If you prefer to always view the website in English, please click here.
How many solar panels your house needs
The number of solar panels that a home needs varies between 4 and 18 photovoltaic panel modules. To opt for more or fewer panels to make the investment of the installation profitable will depend on the annual electricity consumption for the house.
The following table will provide some guidelines for the number of modules depending on the type of consumption for the house.
Number of solar panels according to your annual consumption
| Annual consumption | Number of solar panels | Consumption profile |
|---|---|---|
| < 2000 kWh | 2 - 4 | Low |
| 2000 - 4000 kWh | 4 - 6 | Medium - low |
| 4000 - 6000 kWh | 7 - 9 | Medium |
| 6000 - 8000 kWh | 10 - 15 | Medium - high |
| 8000 - 10000 kWh | 16 - 20 | High |
Is it cost-effective to install solar panels at home?
In Spain, we enjoy an average of 2,500 hours of sunshine per year. This makes us one of the sunniest countries in Europe, along with Turkey, Italy, Greece, France, and Portugal.
In addition to offering excellent conditions for its development, solar energy is one of the most highly valued forms of energy in our country. According to the Spanish Observatory of Photovoltaic Self-Consumption, 87.9% of users prefer solar energy over wind (60%), hydropower (12.9%), and energy from organic waste (11.2%).
The reality is that solar photovoltaic generation in Spain has been constantly growing since 2010. In 2021, the installed capacity of ground-mounted plants reached 3.5 GWp, a 21% increase compared to the previous year. Self-consumption, in turn, grew by 102% in 2021 compared to the year before, reaching 1,203 megawatts installed. By sector, household self-consumption increased by 32%, while commercial grew by 26% and industrial by 41%, according to data from the Spanish Solar Photovoltaic Association (UNEF).
Advantages of solar energy
But is it cost-effective to install solar panels at home? The answer is yes. In fact, one of the main reasons consumers choose this type of energy is the savings on their electricity bills. According to data from the 3rd Spanish Observatory of Photovoltaic Self-Consumption, these savings range between 30% and 80%. In addition, there are tariffs that allow you to sell the surplus solar energy you generate, helping you save even more.
Some of the advantages of solar energy are shared with other renewable sources. The most important benefit, of course, is that it helps to fight climate change, as it does not emit GHG. However, the profitability and payback period of solar panels are among the main reasons why more and more people are switching to self-consumption.
“With solar panels, bill savings range between 30% and 80%”.
A decisive factor in the payback of solar panels is their low maintenance requirements and long lifespan. Panels can last between 20 and 25 years. Throughout their useful life, they only require occasional cleaning, insulating rubber inspections, and general upkeep.
This durability is largely thanks to the advanced technology behind them. This technology is remarkably silent, making it ideal for residential installations.
And last but not least: solar panels are sustainable all the way through. At the end of their useful life, they can be recycled and reused, further reducing the environmental impact of this technology.
Disadvantages
Although there are many advantages, there are still some barriers to photovoltaic self-consumption. The main one is the significant upfront investment required.
While prices have dropped in recent years, a photovoltaic self-consumption system for a single-family home may still require an initial investment of between €5,000 and €8,000. However, it’s important to note that there are subsidies available, and it is an investment that usually pays for itself in about 7 to 8 years.
Owners of single-family homes are not the only ones who can make this investment and benefit from these subsidies. Solar panels can also be installed in residential communities. Shared or collective self-consumption allows any apartment building to produce and consume its own electricity by installing this technology, normally on the roof.
Another drawback is that, as explained, this energy comes from the sun. This means that although it is inexhaustible, it is also variable. As it depends on sunlight, it fluctuates with the seasons and local cloud coverage. Obviously, it doesn’t work at night, which means energy production is intermittent.
Therefore, to fully benefit from solar self-consumption, it is important to install batteries that store energy for use when the sun isn’t shining. Installing these storage systems is still quite costly. Even so, solar energy and photovoltaic panels are becoming more affordable. Simultaneously, new solutions —such as virtual battery storage— are emerging as a strong ally of energy self-consumption in Spain.
What factors influence the number of solar panels a home needs?
Although the consumption you make is essential to be able to determine the size of the photovoltaic installation for our house, there are other factors that it is also important to take into account when calculating the number of solar panels.
- Annual consumption for the house.
- Quality and performance of the panels.
- Type of solar panel.
- Installed capacity.
- Orientation of the roof.
- Geographical location.
1. Annual electricity consumption
You can use your last bill to make a quick estimate of your annual consumption. For example, if the bill is for two months, you just multiply the total kWh consumed by 6. If you receive an invoice every month you should multiply by 12.
However, as electricity consumption is often not the same in all months of the year, you can go to the client area to find out exactly what your annual consumption is in kWh.
2. Quality and performance of photovoltaic panels
The quality of the panels is essential for their performance when it comes to producing energy. If the system is better quality it will cost a little more However, it will make better use of the sunlight and be able to produce more electricity.
If you choose the solar panels for your home well this will enable you to reduce the number of solar panels you need to install. Furthermore, solar panels with a higher performance will enable you to recover the investment in the installation faster.
It is always advisable to use panels from manufacturers with more experience and a good reputation in the production of photovoltaic panels.
3. Type of solar panel according to cell type
Performance is the ability of the panel to produce electricity when sunlight strikes it. The technology used to manufacture the cells contained in the photovoltaic panel will affect its performance, and there are essentially three types of panels.
| Type of solar panel | Performance |
|---|---|
| Monocrystalline | 16 to 23% |
| Polycrystalline | 15 to 19% |
| Amorphous | 8 to 12% |
Crystalline panels (poly- - and mono-) give the best results in performance and are currently used for the installation of photovoltaic panels in homes. Amorphous panels are cheaper but are currently in disuse due to their low performance and shorter useful life.
4. Installed capacity
The capacity of the solar panels will indicate the amount of electricity that your domestic installation is capable of producing. Power is usually indicated in units of Wp (peak power in Watts). So the total power for the installation is the sum of the power for all the panels of which it is made up.
Number of panels * power for each panel (Wp) = Installation power (Wp)
For example, an optimal solar panel has a power of 300 Wp. If your installation consists of 6 solar panels you have a total power of 1800 Wp. This power value corresponds to 1800 kWh of electricity annually under theoretical conditions.
It should not be forgotten that the WP value indicated by the manufacturers is measured under optimal conditions of solar radiation (Solar radiation = 1000 W/m2 and Temperature = 25°C). Therefore, to correctly calculate how many panels your house needs, you also need to make a study of both the orientation of the installed surface and the geographical location of your home.
5. Orientation and inclination of the roof
In Spain, the optimal orientation for solar panels is towards the south. This is the orientation that best takes advantage of solar radiation for the production of electricity in a domestic self-consumption installation.
There is no need to worry if you cannot have that exact orientation. In the case of orientations towards the southeast or southwest, the loss of efficiency is only between 1% and 4% which is perfectly acceptable.
For east- and west-facing orientations, efficiency loss can reach 20% to 30%, which means more panels may be needed to reach the required production capacity. For north-facing orientations, it is important to conduct a very thorough preliminary study to assess whether installing panels is worthwhile.
As for tilt angle, calculating how many solar panels are needed will be slightly more limited due to the building structure. Still, panels are installed on their own supports to ensure the optimal tilt angle.
Generally, the optimal inclination when installing solar panels on a house depends on the latitude of the locality.
Table to calculate the angle of solar panels on a house
| Season | Angle of inclination for the solar panel |
|---|---|
| Winter | 29 degrees+ (latitude * 0.9) |
| Spring and autumn | Latitude - 2.5 degrees |
| Summer | (Latitude * 0.9) – 23.5 degrees |
For example, the city of Toledo is at a latitude of 39.8568. If you multiply this by 0.9 you get a value of 35.87112. So the optimal inclination angles for the solar panel system would be: 64.9 degrees in winter, 37.4 degrees in spring/autumn and 12.4 degrees in summer.
Modifying the inclination of the installation is an complex and expensive process, usually, in the studies prior to installation an angle of inclination for the panels is selected that works optimally during all seasons of the year.
6. Geographical location of the house.
When calculating how many solar panels a house needs, it is essential to take into account the geographical location of your house. In Spain each province receives a different amount of solar radiation so, depending on the area in which you live, you will need to install more or fewer solar modules.
For example, in the province of Málaga the average value for the energy produced throughout the year is 1700 kWh per m2, while in the province of Lugo it is 1270 kWh per m2. So in Lugo you would need between 1 and 3 additional modules to produce the same energy as in Málaga.
It is generally recommended to request a customised study to ensure that the installation of solar panels in your home fits your energy needs taking all these factors into account.
Restrictions on the number of solar panels on a house
Square meters available
With the new more efficient solar panels, the surface area of the roof or where you intend to install the solar panels is not usually a limiting factor.
However, it is important to bear in mind that if you want to produce a large amount of energy you may be limited by the available surface area. In those cases it is better to have panels with higher power that generate more energy in the same number of square metres.
Hours of sunshine versus hours of consumption
The hours around the middle of the day, when there is greater light intensity, are the hours when more energy is produced by your solar panels. If those hours coincide with the hours where you make the highest consumption of electricity, you will get the most out of your installation.
However, if you need to consume more energy at another time of day, a traditional panel system may not be as cost-effective. In this case, there are two solutions:
- To install an electric accumulator: these devices store the excess electricity generated by your solar panels so you will be able to use it at another time. These are currently expensive devices with a short life cycle, so they are not recommended unless you are prepared to make a large investment.
- Compensation mechanism: there are electricity tariffs that compensate for a surplus of energy generated by solar panels and the corresponding amount is discounted from the bill. All the electricity you use in the hours when your solar panels are not producing is offset by the energy you do not use when they are producing electricity, so you make a saving on your bill.
In single-family homes, it is generally advisable to take advantage of this compensation mechanism to make the most of energy production from solar panels.
How much does a photovoltaic installation cost depending on the number of panels?
Currently the price of a photovoltaic electrical installation for a house is between €0.8 per kWh and €1.2 per kWh of annual electricity consumption. This is approximately between €500 and €600 per solar panel or module for the complete installation.
| Annual consumption | Number of panels | Price for the installation |
|---|---|---|
| 3300 kWh | 6 | 4000€ - 5000€ |
| 5000 kWh | 9 | 5000€ - 6000€ |
| 6600 kWh | 12 | 6000€ - 7000€ |
| 9900 kWh | 18 | 7000€ - 10000€ |
As always, these prices are just a guideline and it is best to request a customised study in accordance with your needs. Furthermore, the prices do not include any possible discounts or subsidies which may be applicable in the different plans that exist to promote the use of clean energies.
Guarantee and extras included in the price
When calculating how many panels you need for your home and how much they will cost, you also need to take into account other expenses that may or may not be included in the final cost for the installation. The number of years of guarantee is also a very important factor to take into account, as it could mean the difference between whether or not future cost overruns may appear.
Take a minute to find the product that best suits you:
{{firstStep.title}}
Take a minute to find the product that best suits you:
{{title}}
{{content.phone.title}}
{{content.phone.text}}
{{content.phone.phoneText}}
{{content.form.title}}
{{content.form.text}}
{{content.form.success.title}}
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.
Take a minute to find the product that best suits you:
{{title}}
{{content.phone.title}}
{{content.phone.text}}
{{content.phone.phoneText}}
{{content.form.title}}
{{content.form.text}}
{{content.form.success.title}}
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.
Comparison of Electricity and Gas Tariffs
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.
Do you want to see all our offers?
Spend a minute to find the product which best adapts to you:
{{firstStep.title}}
Spend a minute to find the product which best adapts to you:
{{title}}
Spend a minute to find the product which best adapts to you: