How many solar panels for a 100m² house?
Solar panels are an increasingly popular solution to reduce household electricity consumption and promote self-consumption. For a 100m² house, it is crucial to determine how many solar modules are needed to cover energy needs. This article explains how to calculate consumption, estimate the power required, assess the available roof area, estimate the energy production of solar panels, and finally, determine the cost of installation.
Calculate consumption and power required
Estimate the electricity consumption of the house
The first step is to estimate the home's electricity consumption . In France, the average consumption of a household is around 4,679 kWh per year. However, for a 100m² house, this consumption can vary depending on several factors such as the number of occupants, the energy efficiency of the house, and consumption habits. A more accurate estimate can be obtained by consulting electricity bills over a full year.
Determine the power of solar panels required
Calculate the power in kWc required
To determine the power of the solar panels required, it is first necessary to convert the annual consumption in kWh into power in kilowatt-peak. On average, a solar panel produces about 1,000 kWh per kWp installed per year under ideal sunlight conditions.
For a house consuming 4,679 kWh per year:
Power in kWc required = Annual consumption in kWh / (1000 kWh/kWc) = 4679 / (1000 kWh/kWc) = 4.679
Convert power in kWc to number of panels
The solar panels available on the market have varying powers, generally between 300 Wp and 450 Wp. To simplify the calculation, let's take an average power of 400 Wp per panel.
To determine the number of panels needed:
Number of panels = Power in kWc required / Power per panel in kWc = 4.679 kWc / (0.4 kWc/panel) ≈ 12 panels
Consider the area available for installation
Evaluate the available roof area
Assessing the available roof area is a crucial step. On average, a solar panel measures approximately 1.6 m² .
To install 12 panels, you therefore need: Surface area required = 12 panels × 1.6 m²/panel = 19.2 m²
The available roof area should be free of obstructions (such as chimneys or dormers) and ideally facing south with a 30-40 degree slope to maximize efficiency.
Calculate the number of panels that can be installed on this surface
If the available roof area is greater than 19.2 m², it is possible to install the necessary 12 panels. Otherwise, the number of panels will have to be adjusted according to the surface area actually available.
Estimate the energy production of solar panels
Calculate energy production in kWh
The energy production of a solar panel depends on several factors, including sunlight, orientation, and inclination of the panels. In France, a 1 kWc solar panel produces on average between 900 and 1,400 kWh per year.
For 4,679 kWc installed:
Estimated annual production = 4.679 × (1200 kWh/kWc) = 5614.8 kWh
Average annual production in kWh is a key indicator for assessing the efficiency and profitability of solar panels , allowing users to predict savings on their electricity bills and calculate the return on investment of their solar installation.
Analyze the coverage of the home's energy needs
If the house consumes 4,679 kWh per year and the installation produces 5,614.8 kWh per year, there is a surplus of energy, which can be stored or sold back to the electricity grid. This means that the solar installation can cover and even exceed the energy needs of the house.
Estimate your energy needs
To estimate your energy needs, you can refer to the electricity consumption standards by type of item.
We therefore consider that the electricity consumption is approximately:
- 110 kWh/m²/year for heating,
- 1,100 kWh/household/year for electrical appliances,
- 800 kWh/person/year for domestic hot water,
- 200 kWh/person/year for cooking.
Depending on your estimated annual energy consumption, you will be able to determine the power of the photovoltaic system. However, be aware that you do not size your photovoltaic installation to match your electrical needs exactly since part of a household's energy consumption occurs when the sun is not shining.
It is considered that the power of the photovoltaic installation must cover approximately a third of its needs.
Determine the cost of installation
Evaluate the price of solar panels and installation
The cost of solar panels and installation varies depending on the quality of the panels, the complexity of the installation and the installation costs. On average, the cost of a solar kit is approximately €1,000 to €1,500 per kWp installed , including photovoltaic panels, inverter, cables, etc. excluding installation costs.
For a 4.679 kWc installation: Estimated cost = 4.679 × 1500 €/kWc = 7018.5€
Your consumption profile will determine the number of solar panels to install.
For a house of about 100 m² using only electricity and standard equipment (such as a washing machine, dishwasher, dryer, oven, television, etc.), you will need about 4 kWp of solar panels . This corresponds to about 20 m² of roof and 10 solar panels , although this number can vary depending on the nominal power of the photovoltaic panels chosen.
The efficiency of solar panels
Solar panel efficiency , expressed as a percentage, indicates the ability of the panels to convert sunlight into usable electricity . This efficiency varies depending on the technology used, with monocrystalline panels often being the most efficient, with conversion rates ranging from 18 to 22%.
Use of solar energy
The number of solar panels you install will also depend on the type of installation you choose. There are three options:
- Partial self-consumption with resale of surplus.
- The total sale of electricity to an energy supplier.
- Total self-consumption.
Today, installing solar panels for self-consumption with resale of surplus is the most advantageous for a main residence. This solution allows:
- Consume your own production throughout the lifetime of the solar panels (on average 20 years).
- Inject and sell the surplus produced on the network at a guaranteed price.
- Save money by not depending entirely on your energy supplier for part of your electricity needs.
If your roof surface allows it, it may be wise to install a larger production capacity . To further improve the profitability of your investment, you can try to increase your photovoltaic self-consumption rate using solutions such as supervision systems allowing load control.
