Choosing the right solar kit for self-consumption

The growing desire for energy independence, coupled with the constant development of electric heating appliances such as heat pumps, has led to increased interest in solar photovoltaics. In particular, the self-consumption solar kit is gaining in both relevance and popularity. Let's take a look at what you need to know to make the right choice.

What is solar self-consumption?

Self-consumption means producing your own electricity and consuming it with your own electrical appliances. It is not necessarily total, meaning that you can be a self-consumer even if you only produce and consume 30% of your own electricity.

In addition, theself-consumption can be individual or collective. In the former case, for example, you have photovoltaic solar panels on the roof of your own detached villa, which you generate and consume from. In the second case, you consume electricity from one or more local producers of renewable photovoltaic electricity.

Self-consumption doesn't necessarily mean complete independence from the grid, since you can only consume your own electricity if you need it immediately when it's available, i.e. when solar energy is available.

Achieving a degree of independence would require the installation of storage systems that are still fairly expensive.

Choosing the right wattage for your solar self-consumption kit

To determine the right power for your self-consumption solar kit, you first need to work out how much electricity you need to cover. To do this, you need to make a list of all the appliances that consume electricity, and estimate how much time they run per day.

You will then obtain a certain amount of KWh or Killowatt hour that the production of the solar panels will have to cover.

If the theoretical maximum power of a solar panel, also known as peak power, is, for example, 300Wp = 300 Watt peak, then the solar panel will be able to deliver 300W at maximum capacity and under ideal theoretical conditions. In reality, it delivers 70% of this power, i.e. around 210-220W for a 300W panel.

This means that if you determine a total requirement of 20 kWh per day, considering 8 optimistic hours of production per day, we get 20,000 / 8 = 2500W per day to produce. At 210W per panel, we need 2500 / 210 = 12 panels of 300Wp. This is a rough estimate to give an idea.

Generally speaking, a self-consumption kit for a villa is around 3kWp of power supplied. Beyond that, the electricity is intended for resale.

What to take into account for the dimensioning?

To make the right choice, we need to take into account the profile of the home when the panels are able to produce, i.e. during the day and more often in summer.

In fact, it's irrelevant to consider electric heating, which operates in winter and at times when there's no sun.

On the other hand, all the basic consumption of the house that runs continuously, such as pump motors, ventilators, some appliance standby, etc., can generally cover these basic needs.

As the consumption of a washing machine is generally so high, it's not really relevant to include it in the calculation either, as the photovoltaic field would have to be oversized to compensate for this peak consumption. It's more reasonable to consider the average consumption to be compensated for, and to assume that peak consumption will still be covered by the usual grid.

The aim is to avoid inflating the initial investment and to maintain a return on investment within a few years, rather than over several decades, which would no longer make sense.

What kind of government aid is available for self-consumption in France?

The purchase and installation of a self-consumption kit requires a certain budget, which must be taken into account when calculating the return on investment. But there are also government subsidies available to help reduce the investment cost.

Solar installations that enable self-consumption are eligible for a premium based on their total peak power. This premium is often paid over a period of 5 years, by EDF, along with the income generated by the resale of your surplus (what is not self-consumed but still produced by the panels of your kit).

  • For a power lower than 3kWp: 380€ per kWp
  • For a power between 3 and 9kWp : 280€ per kWp
  • For a power between 9 and 36kWp: 160€ per kWp
  • For a power between 36 and 100kWp: 80€ per kWp

In addition, if they are connected to the grid and have a capacity of 3kWp or less, these installations can benefit from the reduced VAT rate of 10% instead of 20%.

How to install a self-consumption kit?

There are two options: stand-alone installation. If you're technically proficient and feel you can think your way around photovoltaic technology to ensure that your installation is well thought-out and works properly. Then install your panels yourself - you're never better served than by yourself.

However, if the orientation of the panels, the wattage to choose, the wiring, or even the use of a string inverter or microinverters seems like a complex challenge, then you may be better off opting for a team of seasoned pros who have already done the same at your neighbors' or friends' homes.

In most cases, they can even take care of the paperwork for government grants.

About the author

Reda holds a PhD in finance and specializes in renewable energy economics. He combines financial expertise with an interest in sustainability, writing not only on the financing of green projects, but also on more general topics and frequently asked questions in this field.