Guía solar sobre energía solar

Solar Guide

Solar energy for your home ABC - Z! Basics and more

Last updated: January 4, 2023

Understanding the solar energy’s world

Welcome! 👋

At Quiero Sol we are happy to welcome you to this exciting world of solar energy. ☀️ We will be with you throughout your journey and we will accompany you on your solar experience. Our mission is that you understand the basic concepts (and not so basic if you want to go further and deepen), before buying, understand them when you have a conversation with an installer and make a decision with enough knowledge and the confidence you need. to take the step towards solar energy.

When you finish this section, you will see that it has been a good investment of your time, because solar energy will play an important role in the world's energy future.

Let's get started!

Table of contents

1: ABC of solar energy 🔤

To be aware of the fundamental and necessary solar knowledge when speaking with a solar installer 😉

  • 1: Solar energy and solar power are not the same

Photovoltaic effect - How solar energy works - Direct current - Electric current - Alternating current - Renewable energy sources - Types of solar energy that exist

  • 2: Difference between power (kW), energy (kWh), and its breakdown: kilo (k), Watt (W), hour (h)

Electrical power - Volt - Voltage - Megawatt hour - Megawatt - Kilowatt hour - Kilowatt - Gigawatt - How your home uses solar energy

  • 3: Types of installations: connected to the electrical network, isolated, surplus, batteries (in general). Components of an installation.

The four main components of a solar energy system - ICP - Difference between retailer and distributor - Electric retailer - Electric distributor - REE - How energy is generated in Spain - Energy mix Spain - The price of 1 kWh of the conventional network vs. price of 1 kWh of your surplus photovoltaic energy

  • 4: Types of roofs: size, orientation, inclination, shadows

The basic concepts of orientation/tilt for optimal solar electricity generation - Solar irradiation. Solar capital in Spain. Take advantage of the solar potential to save on your bill

  • 5: High and low installation costs: why there are extremes and what I need to know

What range of costs can you expect to pay for quality solar power

  • 6: Guarantees for the consumer

What guarantees do solar panels and other components have?

  • 7: Incentives for solar self-consumption and current electricity prices.

Validity of the "solar tax" - Aid and subsidies available for solar self-consumption in 2022 - Income tax deduction for the installation of solar panels - Reduced VAT on the installation of solar panels for self-consumption: when yes and when not?

2: The energy consumption of your home 🏡

Because not all homes or families are the same: to be aware of the particular situation in your home, understand your consumption habits and which system best suits you 😎

  •  1: Understand how suitable the home is for self-consumption installation, analysing the best and worst generation scenarios, to make the decision to install. Our Solar Calculator
  • 2: Differentiate household consumption throughout the day, understand consumer behaviour - Single-phase, two-phase and three-phase households: what they mean.
  • 3: Dimension of the installation, number of panels, amount of energy required, amount of installed power. How will the water be heated: with solar energy? This decision can affect the number of panels you will need - Heating with solar panels in your home?

How is the process of a solar installation? How does an installation of solar panels for self-consumption work?

Complete guide on permits required for the installation of solar panels- How to calculate the number of solar panels I need. How many solar panels should you buy?

  • 4: Products. A. Difference of monocrystalline, polycrystalline panels. Brands: cheap, expensive. How to know which one to choose?

B. Which inverter to buy. What is an inverter? Are microinverters suitable? Pros and cons

Different means to access self-consumption in your home: purchase, rental, financing. How to pay the system?

  • 5: Monitor the installation. Post installation: tips to get the most out of your photovoltaic installation - How to maximise the performance of solar panels. Cleaning. Maintenance - The efficiency of the plates and the energy production, is it the same all year round?

What happens in winter with the photovoltaic installation? - Climates and seasons of the year: how do they affect the production of photovoltaic energy?

  • 6: Savings, return on investment, sale of surpluses, calculate amortisation

Compensation of surpluses - How to amortise the investment in solar panels. Cost effectiveness. IBI, ICIO discounts. Solar reimbursement. How to Calculate Savings and Payback for a Solar System.

3: Storage for solar installations. 

All you need to know 😊🔋

  • Is it worth it now or later?
  • Do I need them? Are they expensive?
  • Will I generate more savings?
  • Technological advances

4: Electric vehicles 🚗🔌

  • Sizing the solar system  for VE
  • Type of chargers
  • Batteries yes or no to charge the VE?

1: ABC of solar energy 🔤

To be aware of the fundamental and necessary solar knowledge when speaking with a solar installer 😉

The energy provided by the Sun is out there every day. Whether we see it or not, the Sun rises every morning and sets every evening, and it doesn't fail! Solar energy is clean and inexhaustible energy -which makes it excellent for the environment since it does not damage it as fossil fuels do- and we can take advantage of it.

What good is it to us? To save money on electricity bills month after month and year after year for at least 25 years, no matter what happens with the economy and electricity prices. 💪 Also, in Spain, after two years on the roof, a solar panel will have generated more energy than was needed for its production.

So that you can get the most out of this renewable source of energy, we will help you understand how it works, so that you can make the best decisions and amortise the investment you have made in solar energy in a shorter period of time. That's why Quiero Sol exists!

So let's continue to see how solar energy works, but not before making a small parenthesis to explain what we mean when we talk about renewable energy sources.

Renewable energies are those obtained from natural resources that produce energy in an inexhaustible way and are clean energy sources. Unlike fossil fuels, they do not produce greenhouse gases that cause climate change, nor polluting emissions into the atmosphere. Examples of renewable energies are:

  • Solar energy: the energy obtained from the Sun. The main technologies are solar photovoltaic (uses sunlight) and solar thermal (uses heat from the Sun).
  • Wind energy: obtained from the wind.
  • Hydraulic or hydroelectric energy: obtained from rivers and freshwater streams.
  • Biomass and biogas: which is extracted from organic matter.
  • Geothermal energy: the heat energy contained in the interior of the Earth.
  • Tidal energy: obtained from the tides.
  • Wave energy: obtained from waves.
  • Bioethanol: organic fuel suitable for the automotive industry that is achieved through fermentation processes of vegetable products.
  • Biodiesel: organic fuel for the automotive industry, for example, which is obtained from vegetable oils.

Great! Now yes, let's continue!

Without solar energy, your home consumes electricity from the network to meet consumption needs (washing machine, toaster, oven, light, etc.). Solar panels will work on your roof (as long as it's not heavily shaded) by capturing the sun's energy in the form of light, and converting it to electricity for your home to use.

If you produce more electricity than your house needs, that excess energy will simply go to the electricity grid and you will be able to receive financial compensation for it (this is the so-called compensation for surpluses, but don't worry, we will see it in detail more ahead).

But if for example you had a storage battery, you could save your surplus energy produced in it to use it when the Sun is no longer there and your panels do not produce energy. On the contrary, if you are not producing enough energy with your solar panels, then your home takes part of what it needs from the grid.

We want you to feel well informed and informed by the time you start a conversation with an installer, and that you can obtain all the benefits of this clean energy such as solar.

Keep reading this guide that we have made for you!

1. Difference between solar energy and solar power

Did you know that they are two different concepts? When the electrical current flows through the wires slowly, then the electrical current has low power. But if the electric current flows through the wires quickly, then the electric current has high power. Power is measured in kilowatts (kW).

Solar systems are sized in kilowatts, that is, by how much electrical power it produces.

Let's take for a moment an example of real power in a home with 12 solar panels installed on its roof. Each panel is 400 watts, so:

12 panels x 400 W (watts) = 4,800 W = 4.8 kW considering that 1 kW is equal to 1,000 W

Therefore, we can say that this installation is a 4.8 kWp solar system (peak kilowatts of production in its best conditions). Avoid the temptation (and confusion really) to think that this system will produce 4.8 kW all day, ⚠️ since it will produce this at noon on a perfect sunny day (clear and sunny skies but not too hot).


Example of average daily solar irradiation on an October day in Barcelona, Spain. System angle: 37° reaching its peak at noon. Source: PVGIS Photovoltaic Geographical Information System software.

Energy, on the other hand, is measured in kilowatt-hours (kWh) and refers to the amount of energy used, generated or stored over time. If the electrical current is of low power, the energy will be less during that period of time compared to a high power electrical current.


  • Power is measured in kilowatts (kW)
  • Kilowatt-hour (kWh) = measure of energy, not power. Where:
  • kilo means thousand
  • W stands for watt, it is a measure of power
  • Hour, a measure of time

2. Energy produced by your solar system

Continuing with the previous example, for a 4.8 kW solar system that receives an annual average of 5 hours of sunshine per day in Spain (an average that compensates for the higher radiation in summer and less in winter), the result is 24 kWh on an average day. Where:

4.8 kW x 5 hours = 24 kWh

This number referring to the number of hours of Sun will depend on the irradiation of your particular city. For example, it will be higher in a city in the south of Andalucía, and lower in a city in the north of Galicia.


Example of system energy production in Madrid, Spain. Inclination of 36°, with generation peaks in summer. Source: PVGIS Photovoltaic Geographical Information System software.

🤓 Important:

In practice, 20% less than the maximum rated power is often obtained due to unavoidable losses in the system, such as: dirt on the panels, the resistance of the cables to the roof, solar inverter losses and/or temperature losses of solar panels.

3. Anatomy and functioning of a solar system

a. What does a solar system look like on your roof?


Components of a solar system.

  • Photovoltaic cells or photovoltaic modules (solar panels): absorb sunlight and produce direct electric current.
  • Solar inverter: device that takes direct current from the solar modules and converts it into alternating current, which is what your home needs and uses.
  • Electrical panel: where your home connects to the grid, and for your solar system the inverter will also connect.
  • Consumption monitor: it is highly recommended to have it to know in detail your consumption hour by hour and also your solar production every hour. It will allow you to adapt your consumption according to your production and thus maximise solar generation.
  • Counter: it will allow you to know how much electricity you are importing from the grid and how much of your solar energy you are exporting to it.
  • Storage battery (if you have one): take advantage of and save the excess energy generated by your system for when what the panels provide is not enough, you experience a power outage or the Sun is gone.

Finally, we believe that it is worth explaining what the ICP is. The Power Control Switch (Interruptor de Control de Potencia in Spanish) is a device installed at home, which is used to cut off the supply when the electrical power has been exceeded. This occurs, for example, when connecting a large number of electrical appliances at the same time. The ICP is located in the main control panel, which means that it is inside the house and the only thing you have to do if it is disconnected is to reconnect it again.

There are different types of solar energy systems:

  • Solar on grid: the most common. If you want to save money and already have a connection to the grid, then grid-connected solar power is a great option.
  • Off grid solar: should have batteries and backup generator.
  • Hybrid solar: one that has batteries and a battery inverter and is also connected to the grid.

b. Solar System Operation

Sunlight hits the photovoltaic cell or module and causes the electron associated with the atom in the panel to free itself from its position. When another electron finds that space freed up, that's when energy is produced. Electrons move and in this way energy is produced. This process is known as the photovoltaic effect.

Learn more with us about solar panels here!

4. Solar system location

In Spain, the Sun rises in the east, moves in the south and sets in the west. If your case is one whose routine is very marked and has higher energy consumption needs during the morning, then having your solar system facing east is the ideal option, since the Sun rises precisely on that side! 🌞 And you'll be taking advantage of direct sunlight from the first moment (which is always stronger than indirect).

Also, if no one is home during the day, another solution would be to have half the panels facing east and the other half facing west. Surely, your percentage of production during an average day will be less than a south-facing system, but in your particular case it will produce more when you really need it, both in the morning and in the afternoon when you return home and need to satisfy your needs. consumption.

If, for example, your solar system is facing south, during the morning it will be receiving sunlight, only indirectly. But come midday when the Sun is at its strongest, your home will produce more and capture all of the direct sunlight by facing south.


The best direction to place your solar system is on a south-facing roof if you want to get as much energy as possible for a year. However, it is also a good alternative to place it on roofs facing east or west, where it will give you more energy in the morning and late afternoon respectively, but knowing that they will produce less energy in general. Still, it will make your electricity production better synchronized with your usage habits.

Find out more about installing solar panels in your city!

5. Solar system costs

You're probably wondering what range of costs you can expect to pay for a quality solar energy system, aren't you? Or maybe, why is there a wide range of possibilities and so extreme (both for high and low costs)?

In Spain, the cost of a photovoltaic solar energy system for a single-family home is today around €1 per kWh of annual consumption on average (between 0.8 and 1.4). For example, for a home with a consumption of 5,000 kWh per year, the cost of the system will be between approximately €4,000 and €7,000.

For these systems a VAT of 21% is applied. A residential owner or an individual cannot offset the VAT on the invoice as they are the final consumer. However, there are cases of reduced VAT for the installation of solar panels for self-consumption. But when does it apply and when does it not?

There are some very specific circumstances in which a reduced VAT of 10% could be applied instead of 21%, which represents a decrease of 11%. But you have to be careful with this, because it has very specific requirements. Therefore, a reduced VAT cannot be applied to photovoltaic solar energy, unless the system itself is part of a rehabilitation and adaptation project and the cost of the system materials does not exceed 40% of the investment.

6: Solar system warranties

Los sistemas de energía solar cuentan con cuatro o cinco garantías principales:

  • Solar energy systems have four or five main guarantees:
  • Panel performance warranty: 25 years (industry standard)
  • Solar panel product warranty: normally 10-12 years
  • Inverter warranty: generally 5 years (varies by manufacturer, and can be up to 10 years)
  • Battery warranty (in case of adding batteries): 10 years
  • Installation warranty: 2 years and some installers offer up to 3.

7: Incentives for solar systems and current electricity prices

a. Incentives

First of all, it is worth clarifying that many people still believe today that the "solar tax" is still in force. Well, here's the good news if you didn't already know: no! 🎉Since 2018, Spanish regulations guarantee the right to self-consume renewable energy without charge.

By the way, the recent and important change, Royal Decree 244/19, allows you to receive compensation for your surplus energy, install in communities and buildings, not pay fees for your solar energy and has also simplified the bureaucracy of paperwork and permits.

  • Most Town Halls offer discounts on your IBI (Real Estate Tax) in which you can save up to 50% for 5 years, and 95% on the ICIO (Construction and Installation Tax). It depends on each municipality in particular. You can see more about the specific case of your city > Solar Panel Installation 👀
  • The NextGeneration EU funds or European funds are an incentive for self-consumption, in the form of subsidies and aid for solar systems. A recovery plan that constitutes a unique opportunity to promote self-consumption of energy and that will also reduce polluting CO2 (carbon dioxide) emissions.

A subsidy is then an economic incentive perceived by people and granted from a public body. To help carry out an activity that requires a high investment or that citizens could not afford on their own.

The Recovery, Transformation and Resilience Plan is aimed at repairing the damage caused by the pandemic crisis, and through reforms and investments, building a more sustainable future. The Government of Spain has approved in 2021, 660 million to encourage photovoltaic energy and sustainable consumption, expandable up to 1,320 million euros as long as the Autonomous Communities continue to require the money.

  • The personal income tax deduction for solar systems came into force on October 6, 2021 as one of the urgent measures approved by the Government to promote building rehabilitation activity (Royal Decree-Law 19/2021).

This change in the regulations is part of the Recovery, Transformation and Resilience Plan of the MITECO (Ministry for the Ecological Transition and the Demographic Challenge), according to which people who carry out a rehabilitation in their home can deduct up to 60% on the Personal Income Tax (IRPF). In order to access this, you must meet the requirements established by the Tax Agency, such as that the applicant must be the owner of the home and the installation must be carried out by authorised companies. The deduction can range from 20%, 40% and up to 60% of the investment.

🤓 Important!

You can see more about the specific case of your city regarding IBI, ICIO, personal income tax and grants from European funds here. 👀

b. Current electricity prices

The Red Eléctrica de España (REE) has indicated that the electricity prices of the network (from October 2021 to September 2022 included, that is, 12 months), with their ups and downs, have averaged around €0.225/kWh (225 €/MWh). A home without a solar energy system that consumes the average 270 kWh per month from the network that Spanish households consume according to the REE, would pay around €60 per month on its bill, and around €730 for the 3,240 kWh per year in the variable part of electricity consumption. The fixed charge of the electricity bill is independent of consumption and is an amount that is billed for the simple fact of being connected to the network and for the contracted power.

We take advantage of this space to see the basic difference between distributor and marketer since we know that it is not always completely clear. Let’s go for it!

Mainly it is the role that each of them plays. You contract the electricity with a marketer and it is responsible for selling you the electricity and carrying out all the necessary procedures with the electricity distributor. The distributor owns the cable and the energy, and for example, you will never run out of electricity even if you change the marketer over and over again. Your CUPS as a client (Universal Supply Point Code, Código Universal de Punto de Suministro in Spanish) is the physical supply point where the connection connects with the distributor's electrical network. In other words, it is the point where the electrical system is hooked up to obtain energy.

Data that you will be interested to know about this renewable energy:

  • The Guarantee of Origin System (GdO in Spanish) began to be applied in Spain in 2007 and is responsible for the National Commission of Markets and Competition (CNMC). The Guarantee of Origin certifies that a specific amount of kilowatt-hours (kWh) of electricity has been generated through renewable energies and in electricity bills, the marketer is obliged to provide its clients with the corresponding Certificate to the GdO issued by the CNMC.
  • Generation from renewable energy sources in Spain in 2021 represented 46.2% of the national mix, compared to 44% in 2020 and 37.5% in 2019. 📈
  • Photovoltaic solar energy, particularly, in Spain in 2021 has generated 1,018 GWh, which is 37% more than in December 2020. 📈 Its contribution to the national mix has been 4.3%.

2: The electricity consumption of your home 🏡

Because not all homes or families are the same. To have knowledge of the particular situation in your home, understand your consumption habits and which system is best suited to you 😎

Now that you have a foundation of essential knowledge needed to understand solar energy, in this section we will look at how it relates to your home and your bill, and go into detail about what type of solar panels to buy and how many you should put on your roof.

To address these issues, we invite you to first think about the following: what are you trying to solve with your future solar system in your home? Is your main motivation to ensure low electricity bills for decades to come? Would you be satisfied with savings -in the worst case- of 10%? Do you want to aim to have savings for self-consumption in the best case of 70%?

To get these answers, the ideal is to measure the amount of energy you use during the day, when the Sun shines, and the amount you use at night. With these numbers, you can make a good estimate of the economic performance of the solar energy system in your home, before obtaining the different quotes.

1. Solar Calculator

You don't have a solar installation on your roof yet and you want to know what your electricity bills will be like in the future with a solar system? We can help you! Our Solar Calculator will answer your question.

We help you understand how suitable your home is to have a solar energy system, analysing different generation scenarios, so that you can make the decision to install.

You can easily find out how much energy you use in 24 hours, on average, as this is listed on your electricity bill. Let's look at the following breakdown and example of an electricity bill without a solar system:

Concept                         Base                        Unit price                     Amount

Power                           5.50 kW                 €0.104/kW day            €17.15

Energy                          155 kWh                €0.150/kWh                 €23.10

Social bonus                                                                                      €0.35

Electricity tax               €40.60                      5.113%                       €2.08

Meter rental                                                                                        €0.80

VAT                                €43.48                      21.00%                       €9.13

Total                                                                                                           €52.61 

This example is the case of a home that uses 5.2 kWh of electricity per day, on average (155 kWh / 30 days). We recommend that you look at a recent bill and find your average daily usage, which varies based on your lifestyle and the efficiency of your home. The REE (Red Eléctrica España) indicates that Spanish households consume an average of 9 kWh per day and approximately 270 kWh per month, which represents about 3,240 kWh/year.

Just keep in mind that these numbers can vary with the seasons. If you have electric heating or cooling and use it a lot more in summer and winter, your daily usage during these seasons will probably be higher. But we don't want to complicate you. The average values are already good enough to take as a reference. 😉

2. Electric connection, rates and bill

Next, we will explain the different types of electrical connection (single-phase, two-phase or three-phase), the types of rates that you can have contracted in Spain (regulated or free market rate) and we will help you interpret the elements on your bill.

a. Phases

  • Single Phase: This means they have a live wire to your house that carries the electricity. This wire is called the hot conductor and there is a second wire, called the neutral conductor, which provides a return path.
  • Two phase: means that there are two live wires going to your house.
  • Three phases: As people get larger homes and more powerful appliances like large air conditioners and pool heaters, they may need more power than can flow through a single wire. For this reason, more and more homes have three-phase connections. Yes you are correct! Three-phase means that it has three live or active wires instead of one or two. If you have three-phase power, single-phase appliances run on one of those phases, and any large three-phase appliance is connected to all three phases. As electric vehicles become commonplace, people will start to upgrade to three phases to be able to charge it faster.

b. Type of electricity supply contracted and differentiation of rates

  • Regulated electricity market

The regulated electricity market is the one that offers the Small Consumer Voluntary Price (PVPC rate, Precio Voluntario al Pequeño Consumidor in Spanish). Its prices are regulated by the electricity market and supervised by the Ministry of Industry, Energy and Tourism. Its price varies every hour of every day based on the supply and demand of energy. The users who contract the PVPC have hourly discrimination in three mandatory periods: peak, flat and valley. It is important to note that only the so-called reference marketers can operate in this regulated electricity market.

  • The peak period: higher tolls and regulated charges.
  • The flat period: with an intermediate impact of these regulated costs.
  • The valley period: period in which these tolls and charges are lower.

Electricity costs are discriminated by schedules. National Commission of Markets and Competition (CNMC).

  • Free market

In this market there is a great variety of companies that offer electricity, gas and maintenance services with the prices that they set themselves. These companies offer more varied electricity rates: stable price, hourly discrimination and flat rates.

  • Components of the electricity bill
  • The cost of energy
  • The margin for the marketer for the services provided
  • Meter equipment rental
  • Taxes

Without a solar energy system in your home, we recommend you pay attention and recognize your different consumption throughout the day to understand your behaviour as a consumer and thus adjust your needs based on the different hourly discriminations and rates that exist to save on your invoice.

3. Solar system dimensions

Surely you remember that solar systems are sized according to the power (kW) they can generate at noon on a perfect sunny day.

Clarification! If you don't remember very well the concept of kW of power or kWh of energy, don't worry, you can always come back to our section "1: Difference between solar energy and solar power"!

For example:

3 panels of 250W = 750W of power → But what does this figure really mean?

750W x 5 hours of Sun per day (average) = 3,750Wh which is equal to 3.75 kWh of solar energy in one day

To know the size of the solar system you need, you will have to consider your electricity consumption (which we have seen in the previous section), the money you want to invest, the size of the roof or surface to be installed in your house, the location geographic location, and whether you want solar energy to cover all your electrical energy needs or just a few.

To mention an example, it is not the same if you want your solar system to be in charge of heating the water or not; if you have an existing gas hot water system that you want to keep; or do you prefer an electric hot water system; or solar thermal or an aerothermal system.

As a guide, we can say that for annual consumption of 2,000 to 4,000 kWh, 4 to 6 solar panels are needed; for consumption between 4,000 and 6,000 kWh, from 7 to 9 plates; for annual consumption of 6,000 to 8,000 kWh, from 7 to 9 panels; for consumption between 6,000 and 8,000 kWh per year, from 10 to 15 solar panels, and for consumption between 8,000 and 10,000 kWh, from 16 to 20 photovoltaic panels.

4. Products and payment methods

a. Monocrystalline and polycrystalline panels

The difference between these two, when they are of similar rated output power (maximum power under normal use conditions), is minimal in terms of their performance in practice. The important thing is to choose a good brand that will last at least 25 years in your system.

They are normally differentiated by factors such as the geographical area and the climate in which your home is located. It is recommended to install monocrystalline solar panels in cold climates since they better absorb solar radiation when there is snow, fog or storms, and install polycrystalline panels in warm climates. Still, monocrystalline solar panels are better value for money.

b. Solar inverters

After the panels, the solar inverter is the most important part of the solar system. Its job is to convert the direct current produced by the solar panels to the alternating current that your home needs to use. There are inverters (a kind of large box that is located on the wall and connected to the panels), and microinverters (smaller and located behind the panels).

The difference between these is that when you use microinverters, each of the panels works independently, so if one is receiving shade, only that panel will drop in performance while the others continue to work without a problem. In addition, it allows you to monitor the performance of each solar panel individually. However, the downside of microinverters is that they are expensive and can add about 25% more to your system budget. There are also some optimizers that perform the same function as microinverters and can be cheaper.

To choose an inverter, it is best to choose a recognized and reputable brand that offers a 10-year guarantee. It is advisable to have a 3-phase inverter for a 3-phase home, so that the current flows through all 3 cables and not just one, and thus avoid overvoltage problems.

c. Ways to pay the system

Different ways to access the solar system in your house:

  • Purchase in cash: you own your panels and all the energy produced in them without the need for monthly payments. The purchase offers the highest profitability, since the system is yours from day 1. However, we know that it requires an initial investment on your part.
  • Use of financing: accessing loans from a bank or financial entity.
  • Rent: you pay a monthly fee for your system, it offers savings from the first day and avoids any initial investment.

5. The importance of monitoring your solar system

Through the monitoring application, you can see in real time how your solar system is working. For example, if your panels are producing 4 kW and your home is only consuming 3 kW, it means that the remaining kW is being fed into the grid. But what if you decided to turn on some electrical appliances? The scenario now changes and instead of giving your surplus to the network, you will be taking from it to complete your consumption needs. Your home will be consuming, for example, 4.5 kW of energy, and you will be taking from the network that 0.5 kW of difference that your panels are not giving you (remember that they are producing 4 kW).

What happens with the annual maintenance? Good news: Panels tilted at more than 10 degrees will clean themselves in the rain and have no moving parts to clean. But if you experience periods of drought, the system can become excessively dirty. You also have to take into account periods of haze (desert sand in the atmosphere). In these cases, you can gently clean the system without damaging the plate glass, with water (from a hose for example).

Important to know what happens if you don't have a perfect sunny day!

⛅ On cloudy days: the system continues to produce energy. The panels can still produce 10-25% of their typical output on a cloudy day. Clouds can reflect or even magnify sunlight, generating additional energy output from the system.

🌦️ On rainy days: the system also produces energy. Rain clouds block sunlight, but about 10% of its typical output can still be expected. In addition, as we have seen, rain provides a cleaning to the system. Only a few days of rain a year are enough to clean it.

❄️ In winter, although temperatures drop and there are fewer daylight hours, the Sun rises every month of the year regardless of the season and the system works thanks to the sunlight obtained, not heat.

6. Maximise your savings with your solar system

What do you think, is it a good idea to use electronic devices during the day when you can take advantage of the energy of the sun present? Absolutely! Because you save yourself from paying a figure for each kWh consumed from the network to your supplier (say, for example, €0.225/kWh, which is equal to €225/MWh).

In addition, you only earn €0.05/kWh for exporting your excess energy to the grid, on average, since it depends on each particular company. This is the concept of surplus compensation (hyperlink from the beginning). Therefore, it is clearly more valuable that you self-consume your own generation from your plates. The surplus energy that you do not consume will be fed into the network and you will receive financial compensation for it. For example:

Invoice summary

Contracted power                                                €12.28

Energy consumed                                                €7.95

Surplus energy                                                      -€5.12

Electricity tax                                                        €0.77

Measurement and control equipment rental     €0.74

Normal VAT (21%)                                                €3.49

Total invoice amount                                             €20.11

If you still continue to sell your surplus to the network, and add your savings from not buying from the network for your self-consumption, this translates into pure savings thanks to solar energy!

The more solar energy you self-consume, the lower your electricity bills will be and the faster you will recover your investment. With a solar system in your home and connected to the network, you would pay your marketer:

Consumption (variable) – Export of your solar surplus + Fixed charge = Total of your new bill

We named the result as "total of your new bill" because before having a solar system in your home, the total of your bill was made up of the following elements:

Consumption (variable) + Fixed charge = Total of your bill

Let's calculate in an example, the savings of a bill with a solar system and one that does not:

Assuming that there is no solar self-consumption system:

  • The fixed term (contracted power, access toll, marketing margin) = €20
  • The variable term (energy consumed, energy cost, access toll) = €45
  • Meter rental and electricity tax = €5
  • VAT (21%) = €15
  • Total invoice = €85

In the case of having a solar energy system:

  • Fixed term = €20
  • Variable term (lower network energy consumption and with compensation for surpluses) = €13
  • Meter rental and electricity tax = €2.5
  • VAT (21%) = €7.5
  • Total invoice = €43

The savings on the electricity bill with self-consumption (€43) compared to the bill without self-consumption installation (€85) reaches 50%. Remember that the costs of the fixed part of the power, meter rental, social bonus and taxes must be taken into account on the invoice.

In addition, if we assume another example, in which the cost of the system has been €12,000 and the system helps you save €2,000 per year on electricity bills, the recovery period will be about 6 years:

€12,000 / €2,000 per year = 6 years

In addition to these savings, there are bonuses with which you can make your self-consumption installation profitable and save up to 50% of the IBI (Real Estate Tax) for 5 years and 95% of the ICIO (Construction and Installation Tax), depending on each Town Hall. In addition, at the national level, the Government has extended in 2022, 650 million euros the aid from the European Funds (NextGeneration EU) destined for solar self-consumption.

‼️ Important!

  • To use the energy of your system efficiently and save money, you can collect your daily consumption during the hours when the Sun is present and your system is working.
  • With your solar system you can save approximately 60% and up to 70% on your electricity bill (in the variable part of it, referring to electricity consumption).
  • Depending on the city, you can recover the investment between 5 to 8 years, depending on your consumption and -among other factors- on whether you have had the discounts and subsidies or not.

You can see more about the return on investment and amortisation of a solar system in your city here.

3: Storage 🔋

Everything you need to know to understand about storage batteries for solar systems 😊

If you install a battery in your house, instead of consuming and buying electricity from the conventional grid, you would use the solar energy generated by the panels and stored, whenever possible. Also, if you have a battery in your home, you can configure it to back up your home in the event of an emergency or blackout.

The world of storage brings with it some frequently asked questions that many people like you ask themselves to understand if, for example, it is worth buying batteries now or later; if they are really necessary and how expensive they can be; how much savings will be generated by using the storage; how advanced battery technology is; what guarantees do they have; and if there are aids or incentives for those who wish to acquire them for their homes.

In this section we present all the answers to these questions. Let's get to it and start this journey into the world of batteries!

1. Battery operation

A battery is made up of two electrodes, one negative and one positive, a separator to prevent short circuits, and an electrolyte that allows the flow of electrons. In a few words, it is a box that, when connecting the positive and negative, is charged and discharged, just like it happens with your mobile and computer.

  • The batteries are discharged at night, when there is no longer any production from the solar system and during periods of the day when the production of the panels is not sufficient to meet the demand for electricity consumption.
  • Batteries are charged in energy surpluses, when system production is higher than consumption. Thus, when the Sun is gone, you make sure that the battery is charged as much as possible to use and self-consume that stored energy.

How batteries work in a solar system.

2. Current technologies

Advances in lithium-ion technology have resulted in lithium-ion batteries dominating the market for several reasons:

  • Superior performance - better power output and depth of discharge
  • Maintenance free operation
  • longer warranties
  • Competitive prices
  • Smaller and lighter

The two main lithium ion technologies are Nickel Manganese Cobalt (NMC) and Lithium Iron Phosphate (LiFePO4).

3. Cost it adds to the solar system

This will always depend on the size of the system and the consumption that the battery needs to store. Even so, to give you an approximate answer, the installation of a battery within your solar system will add a cost of between €4,000 to €5,000, and will allow you to increase the savings on your electricity bill from €500 to €800 per year (and even more) as the price of electricity continues to rise.

Even so, in the event of a blackout for example, most batteries will not support the entire house, only some circuits of it. Most reasonably priced battery systems simply cannot keep the home running normally during a power outage for two main reasons: either there is not enough power or there is not enough power.

4. Understanding the moment in which the batteries are

In general, home batteries currently do not pay for themselves before their warranty expires (neither financially nor environmentally) which is typically 10 years. This is why it is advisable to wait for the economy of the batteries to improve before buying them.

However, at some point in the near future, home batteries will make economic and environmental sense (just as solar panels do today). This means that sometime in the next three to ten years, batteries will be as cheap that it would be crazy not to have them at home.🤯

5. Incentives

As we have seen, subsidies from European funds are part of the Recovery, Transformation and Resilience Plan and in the specific case of wanting to incorporate batteries into an existing solar system, the subsidy will be between €140 and €490/kWh.

4: Electric vehicles 🚗🔌

If your ultimate goal is to have a home that is fully integrated with energy storage and electric vehicles, this section is for you 🤩

Charge your electric car with solar energy! The easiest way to charge an electric car with your solar system is to plug the car in during the day when the sun is shining. In case the amount of solar power generated is greater than the amount you need to charge the car, this will be used by other devices and appliances and you will not need electricity from the grid. In contrast, if the amount of solar power generated is less than what your car and other household loads need, you will use grid power to make up the shortfall.

📌Note: If you are not clear about the difference between a kilowatt (kW) and a kilowatt-hour (kWh), we recommend reading our section first “Difference between solar energy and solar power”. 😏

Just as for gasoline cars, the measurement of litres per 100 km is the amount of fuel that it will consume on average to travel 100 km, EVs also have a similar measurement: kWh per km. This varies from EV to EV, but on average most electric cars will get around 6 km of range with 1 kWh of electricity in their battery pack.


When sizing a solar energy system for an electric vehicle, there are a number of factors to think about such as: the model of the electric car (and its specifications); the average distance travelled and driving habits of those who will use the car; home energy consumption; and if you plan to add storage batteries or more EVs in the future.

1. Batteries to charge the electric vehicle: yes or no?

The use of storage batteries to charge the electric car at night is not currently the best option. While you could charge a home battery system during the day with solar energy and then charge an EV at night with this stored energy, this kind of heavy use will shorten the life of the solar battery (although the technology is improving in this sense).

Also, the losses that we mentioned a moment ago accumulate between the solar panels and the home battery, and then from the home battery to the EV load. The best then at present, is to take advantage of the hours of Sun during the day to charge the car.

2. Types of electric vehicle chargers

If you are building a new home, consider a three-phase electrical connection. It will allow you to install a larger solar system to supply future high electricity needs (home batteries and electric vehicles).

Electric car chargers are divided into three levels, where level 1 is the slowest way to charge and level 3 is the fastest. Let's see them below:

  • ⚡Level 1 charging is the slowest rate (max 3 kW: 5 to 20 hours) that typically uses a standard 10 amp power point. It is the most basic charge and allows to increase the useful life of the batteries. Its cons is that the loading time is long.
  • ⚡⚡Level 2 charging requires the installation of a specialised EV charger (semi-fast charging 3 kW-22 kW: 1 to 4.5 hours). They can be found in parking lots of shopping centres, companies or on public roads. An example of these are the Wallbox chargers.
  • ⚡⚡⚡Level 3 charging is fast charging (up to 150 kW: 5 to 30 minutes). It is the fastest type of charge, but also the most expensive, normally used by people who travel long distances, since they can add up to 720 km of range per hour. The best known example of a level 3 charger is the Tesla SuperCharger.


Since solar systems have a percentage of inefficiency (panels, inverters and EV batteries), it would be normal to expect load losses of more than 10%. This means that if your solar panels generate 1 kWh of energy, only 900 Wh will end up as energy in an EV battery pack. For this reason, it is advisable to install more solar panels than are needed to compensate for these load losses in the systems.

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In addition, if you also want to contribute your bit in the transition towards clean energy for a healthy and habitable planet for future generations, from Quiero Sol we help you to obtain instant photovoltaic quotes that you can compare before buying your solar products or hiring one. installation company.

Cheers to our planet!

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