Sizing a PV system: How to determine the optimum size for your system

The essentials in brief

- Rules of thumb provide an initial guide to the minimum size of your photovoltaic system before detailed planning is carried out by a specialist company such as SolarHub.

- The basic rule is: use the entire roof area to benefit economically in the long term.

- Monocrystalline solar modules require only 5-7 m² of surface area for 1 kWp.

- A 4-person household with an annual electricity consumption of around 4,000 kWh requires a solar system with an output of 10 kWp, which corresponds to around 50 m².

What factors influence the size of a PV system?

The aim of a photovoltaic system is to reduce your electricity costs, become more independent of the power grid and ensure a sustainable supply. The optimum size of your PV system depends on the following factors:

- Roof size: The available roof area determines the maximum number of solar modules.

- Building requirements: Check whether there are any requirements for listed buildings or whether planning permission is required.

- Electricity requirement: The system should cover at least 30 % of your own requirements. Take future increases in demand into account.

- Solar radiation: A south-facing orientation is ideal; an east or west-facing orientation also delivers over 80 % of the maximum yield.

- Roof pitch: The optimum pitch is 35 degrees.

- Efficiency of the modules: High-quality modules are more efficient.

- Budget: Your investment framework influences the planning.

Dimensioning of the solar system for at least 30 % self-consumption

The use of self-generated solar power is now more economical due to lower feed-in tariffs. Without storage, PV systems cover around 30 % of demand; with storage, self-consumption can be increased to around 70 %.

Is 100% self-sufficiency possible?

Complete independence from the electricity market is not yet economically viable. A realistic and economically viable goal is self-consumption of around 70 %.

SolarHub recommends: Use the entire roof surface for photovoltaics

Experts advise using the entire roof area, as larger systems are cheaper per kilowatt and generate more electricity. They are also prepared for future increases in electricity demand, such as the use of electric cars or heat pumps.

Rule of thumb: What is the minimum size of your PV system?

Calculate the available roof area based on the number and size of roof tiles. Take dormers, chimneys and skylights into account.

How to calculate your annual electricity consumption

The power consumption can be calculated using the following rule of thumb:

Living space in sqm x 9 kWh + number of people x 200 kWh + number of large electrical appliances x 200 kWh = electricity consumption in kWh per year

Calculation of the PV system output

For a family of 4 with an annual electricity requirement of 4,000 kWh:

4,000 x 2.5 / 1000 = 10 kWp

Number of solar modules

Around 50 m² of roof area is required for 10 kWp output. High-quality, monocrystalline solar modules with an efficiency of 20-22 % only require 5-7 m² per 1 kWp.

Conclusion: Individual dimensioning of photovoltaic systems

Adapt the PV system output and storage size to your future annual electricity consumption. Use the entire roof area and opt for high-efficiency modules. A well-planned system will pay for itself within a few years.