Choosing the right power for your solar panels is an important step for any household that wants to save energy. It’s important to understand how it works so that the installation is useful. This article will give you information to help you choose the right solar panel power, depending on what you need and your home. We’ll look at the important points together to make your solar project a success.

Key Points

• The power of a solar panel is measured in Watt-peak (Wp) or kilowatt-peak (kWp). These units show the maximum production in perfect conditions. The actual production depends on several things, such as sunshine and temperature.
• To find out what solar panel power you need, look at your annual electricity consumption. The size of your house, the number of people who live there and your habits with electrical appliances matter a lot.
• Several factors influence the choice of power: your budget, the space available on your roof, and what you want to do with the electricity (consume it yourself or sell it).
• Calculating the number of solar panels needed requires estimating the desired power. For a house of 100 m², we often talk about 3 kWp, which represents about 8 panels of 400 Wp. This is an estimate, a personalised study is always better.
• For your solar panels to be effective, you need to pay attention to the orientation and inclination of your roof. Temperature and shaded areas (trees, buildings) can also change energy production.

Understanding the power of a solar panel

Definition of peak power (Wp and kWp)

The power of a solar panel is a determining factor in the choice of your installation. It indicates the amount of energy that the panel can produce in optimal conditions. This measure is expressed in watt-peak (Wp) or kilowatt-peak (kWp). Peak power represents the maximum electrical power that a photovoltaic solar panel can provide in ideal conditions. It is important to note that these conditions are rarely achieved in reality, but this value serves as a reference for comparing different panels. A solar panel electric car: guide to sizing your installationguide can help you understand how to size your installation.

Impact of power on electricity production

The power of a solar panel directly influences its electricity production. A more powerful panel will generate more electricity over a given period. For example, a 400 Wp panel will produce more electricity than a 300 Wp panel in the same sunshine conditions. It is therefore essential to choose a power adapted to your energy needs. The power of a solar panel solar panel is a primary criterion for choosing your solar installation.

Consider these points:

• A 1 kWp panel in Lille produces approximately 900 kWh per year.
• In Paris, the same installation generates approximately 1000 kWh per year.
• In Bordeaux, production can reach 1200 kWh per year.

Factors influencing real power

Several factors can affect the actual power of a solar panel. The ambient temperature, the orientation and inclination of the panel, as well as shading, play a crucial role. Solar panels for self-consumption without resale solar panels have a power unit between 375 and 500 Wp, allowing to produce between 300 and 750 kWh per year. In addition, the quality of the material and its aging can lead to a loss of power over time. It is therefore important to take these elements into account to optimise the performance of your installation.

It is important to differentiate between the nominal power, which represents the theoretical maximum capacity of a solar panel, and the actual power, which reflects reality more closely. The actual power is always lower than the peak power, because ideal conditions are never met.

Evaluate your energy needs to choose what solar panel power

It is essential to accurately assess your energy needs before determining the power of your solar installation. This step will allow you to correctly size your system and optimise your investment. Several factors must be taken into account for an accurate assessment.

Analysis of annual electricity consumption

The first step is to analyse your annual electricity consumption. To do this, examine your electricity bills from previous years. Identify periods of high consumption (winter, summer) and the most energy-intensive appliances. This analysis will give you a clear idea of your base consumption and peak demand. You can also use an online simulation tool to estimate your future consumption based on your equipment and habits.

Influence of household size and living area

The size of your household and the area of your home have a direct impact on your energy consumption. The higher the number of occupants, the higher the consumption. Similarly, a large house will require more energy for heating, air conditioning and lighting. It is therefore important to take these elements into account to adapt the power of your solar installation. The size of your house is a determining factor.

Taking into account consumption habits and equipment

Your consumption habits and the equipment you use play a crucial role in determining the power required. If you work remotely, use energy-intensive appliances (air conditioning, heated swimming pool), or have specific needs (electric vehicle), your consumption will be higher. It is therefore imperative to assess the impact of these elements on your overall consumption. For self-consumption without resale, it is advisable to calculate your needs finely using your Linky meter and a wattmeter.

It is important to note that the power of solar panels decreases over time, on average by 0.5% per year. In addition, external factors such as shading caused by tree growth can also affect energy production. It is therefore essential to take these elements into account when assessing your energy needs.

Here are some examples of equipment and their impact on consumption:

• Electric heating: very energy-intensive, especially in winter.
• Air conditioning: high consumption in summer.
• Household appliances (washing machine, tumble dryer, dishwasher): variable consumption depending on the frequency of use.
• Lighting: favour LED bulbs to reduce consumption.

In summary, an accurate assessment of your energy needs is essential to choose the appropriate power for your solar installation. Do not hesitate to call on a professional for a personalised thermal assessment.

Choice criteria to determine what solar panel power

The budget allocated to the photovoltaic installation

The budget is a determining factor in the choice of the power of your solar installation. It is important to define a realistic financial envelope before starting your project. The cost of solar panels varies depending on their power, technology and brand. Do not forget to include in your budget the costs of installation, connection to the grid and any administrative procedures. It is possible to find solar panels at the right price by comparing offers.

The space available on the roof

The surface of your roof directly influences the maximum power you can install. Each solar panel has a standard size, and the total power of your installation will depend on the number of panels you can physically install. You must also take into account the orientation and inclination of your roof, as they affect the performance of the panels. A roof well exposed to the sun will optimise electricity production. It is important to note that a solar panel is approximately 1.8 m². Thus, the size of your roof is an important factor in estimating the yield.

The objective of the installation: self-consumption or resale

The objective of your solar installation is an essential criterion for determining the necessary power. If you opt for self-consumption, that is, you consume the electricity produced by your panels, the power of your installation must be adapted to your energy needs. If you want to resell part or all of the electricity produced, you can consider a more powerful installation. It is important to define your objective before choosing the power of your solar panels. If you want to install photovoltaic solar panels to produce a maximum of renewable energy, you will move towards a power between 3 and 9 kWp.

Determining the ideal power for your solar panels requires an in-depth analysis of your needs, your budget and the constraints of your home. Do not hesitate to call on a professional to assist you in your project and advise you on the solution best suited to your situation.

Here are some points to consider:

• Your annual energy needs
• The surface available on your roof
• Your budget
• The objective of your installation (self-consumption or resale)

Calculate the number of solar panels needed

Estimation of the desired solar power

To determine the number of solar panels you need, it is essential to estimate the solar power you want to install. This power, expressed in watt-peak (Wp) or kilowatt-peak (kWp), represents the maximum power that your installation can produce in optimal conditions. The desired solar power depends directly on your annual electricity consumption and your objectives in terms of self-consumption or resale of electricity.

To estimate this power, you must take into account several factors:

• The size of your household (number of people living in the home).
• The area of your home.
• Your electricity consumption habits (what appliances do you use and how often?).
• Your geographical location (sunshine varies considerably from one region to another).

It is important to note that peak power is a theoretical value. The actual production of your solar panels will depend on many factors, such as the orientation and inclination of your roof, weather conditions and the presence of shading.

Example for a house of 100 m²

Let’s take the example of a house of 100 m². In general, it is estimated that such a house requires a solar installation of approximately 3 kWp. Knowing that a standard solar panel has a power of approximately 400 Wp, it would therefore take approximately 8 solar panels. However, this figure is only an estimate.

Region	Annual consumption (kWh)	Number of panels (estimate)
Lille	3 200	8
Nantes	3 600	9
Bordeaux	3 750	10
Marseille	4 650	12

It is crucial to carry out a personalised simulation to obtain an accurate estimate of the number of solar panels needed for your home. This simulation will take into account the specificities of your situation and will allow you to optimise your installation.

Importance of a personalised simulation

Although general estimates can give an idea of the number of panels needed, a personalised simulation is essential for several reasons:

1. Accuracy of the estimate: A simulation takes into account data specific to your situation, such as the weather history of your region, the technical characteristics of the solar panels and the details of your house (orientation, roof inclination, shading).
2. Optimisation of the installation: A simulation allows to optimise the orientation and inclination of the panels to maximise electricity production.
3. Adequacy with your needs: A simulation ensures that the installation is perfectly adapted to your energy needs and your objectives (self-consumption, resale).
4. Profitability: By optimising electricity production, a simulation helps to improve the profitability of your solar installation. Solencia, for example, offers services for the installation of solar panels and can help you to carry out an accurate simulation.

Optimise the performance of your solar installation

To get the most out of your solar installation, it is essential to consider several key factors. Adequate optimisation can significantly increase energy production and, consequently, reduce your electricity bill. It is not enough to install panels, they must be installed correctly and maintained.

The orientation and inclination of the roof

The orientation and inclination of your roof play a determining role in the performance of your solar panels. A south-facing orientation is generally ideal in the northern hemisphere, as it maximises exposure to the sun throughout the day. However, a slight deviation to the east or west may also be acceptable, especially if it allows for a better distribution of energy production over the day. The optimal inclination varies depending on your latitude, but is often between 30 and 40 degrees. A correct inclination allows to capture the maximum of solar radiation, especially during the winter months when the sun is lower in the sky. It is important to note that the ideal orientation and inclination may vary depending on your geographical location and local climatic conditions. For an installation in the La Rochelle region, it is important to consider the installation facing the ocean.

The impact of ambient temperature

Solar panels, although they capture energy from the sun, are sensitive to temperature. Paradoxically, too high a temperature can reduce their efficiency. Photovoltaic cells operate optimally at moderate temperatures, generally around 25°C. Above this temperature, their performance decreases. To mitigate this effect, it is advisable to opt for an installation that promotes ventilation of the panels, such as a superimposed installation. This allows to dissipate heat and maintain the panels at a temperature closer to their optimal operating range.

The management of shaded areas

Shading, even partial, can have a significant impact on the energy production of your solar panels. A simple tree, a chimney or even a cable can cast a shadow on part of your panels and significantly reduce their performance. It is therefore crucial to identify and minimise potential shaded areas before installation. If shading is unavoidable, there are solutions, such as the use of power optimisers or micro-inverters, which allow to maximise energy production even in case of partial shading. These devices isolate the panels affected by the shade from the rest of the installation, thus avoiding a drop in overall production. A careful analysis of shaded areas is therefore essential to guarantee optimal energy production. It is important to consider the key factors to develop a photovoltaic park project.

It is important to regularly monitor your solar installation to detect any potential problems, such as the accumulation of dirt or debris, which could reduce its performance. Periodic cleaning of the panels can help maintain their optimal efficiency. In addition, it is advisable to have your installation checked by a qualified professional at least once a year to ensure that it is functioning correctly and safely.

The different types of installations and their power

There are a variety of solar installations, each designed to meet specific needs. The choice will depend on your main objective: reducing your electricity bill, generating additional income, or a combination of both. It is important to understand the different options to make an informed choice.

Solar panels for self-consumption without resale

Self-consumption without resale is a simple approach: you use the electricity produced by your solar panels to directly power your home. The main objective is to reduce your dependence on the electricity grid and reduce your energy bill. This option is particularly interesting if your electricity consumption is high during daylight hours. For a well-insulated house, a residential air conditioning installation can be a good investment.

• Reduction of the electricity bill.
• Partial energy independence.
• Quick and easy installation.

Installations for the sale of surplus or all

If you produce more electricity than you consume, you can sell the surplus to the electricity grid. In some cases, you can even choose to sell all of your production. This option can generate additional income, but it involves more complex administrative procedures. It is important to assess the profitability of the investment, as the power of the installation must not be at the expense of the profitability of the project.

The sale of surplus is an interesting option if you have a large roof area available and good exposure to the sun. However, it is important to note that the income generated by the sale of electricity is taxable if the power of your installation exceeds 3 kWp.

Solutions for small spaces or specific needs

Solar panels are not reserved for large houses with sloping roofs. There are solutions for small spaces, such as balconies or gardens, as well as for specific needs, such as powering a camper or a boat. Flexible solar panels are an interesting option for these applications.

• Solar kits for balconies.
• Portable solar panels for camping.
• Customised solutions for specific needs.

Technical considerations for what solar panel power

The power loss of panels over time

It is important to understand that solar panels do not retain their initial power indefinitely. Over the years, natural degradation occurs, leading to a gradual decrease in their production capacity. This power loss is generally estimated at approximately 0.5% per year, although this figure may vary depending on the quality of the panel and environmental conditions.

• The quality of the materials used in the manufacture of the solar panel directly influences its durability and resistance to degradation.
• Extreme climatic conditions, such as high heat or significant temperature variations, can accelerate the degradation process.
• Regular maintenance, including cleaning the panels, can help minimise power loss.

It is therefore essential to take into account this predictable power loss when sizing your solar installation. A slightly oversized installation at the start can compensate for this degradation and guarantee sufficient energy production in the long term.

The importance of the quality of the material

The quality of the material is a determining factor for the performance and durability of your solar installation. Opting for solar panels from recognised brands, certified and manufactured according to rigorous standards is a wise investment. Higher quality panels generally offer better performance, a longer lifespan and increased resistance to harsh environmental conditions. It is important to note that photovoltaic solar panels are a long-term investment.

• Check the certifications of solar panels, such as the IEC standards, which guarantee their compliance with quality and safety standards.
• Find out about the manufacturer’s reputation and the reliability of its products.
• Compare the technical data sheets of the different panels to evaluate their performance, their temperature tolerance and their resistance to weather.

The guarantees associated with photovoltaic panels

The guarantees offered by solar panel manufacturers are an important indicator of the confidence they have in their products. They protect the buyer against manufacturing defects and premature performance declines. There are generally two types of guarantees: the product guarantee and the performance guarantee. The product guarantee covers manufacturing defects for a specified period (generally 10 to 12 years). The performance guarantee ensures a certain level of electricity production after a certain number of years (for example, 80% of the initial power after 25 years). It is crucial to fully understand the terms and conditions of these guarantees before making your choice. Solencia specialises in the photovoltaic future.

• Carefully examine the duration and conditions of each type of guarantee.
• Check if the guarantee is transferable in case of sale of your property.
• Keep all documents relating to your solar installation, including the guarantee certificates, as they will be necessary in case of a claim.

In summary, to choose the solar panel power best suited to your needs, it is imperative to take into account the natural degradation of the panels, to favour the quality of the material and to fully understand the guarantees offered. A rigorous and informed approach will allow you to maximise the performance and durability of your solar installation. Do not hesitate to call on a professional to carry out a personalised solar quote.

Procedures and authorisations for installation

The installation of solar panels, although beneficial for the environment and your wallet, requires following certain administrative procedures. It is important to inquire with the competent authorities before starting your project.

Regulations for individual dwellings

For an individual house, the first step is to check with your town hall if your project is subject to a prior declaration of works or a building permit. In general, a prior declaration is sufficient for roof installations that do not significantly modify the exterior appearance of the building. However, if your home is located in a protected area (classified site, protected sector), the rules may be stricter and a building permit may be required. It is therefore imperative to consult the Local Urban Plan (PLU) of your municipality.

It is advisable to submit your application for a prior declaration or building permit before purchasing the equipment. This will avoid disappointments if your project is refused. Do not hesitate to contact the town planning department of your town hall for personalised advice.

Necessary agreements in co-ownership

If you live in a co-ownership, the installation of solar panels is subject to the agreement of the general meeting of co-owners. You must present your project at a general meeting and obtain a favourable vote. The co-ownership regulations may also contain specific clauses regarding the installation of solar panels, particularly with regard to aesthetics and architectural integration. It is therefore essential to consult this document before submitting your project.

Here are the steps to follow:

1. Inform the trustee of your project.
2. Request the inclusion of your project on the agenda of the next general meeting.
3. Prepare a complete file presenting the technical characteristics of the installation, its aesthetic impact and the expected benefits.
4. Obtain a favourable vote from the general meeting.

Prior declaration of works

The declaration of works is a mandatory administrative formality in most cases. It allows the town hall to verify that your project complies with the town planning rules in force. The prior declaration file must include:

• A Cerfa form n°13703*07 duly completed.
• A site plan of the land.
• A mass plan of the construction.
• A roof plan indicating the location of the solar panels.
• A description of the materials used and their exterior appearance.
• Photographs of the initial state of the building and its environment.

The processing time for a prior declaration is generally one month. In the absence of a response from the town hall within this period, your application is considered tacitly accepted. However, it is preferable to obtain written confirmation from the town hall before starting work. For ecological agriculture projects, photovoltaic greenhouses can be an interesting solution, but local regulations must also be respected.

Professional support for your solar project

Switching to solar energy is an important project, and it’s perfectly normal to feel a little lost at first. Fortunately, many professionals are there to support you at every stage, from planning to commissioning your installation. They can help you correctly size your installation, choose the right equipment and carry out the necessary administrative procedures.

The interest of a thermal assessment

Before embarking on the installation of solar panels, it is strongly recommended to carry out a thermal assessment of your home. This diagnosis will accurately assess the energy needs of your household and identify any heat losses. An accurate thermal assessment is essential to determine the power of the solar panels needed and optimise the performance of your installation. It will help you avoid oversizing or undersizing your installation, which could lead to unnecessary costs or insufficient energy production.

Request several quotes for an informed choice

It is crucial not to rush and to compare the offers of different installers. Request at least three detailed quotes to be able to compare prices, types of panels offered, guarantees offered and services included. A quote must clearly mention the power of the panels, the cost of installation, the costs of connection to the grid and any financial aid to which you may be entitled. Do not hesitate to ask questions to the installers to clarify the points that seem obscure to you. This will allow you to make an informed choice and find the offer best suited to your budget and your needs.

Simulation tools to estimate power

Many online simulation tools can help you estimate the power of solar panels you need. These simulators take into account different parameters such as the geographical location of your home, the orientation and inclination of your roof, your annual electricity consumption and the type of solar panels considered. These tools can give you a first estimate, but it is important to supplement it with the advice of a professional. An expert will be able to refine the calculation by taking into account more specific factors, such as shaded areas or local climatic conditions. Some suppliers such as EDF offer solutions for professionals, including personalised simulations.

Profitability and energy savings with solar panels

Reduction of the energy bill

The installation of solar panels represents an initial investment, but it quickly translates into a significant decrease in your electricity bill. By producing your own energy, you reduce your dependence on the traditional electricity grid and fluctuations in energy prices. Solar panels, especially with a battery, reduce energy dependence and allow savings on electricity bills.

• Self-consumption: You consume the electricity you produce, thus reducing your purchases from your energy supplier.
• Resale of surplus: If your production exceeds your consumption, you can resell the surplus electricity to your supplier, thus generating additional income.
• Tax credit and financial aid: Many aids are available to reduce the initial cost of the installation.

Investing in solar panels is an effective way to control your energy expenses and protect yourself against electricity price increases.

Valuation of the electricity produced

Beyond simply reducing your bill, the electricity produced by your solar panels can be a source of income. The mechanism of reselling the surplus allows to inject the electricity not consumed into the grid, and to be paid for it. This valuation of the electricity produced helps to accelerate the return on investment of your installation. A 6 kWp photovoltaic installation can save more than €34,800, or approximately 46% on electricity bills, over 25 years. A photovoltaic installation can generate additional income through the resale of surplus electricity.

Impact on the carbon footprint of the household

Opting for solar energy means making a responsible choice in favour of the environment. Solar panels produce clean and renewable energy, thus reducing your carbon footprint. By reducing your consumption of fossil fuels, you contribute to the fight against climate change and the preservation of the environment for future generations. Installing solar panels is a very interesting investment, offering a rate of return of 8 to 12% and significant savings. The installation of solar panels is an ecological investment that reduces the carbon footprint of the household.

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Conclusion: Choosing the right power for your solar panels

Ultimately, choosing the power of your solar panels isn’t just about numbers. It’s mainly about finding the right balance between what you really need and what’s possible at your place. Whether you’re aiming for pure self-consumption or want to sell your surplus, each project is unique. Think carefully about your energy consumption, the space you have on your roof, and your budget. Don’t hesitate to ask for the advice of professionals to have an installation that perfectly matches your situation. It’s the best way to fully enjoy solar energy and save money in the long term.

Frequently Asked Questions

What is the peak power of a solar panel?

The peak power (Wp or kWp) of a solar panel represents its maximum electrical production capacity in ideal conditions. It is essential to estimate the amount of electricity that your installation will be able to generate.

How to estimate the power of solar panels I need?

To determine the necessary power, it is first necessary to assess your annual electricity consumption, the size of your household, the area of your home, and your habits of using electrical appliances. An accurate analysis of these elements allows to adapt the installation to your real needs.

What are the important criteria for choosing the power of my solar installation?

Several factors influence the choice of power: your budget, the space available on your roof, and your main objective (self-consumption, resale of surplus or all of the electricity produced).

How many solar panels are needed for a house of 100 m²?

For a house of 100 m² without specific energy-intensive equipment, it is generally estimated a power of approximately 3 kWp, which corresponds roughly to 8 solar panels of 400 Wp each. However, a personalised simulation is always recommended.

How can I improve the performance of my solar panels?

To optimise the performance, it is crucial to consider the orientation and inclination of your roof, the impact of the ambient temperature, and to manage potential shaded areas (trees, neighbouring buildings).

Does the power of solar panels decrease over time?

Yes, it is important to know that solar panels undergo a slight loss of power over time (approximately 0.5% per year). The quality of the material and the guarantees offered by the manufacturer are therefore