The degree of self-sufficiency (or autarky rate) is a percentage that describes the level of independence a household or business has from the public power grid. In short, it refers to the proportion of total electricity consumption that is covered directly by one's own photovoltaic system (and, if applicable, a battery storage system).
In a nutshell: A self-sufficiency degree of 70% means that you generate nearly three-quarters of your annual electricity needs completely by yourself. Only the remaining 30% needs to be purchased from your energy supplier. The higher this value, the more shielded you remain from rising electricity prices.
Difference Between Self-Sufficiency Degree and Self-Consumption Rate
These two terms are frequently confused in practice, yet they describe two completely different perspectives of solar system economics. While the degree of self-sufficiency measures what percentage of your consumption comes from your own production, the self-consumption rate indicates what percentage of the generated solar power you use yourself within the building and how much is fed into the grid.
For example, a small PV system can achieve a self-consumption rate of nearly 100% because every generated watt is consumed immediately. Nevertheless, the degree of self-sufficiency remains low because the small system does not provide enough overall energy to cover a significant portion of the total demand.
Advantages and Features at a Glance
Targeted optimization of your degree of self-sufficiency brings tangible economic benefits:
- Cost Control: Every kilowatt-hour you generate and consume yourself protects you from grid fees, taxes, and price fluctuations in the electricity market.
- Maximum Benefit Through Battery Storage: Without a battery storage system, the self-sufficiency rate of pure PV systems usually sits at only 30% to 40%, since the sun does not shine in the evening and at night. Integrating a modern battery storage system can easily increase this value to 70% or 80%.
- Sustainability: A high degree of self-sufficiency stands for the active use of locally produced green electricity and drastically reduces your household's ecological footprint.
What Should You Consider When Planning a System?
Complete 100% self-sufficiency throughout the entire year is usually not economically sensible in Central Europe. To bridge the dark winter months completely independently, the PV surface area and the battery storage would have to be extremely oversized, which drives up acquisition costs disproportionately.
The sweet spot for single-family homes is typically a degree of self-sufficiency between 70% and 85%. You can achieve this optimum through smart sizing tailored to your real consumption, combining your solar modules with a modern lithium iron phosphate (LiFePO4) storage system.