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How solar panels work
In 2024, 21% of electricity in Spain was generated by solar photovoltaic energy—a significant increase from 2023, when it accounted for 17%. The forecast for 2025: installed solar capacity is expected to surpass the 32,042 MW reached in 2024, overtaking wind power for the first time, which stood at 32,006 MW. According to data from Red Eléctrica Española obtained this month, installed solar capacity in Spain has reached 33,582 MW.
But let's start from the beginning—do you know what a photovoltaic panel is and how it works? We'll tell you.
Solar panels are becoming increasingly common due to their huge potential for clean energy production. Spain gets some 25,000 hours of sunshine a year on average, so not only can we use these devices to generate energy in a sustainable way thanks to the sun, but it is also a great opportunity to save and generate renewable energy at the same time.
But how does a solar panel work? How are they used to generate energy?
It's like this:
There are two types of panels: solar thermal collectors and solar photovoltaic panels. Let's look at what each of them does.
Solar thermal collectors
These are devices that make use of solar energy in a simple manner. Basically, they work through an accumulator which transfers heat to the water we want to heat. In some of these devices, the water is stored elsewhere, circulates and is heated as it passes through the collector. Solar thermal systems, on the other hand, heat the water in their own storage unit.
Photovoltaic solar panels
They consist of photovoltaic cells, which harness the sun's energy. The sunlight generates electricity, through the photovoltaic effect. How?
Photons are particles of electromagnetic radiation which include, for example, gamma rays, X-rays, ultraviolet light, visible light or infrared light. The action of photons releases electrons, which as they move about generate positive and negative charges on nearby semiconductors, creating an electric field capable of creating an electric current.
Alexander Edmond Becquerel was the first person to study how the sun affected electromagnetism. Based on his research, the inventor Charles Fritts, used selenium, brass and gold as a conductor to create the first photovoltaic cell in 1833. It took 120 years to be perfected. Bell Laboratories introduced the first modern photovoltaic cell in 1954.
Early applications of photovoltaic cells were heavily constrained by the cost of production. However, they began to be used in the "space race": The US satellite Vanguard 1, launched in 1958, used them and was able to remain operational for over 7 years.
In the late 1960s and 1970s, due to the oil crisis, new investments improved these photovoltaic cells and made them cheaper to produce, with the aim of positioning them as an alternative energy source. Industrial production began and they were installed all over the world.
It was in Japan that a photovoltaic solar panel was first used commercially: in 1966, a 225 W panel was installed to supply the Ogami lighthouse with electrical power. This solar panel raised people's awareness about the commercial use of this sustainable energy.
In the mid-1970s, photovoltaic panels were used to supply energy to oil platforms, berths or buoys, and in the 1990s, they began to be a common sight all over the world.
What goes into a photovoltaic panel?
Solar panels are made up of several photovoltaic cells with a surface area of about 10 square centimetres with a protective coating made of materials such as ethylene and vinyl acetate. These devices need to allow sunlight to pass through, but they are exposed to extreme conditions and very high temperatures.
The panels usually have a DC to AC inverter- alternating current being the current commonly used.
The panels are usually angled to take advantage of the sun's trajectory. However, some installations are fitted with a tracking mechanism that actually moves the panels to follow the sun's trajectory.
A solar panel's maximum output is between 300 and 450 W on average, per hour of sunshine.
Solar batteries: the main allies of photovoltaic panels
The electricity generated by the panels is used for self-consumption or fed into the grid. However, the panels cannot generate electricity at night or on cloudy days. This is where solar batteries come into play. They are an essential component of modern energy systems, as they store electricity and ensure a continuous power supply.
Batteries for solar panels have become a common added feature in off-grid energy installations as well as in hybrid systems, which aim to increase energy independence and reduce costs. They are also extremely useful in single-family homes or buildings located in remote areas where the electricity supply is not consistent.
At Endesa, we want you to make the most of this combination of solar panels and batteries. This spring, let savings blossom on your energy bill with a very special promotion: sign up for the installation of your solar panels with the Solar Cero Tariff and enjoy up to 2 years of free electricity. In addition, you’ll receive the battery at no additional cost, plus a free virtual VISA card* preloaded with €500.
Finally, you'll benefit from a 12-year warranty and financing of up to 120 months for your self-consumption installation, which includes our new monocrystalline 435 Wp PV panels. These panels offer an impressive 22% efficiency—among the highest on the market—feature a stylish Black Frame design, and come with a 30-year performance guarantee of 87% output.
This promotion is valid from 2 April to 31 May. Check the terms and conditions below and in our promotions and winners section.
Make the most of the sun’s energy and combine your photovoltaic solar panels with our Solar Cero Tariff this spring, just as the season is getting started.
Photovoltaic energy in Spain
Spain generates an average of 3,111 GWh of photovoltaic energy per month, according to Red Eléctrica Española (REE). However, electricity generation tends to vary throughout the year, with higher generation occurring during the summer months thanks to the increased hours of sunlight. A monthly record was reached with 5,817 GWh of energy generated in July 2024.
This month, according to data from the Spanish Solar Photovoltaic Association (UNEF), Spain ranks second in Europe in terms of total accumulated photovoltaic capacity, behind just Germany, which continues to lead with approximately 99.3 gigawatts (GW).
Spain’s largest photovoltaic installation by capacity is the Francisco Pizarro power plant, located in the province of Cáceres. Inaugurated in 2022, it spans 1,300 hectares and houses 1,494,240 solar modules. It is currently considered the largest photovoltaic installation in Europe, with a total installed capacity of 553 MW and a peak power output of 500 MW, enough to supply electricity to over 300,000 households. To put it into perspective, the largest solar power plant in the world—Bhadla Solar Park in India—has a capacity of 2,245 MW, double the output of a nuclear power plant.
The forecast for this year is that Spain’s photovoltaic electricity generation will continue its strong upward trend. The country is expected to surpass the 32,042 MW of installed capacity reached in 2024 (which already stood at 33,582 MW this month). This growth could be driven by factors such as decreasing solar panel costs and increased investment in renewable energies.
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You don't need to adapt to Endesa's tariffs because they adapt to you. If you go to our catalogue you can compare the different tariffs for yourself. Or if you prefer, you can answer a few questions and we will take care of comparing all the different electricity and gas tariffs and then make a customised recommendation.
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