh annual consumption, for solar systems from 7 kW and for § 14a devices.

Standard load profile (SLP)

Typical consumption curve for customers without load metering, such as households or small businesses. Grid operators and suppliers use it instead of actual quarter-hour values for balancing.

State of charge (SoC)

A battery’s charge level as a percentage of its usable capacity. The EMS plans the state of charge so that capacity is available for cheap charging times, load peaks or backup power.

Tenant electricity

Solar power from a building’s rooftop supplied directly to tenants, together with residual grid power. The provider takes on the obligations of an energy supplier and may receive a tenant electricity bonus.

Time-of-use tariff

Tariff with fixed price levels by time of day, such as cheaper night-time power. Unlike dynamic tariffs, prices are known in advance – easy to plan for storage and heat pumps.

Time-variable grid charges

Grid charges with high, standard and low rates by time of day, available since 2025 for § 14a devices with a smart metering system (module 3). Shifting consumption to cheaper times saves money.

Transmission system operator (TSO)

Operators of the extra-high-voltage grids – in Germany 50Hertz, Amprion, TenneT and TransnetBW. They are responsible for system stability, balancing reserve and settlement.

Virtual power plant (VPP)

Aggregation of many decentralised assets such as solar, storage and heat pumps that are controlled centrally and marketed together – like one large power plant.