6 things to know before installing a photovoltaic system

Solar energy is one of the most effective solutions to reduce dependence on the electrical grid and lower electricity bills. A properly sized photovoltaic system can cover most of a home's energy needs, ensuring significant long-term savings. In this guide, we analyze the operation of a photovoltaic system, costs, achievable savings, tax incentives, and necessary permits. 

1. How does a photovoltaic system work? 

A photovoltaic system converts sunlight into electricity through solar panels placed on the roof or in a sun-exposed area. The energy produced is initially direct current and is converted into alternating current by the inverter, making it usable for household consumption.

If the system is equipped with storage batteries, excess energy is stored and used when the sun is not available, increasing self-consumption and further reducing dependence on the electrical grid. 

2. What are the costs of a photovoltaic system?

The price of a photovoltaic system depends on several factors:

• System power (e.g., 3 kW, 6 kW, 10 kW)

• Type of panels (monocrystalline, polycrystalline)

• Presence of storage batteries

• Cost of the inverter and installation labor

Here is an estimate of average costs:

• A 3 kW system without storage costs between 4,500 and 7,000 euros.

• A 3 kW system with storage can exceed 10,000 euros.

3. How much can you save with photovoltaics?

Savings depend on the amount of self-produced and self-consumed energy. A properly sized system can reduce the electricity bill by up to 70%.

Here are some examples of average annual savings:

• 3 kW system without storage: approximately €450 annual savings

• 3 kW system with storage: savings increase thanks to stored energy, further reducing grid withdrawal. 

4. Incentives and tax deductions for photovoltaics in 2025

In 2025, several incentives are available for those who decide to install a photovoltaic system:

50% tax deduction

Installation of photovoltaic systems benefits from the Home Bonus, which allows a 50% tax deduction on a maximum expense of 96,000 euros. This incentive is intended for systems used for residential purposes, regardless of the primary or secondary status of the property, and covers systems with a maximum power of 20 kW. The deduction is divided into 10 equal annual installments, making the investment more accessible. 

Reduced VAT at 10% 

For the purchase and installation of a photovoltaic system, a reduced VAT rate of 10% applies, covering both materials and installation services. This measure helps further reduce costs and promotes the spread of solar energy.

Changes in the net metering mechanism

From 2025, the net metering system for new photovoltaic installations will be gradually phased out. However, new incentive tools are planned for energy produced but not self-consumed, to ensure an economic return for system owners. 

5. Authorizations and permits: what is needed?

Generally, installing a photovoltaic system on residential buildings does not require special permits, especially if the intervention does not alter the building's silhouette and complies with municipal regulations. However, exceptions exist:

• Historical or protected buildings: if the property is subject to landscape or historical constraints, specific authorizations from the competent authorities are required.

• Local regulations: it is essential to check with your municipality, as specific rules regarding photovoltaic panel installation may apply.

It is always advisable to consult a professional or the municipal technical office to ensure compliance with all regulations before proceeding with the installation.

6. Maintenance and lifespan of the system

Maintenance of a photovoltaic system is generally minimal, making it a practical and reliable energy solution. Main maintenance activities include:

• Cleaning the solar panels: dust and debris can reduce panel efficiency. Although rain can help with natural cleaning, manual cleaning every 6 to 12 months is recommended to ensure optimal performance.

• Monitoring the photovoltaic inverter: the inverter is a crucial component that converts direct current generated by the panels into usable alternating current. Periodic performance checks ensure efficient system operation.

Regarding lifespan, photovoltaic modules have an estimated operational life of about 30 years. However, it is important to note that module power decreases over time due to exposure to solar radiation and other external conditions. This phenomenon, known as photovoltaic module degradation, results in an annual power loss between 0.8% and 1.0% for crystalline silicon modules.

Installing a photovoltaic system is a profitable investment, but staying informed is essential. Learn more about choosing the ideal panel size in our guide: Photovoltaic Panel Sizes. For further insights, visit our blog!