Photovoltaic system: how many KWp do I need? The best tips for understanding your energy needs


Emma Potter

Installing a photovoltaic system is an increasingly popular choice for those who want to reduce energy costs. However, one of the most common questions customers ask concerns the amount of KWp needed for their photovoltaic system.

Determining how many kilowatt peaks (KWp) you need is a crucial step in ensuring that your system is efficient and adequate for your energy needs. What are the factors to consider? How to calculate the energy needs of your home or business?

In the next lines, we will explore the process for determining the useful power of a home photovoltaic system and provide a practical guide to help you make informed decisions.

What is KWp?

The peak kilowatt (KWp) is the unit of measurement that indicates the maximum power that a photovoltaic system can produce in optimal conditions of solar radiation. This value is fundamental to understand the system's ability to generate electricity.

The KWp is determined in the laboratory, simulating ideal conditions such as a temperature of 25°C and solar irradiation of 1000 watts per square meter. Knowing the KWp of your system is essential to correctly size the system based on the energy needs of the building, thus guaranteeing optimal performance and maximum efficiency.

How to determine the power needed

To understand how many KWp you need for your home's photovoltaic system, you need to do a sort of energy check-up. It's a bit like taking measurements to make a dress: you have to consider every detail to get the perfect result. So, in addition to looking at how many appliances you have, you also need to take into account when and how you use them.

For example, you may use more energy during the day when you work from home, and less at night when the house is quiet and everyone is asleep. And don't forget that consumption may also vary with the seasons: in summer, you may turn on the air conditioning more, while in winter, you may make intensive use of the heating.

In short, you need to put all this information together to get the full picture of your energy needs.

How to analyze your energy needs

After having done an energy check-up on your home, it's time to understand how much you actually consume. This phase is fundamental because it allows you to have a clear overview of your needs and plan accordingly.

So, to calculate how much energy you need, you'll need to look at your past bills or use online tools specifically designed to estimate your energy consumption.

Once you have obtained the necessary data, you will be able to have a clearer vision of your average monthly impact and the seasonal trend of consumption. This will allow you to establish a solid basis for the sizing of your photovoltaic system, ensuring you have adequate power to cover your daily needs, at any time of the day and year.

Here are some examples of average consumption by family type:

  • Family of 1-2 people
    Annual consumption: 2,000 – 3,000 kWh
    Daily requirement: 5.5 – 8.3 kWh
  • Family of 3-4 people
    Annual consumption: 3,000 – 4,500 kWh
    Daily requirement: 8.3 – 12.5 kWh

How is the photovoltaic system sized?

This is the step where you turn the numbers into action, ensuring your system can provide the energy you need efficiently and reliably.

The sizing of the photovoltaic system involves calculating the power required in peak kilowatts (KWp). Fortunately, there are several formulas and methodologies available to perform this calculation precisely and accurately.

One of the key variables to consider is the average solar radiation in your area. In fact, the amount of sun you receive during the day will directly influence the amount of energy your photovoltaic system will be able to produce. So, if you live in an area with a lot of sunny days, you may need fewer solar panels to achieve the same output as someone who lives in a cloudier place.

In addition to this variable, it is also important to consider the efficiency of the solar panels themselves. As with any technology, there are differences in efficiency between different models and brands of solar panels. Making sure you choose high-quality devices with proven efficiency can make a difference in the overall performance of the system.

The best power optimization strategies

In addition to ensuring the correct sizing of the system, there are a series of strategies that can be adopted to maximize the use of the solar energy produced.

One of the most effective is the installation of energy storage systems, also known as solar batteries or storage systems. These devices allow the electricity produced by the panels to be stored during peak solar production hours, when the sun is highest in the sky and power generation is greatest.

In this way, rather than sending excess energy to the electricity grid, it is stored inside the batteries to be used at times when solar production is reduced or absent, such as at night or during cloudy days.

Other solutions include the use of advanced monitoring and control devices, such as home energy management systems (EMS), which allow you to monitor the flow of energy inside the home in real time and automatically adjust consumption and production based on the user's needs and environmental conditions. These intelligent systems can help optimize the self-consumption of solar energy, thus reducing dependence on the traditional electricity grid and increasing the economic return of the photovoltaic system.

Furthermore, there are also innovative technologies such as bifacial photovoltaic modules and solar tracking systems that allow panels to capture more energy from light, both direct and reflected, thus improving the overall efficiency of the system.

These advanced solutions can be particularly useful in contexts where space for installing solar panels is limited or in areas with variable climate conditions.

The role of professional consultancy

While it may seem tempting to tackle the project yourself, advice from an industry expert can make the difference between a well-sized, efficient solar system and one that fails to meet expectations.

A photovoltaic professional has in-depth knowledge of solar technologies, local regulations and best installation practices. This experience is crucial to evaluating a home's specific energy needs and proposing customized solutions that maximize energy efficiency and reduce long-term costs.

Furthermore, a specialized technician will also be able to guide you in choosing the optimization strategies we have seen above. These solutions can make the difference between a photovoltaic system that only partially works and one that offers excellent performance in all conditions.

Finally, a professional consultant can manage all the practical aspects of the installation, including planning, planning permission, the installation itself and commissioning, giving you peace of mind that the job is complete, done right.

Determining how many KWp you need for your photovoltaic system is a crucial step in the process of exploiting solar energy. With careful planning and professional advice, you can maximize the benefits while reducing your environmental impact and costs. Investing in understanding your energy needs can lead to rewarding long-term results for you and the environment.