Germany’s energy transition involves the accelerated phase-out of conventional power plants, which leads to a decline in system inertia. Although large battery storage systems (BSS) are usually the focus of ancillary service investigations, a significant untapped resource lies in the almost 2 million small-scale BSS installed behind the meter in prosumer households. Residential BSS represent the largest share of the BSS market in Germany. These distributed assets could provide inertia alongside their primary application self-consumption increase (SCI), either exclusively (Single-Use) or concurrently with market and system services (Multi-Use).

This paper investigates how the provision of inertia would influence the operational behaviour of residential BSS. The impact is analysed by taking the key figures such as the equivalent full cycles (EFC), self-consumption quota (SCQ) and self-sufficiency quota (SSQ) into account, as well as the economic performance and the general behaviour of the BSS, examining the power flows of the prosumer household. A mathematical optimisation model, developed at the elenia Institute as part of a research project, is expanded by inertia power and energy reservation considering the lately released German market based procurement concept. The simulations are carried out for different marketed inertia amounts, also varying in asymmetric and symmetric marketing, varied household and photovoltaic profiles and operation strategies as well as different component configurations, considering a prosumer household consisting of a PV, BSS and optionally an electric vehicle and/or a heat pump.

Preliminary results indicate that allocating power for inertia provision up to 50% of the rated power in Single-Use Operation of SCI has neglectable impact on the EFC, the SCQ and the SSQ, as the charging and discharging processes can be shifted within the PV production and load times. An overload capability of a BSS leads to less impact in the operation, as the overload power can be exclusively used for inertia without affecting charging and discharging with the rated power.

The in-depth analysis of how inertia provision affects the operation of residential BSS enables the formulation of practical recommendations on optimal installation configurations, market-participation strategies, and conclusions regarding the overall potential of residential BSS for offering inertia.