Storage battery: what it is, how it works, and why it's really worth it in 2025

In an increasingly sustainability-oriented and energy-saving world, the photovoltaic storage battery represents one of the most relevant innovations in recent years. In simple terms, a storage battery is a device that allows you to store the energy produced by a photovoltaic system for use when the sun is not shining.
In this guide, we will analyze in a clear and in-depth manner the operation, advantages, costs, and opportunities offered by a battery for photovoltaics in the current context.

How a battery for photovoltaic systems works

Phases of the storage cycle: charge, storage, and discharge

The principle of operation is quite simple but ingenious. During the day, the photovoltaic panels produce energy. Part of it is used directly by the household appliances, while the excess is stored in the battery. When the system is not producing (at night or on cloudy days), the battery returns that energy, powering the home.

Interaction between battery, inverter, and power grid

The technological heart of the system is the inverter, which transforms the direct current produced by the panels into alternating current for household use. When the battery discharges or when demand is too high, the system draws from the public electricity grid, ensuring energy continuity.

Battery and hybrid inverter: how the integrated system works

A hybrid inverter integrates the functions of conversion and management of storage, simplifying the system and increasing overall efficiency. Some more advanced models also offer smart features to optimize self-consumption.

Smart management and automation of energy flows

Thanks to intelligent software and dedicated apps, the user can monitor and control in real-time production, storage, and consumption, setting priorities or custom scenarios based on their routine.

What types of photovoltaic batteries exist

Lithium batteries: the most used solution in 2025

Lithium batteries are currently the preferred choice for household systems. They offer high energy density, long lifespan (up to 15 years), and good charge/discharge efficiency. Lithium iron phosphate (LiFePO4) models are particularly safe and stable.

Alternative technologies: lead-acid, flow, and emerging solutions

Lead batteries, while cheaper, are less efficient and bulkier. Flow batteries and solid-state solutions are still in development but promise significant benefits in terms of scalability and sustainability.

Technical comparison between the various technologies

Duration

• Lithium: 10,000 cycles

• Lead: 1,500-2,000 cycles

Energy efficiency

• Lithium: 90-95%

• Lead: 75-85%

Safety

• LiFePO4: high thermal stability

• Lead: risk of acid leakage

Cost per usable kWh

• Lithium: medium-high

• Lead: low, but with short lifespan

How to properly size a battery for your home

Analysis of energy consumption and daily needs

To choose the right battery capacity, it is essential to know the average daily consumption of your home. A family of 4 typically consumes 10-12 kWh per day. If you want to maximize self-consumption, a battery of at least 5-10 kWh is recommended.

Relationship between photovoltaic system power and battery capacity

The battery capacity must be proportional to the system power. A 6 kWp system that produces 8,000 kWh/year requires at least a 10 kWh battery to make the most of the energy produced.

Practical examples: 3 kW, 6 kW, and above

• 3 kW: battery of 3-5 kWh

• 6 kW: battery of 7-10 kWh

• 6 kW: batteries of 10-15 kWh or modular

Advice for single-family and two-family homes

Single-family homes benefit more from self-consumption, while in two-family or small condominium settings, it is possible to opt for shared systems or expandable modular batteries.

How much does a photovoltaic battery cost and how long does it take to pay off

Factors influencing the price: capacity, brand, installation

The price ranges from 4,000 to 12,000 euros depending on capacity, technology, and brand. Installation and hybrid inverters account for 15-25% of the total cost.

Estimation of annual savings and calculation of return on investment

Thanks to a storage battery, self-consumption can increase by 50-70%, leading to savings on bills of up to 800-1,200 €/year. The average payback time is 6-9 years.

Incentives, deductions, and tax benefits available in 2025

Battery bonuses and self-consumption

Batteries may benefit from a 50% tax deduction for renovations, and in some cases, the Superbonus of 70-90% if integrated into larger projects.

Energy communities and shared storage

The option to share the produced and stored energy within a community is becoming increasingly popular, benefiting from advantageous rates and state contributions.

Installation and management of the photovoltaic battery

Who can install it and what is needed at the bureaucratic level

Installation must be carried out by certified FER technicians. It is necessary to update the GSE practice and, if the system exceeds certain limits, obtain municipal permissions.

Maintenance, lifespan, and warranty of the storage system

Modern batteries require little maintenance. Manufacturers offer warranties from 5 to 15 years, often covering at least 70-80% of the remaining capacity.

Monitoring via apps and smart portals

Apps and management software allow real-time monitoring of the battery's status, charge cycles, and consumption. Some solutions also provide suggestions to optimize energy use.

What happens in case of a blackout?

If paired with a backup-function inverter, the battery can power the home even during a power outage, ensuring continuity to lights, refrigerator, and essential devices.

Storage and electric mobility: a winning combination

How to use the battery also for electric car charging

The storage battery can be used to power a home wallbox, allowing you to charge your car with solar energy even at night.

Bidirectional technologies: V2H and V2G in residential settings

With Vehicle-to-Home (V2H), the car becomes a mobile battery. With Vehicle-to-Grid (V2G), the energy from the car can be returned to the grid. These technologies are on the rise and promise an even more flexible future.

Integration with smart wallboxes

The new smart wallboxes allow for dynamic charging management, taking into account photovoltaic production and battery availability, avoiding waste and overloads.

The future of photovoltaic batteries in Italy and Europe

Upcoming innovations: solid-state batteries, AI, and microgrids

Research is focusing on safer, more durable, and high-performance batteries. Solid-state batteries promise 50% more energy density and longer life cycles. Artificial intelligence will allow for predictive management of consumption, while local microgrids will transform how we share and manage energy.

The role of storage in the energy transition and grid parity

Batteries are key to making photovoltaics stable and continuous. They reduce demand peaks and contribute to grid stability, accelerating the transition towards a decentralized and sustainable model.

Towards an increasingly independent home: the off-grid model

In some rural or hard-to-reach areas, the off-grid model is already a reality. With large capacity batteries, well-sized systems, and intelligent management, it is possible to live completely disconnected from the electricity grid.

FAQs about photovoltaic batteries

Is a battery mandatory in a photovoltaic system?

No, but it is highly recommended to increase self-consumption and make the system more efficient.

What is the average lifespan of a lithium battery?

Between 10 and 15 years, depending on the number of cycles and the quality of the product.

Can I install it after the photovoltaic system?

Yes, but it is better to plan for it from the outset to optimize costs and technical compatibility.

Is it more convenient to have a battery or a net metering contract?

It depends on consumption: for those who consume a lot in the evening, the battery offers greater savings. The net metering system is still being replaced by the widespread self-consumption mechanism.

Does the battery work at night?

Yes, it is during the night hours that it comes into play to power the home with the energy accumulated during the day.

If you desire a more independent, efficient, and sustainable future, a storage battery is one of the smartest choices you can make today. And if you have doubts, talk to a certified installer: they will be able to recommend the best system for your home.