How does energy storage work in a single-family home?

The growing importance of self-consumption of energy and changes in prosumer billing systems make energy storage a natural extension of photovoltaic installations in the residential sector.

In practice, however, it is not just a "battery for the house," but an integrated energy management system that affects the energy balance of the entire facility.

In this article, we explain how energy storage works in a single-family home and what processes occur in the system during daily operation.

Energy storage system architecture

A typical energy storage system consists of several basic components:

• PV generator - the energy source (photovoltaic modules),
• hybrid inverter - the central component that manages the energy flow,
• energy storage - usually lithium-ion (Li-ion / LiFePO₄),
• BMS (Battery Management System) - a system that supervises the operation of cells,
• EMS (Energy Management System) - system optimization layer,
• electrical and metering protections - to ensure safety and monitoring.

In solutions offered by distributors such as G-Volt, these systems are configured as complete solutions ready for integration into the end customer's installation.

Principle of operation of energy storage

1 Autoconsumption priority

The energy produced by the PV system first covers the current demand of the building. Direct consumption of energy reduces conversion and transmission losses.

2 Charging of the energy storage

When there is a surplus of energy production - usually between 10:00 am and 3:00 pm - the energy is directed to the storage. The charging process involves the conversion of electrical energy into chemical energy in the battery cells.

3 State of charge (SoC) management.

The BMS controls the level of charge (State of Charge) and battery operating parameters such as temperature, voltages and currents.

Based on this, the EMS makes decisions on whether to continue charging or put the system into standby mode.

4 Discharge of storage

When PV energy production drops - in the evening or at night - the energy storage discharges the stored energy to the home system.

The energy passes back through the inverter (DC → AC), powering the building's loads.

5 Interaction with the power grid

In an energy shortage situation, the system automatically draws energy from the power grid.

In the net-billing model, the export of energy to the grid takes place only after the storage is fully charged.

Modes of system operation

In practice, the energy storage can operate in several modes:

• self-consumption (self-consumption) - maximizing the use of own energy,
• backup (EPS / UPS) - emergency power supply during a power outage,
• time-of-use (TOU) - optimization of energy costs depending on tariffs,
• peakshaving - reduction of peak power drawn from the grid.

The choice of operating mode depends on the system configuration and the needs of the end user.

Efficiency and technical parameters

System efficiency

Total cycle efficiency (round-trip efficiency) is typically:

• 85-92% for Li-ion systems.

Losses are mainly due to:

• AC/DC and DC/AC conversion,
• thermal losses,
• operation of control electronics.

Lifetime

• 3000-8000 duty cycles,
• capacity degradation of about 1-3% per year.

Usable capacity

Nominal battery capacity is not fully available. Systems typically operate in the 10-90% SoC range to extend cell life.

What does this look like in practice?

For a typical single-family home:

• PV installation: 5-10 kWp,
• energy storage: 5-15 kWh.

Summer scenario

• Full charging of the storage during the day,
• coverage of evening and nighttime consumption,
• minimal energy consumption from the grid.

Winter scenario

• limited charging of storage,
• greater dependence on the grid,
• lower efficiency of the overall system.

Importance of energy storage for the market

From the RES market perspective, energy storage facilities:

• increase the value of PV installations,
• improve the rate of self-consumption,
• respond to changing energy billing models,
• support the stabilization of the electricity grid.

For installers, this means:

• proper selection of system capacity and power,
• knowledge of hybrid inverter configurations,
• integration of EMS and BMS systems.

Summary

Energy storage in a single-family home is an advanced power system designed to optimize the use of locally produced energy.

The system manages the flow of energy between the PV plant, the storage, the consumers and the power grid.

In practice, this means greater energy independence, better utilization of the PV plant and the ability to actively manage energy costs.

Bibliography

1. International Energy Agency, Energy Storage - Tracking Report, 2023.
2. IRENA, Electricity Storage and Renewables: Costs and Markets, 2017.
3. Fraunhofer ISE, Battery Storage Systems in Residential Applications, 2022.
4. National Renewable Energy Laboratory, Battery Storage Technology Overview, 2021.
5. Polish Power Grid, Power System Operation Reports, 2023.
6. Energy Regulatory Office, Electricity market in Poland - annual reports, 2023.
7. Hesse, H. et al, Lithium-Ion Battery Storage for the Grid, 2017.
8. Luo, X. et al., Overview of current development in electrical energy storage technologies, 2015.