In times of rising and fluctuating electricity prices, more and more operators of PV systems are trying to increase their self-sufficiency. This makes them more independent of the electricity supply and achieves price stability. Here we show you what self-sufficiency is and how to calculate the degree of self-sufficiency in PV.
What does self-sufficiency mean in photovoltaics?
In the context of a solar system, self-sufficiency refers to the degree of independence that a system operator has from the power grid. The more solar power you use, the more self-sufficient you are. If you use all of the solar power you generate yourself, this is called complete self-sufficiency. The degree of self-sufficiency determines how self-sufficient you are. This indicates the proportion of self-consumption to total electricity consumption.
How do I calculate the degree of self-sufficiency with PV?
To calculate the level of self-sufficiency with PV, divide your own consumption by your total consumption. To determine the self-consumption of a PV system, subtract the electricity fed into the grid from the electricity generated. The higher the level of self-sufficiency, the more electricity is generated in relation to the total demand.
The formula for calculating the degree of self-sufficiency is:
- Degree of self-sufficiency (%) = self-consumption (kWh) / total consumption (kWh) * 100
The average level of self-sufficiency of a PV system is 30%. If you increase your own consumption, for example by using a PV storage system, you also increase your level of self-sufficiency.
| Characteristic | PV system without storage | PV system with storage |
| self-consumption | 1,500 kWh | 3,500 kWh |
| total consumption | 5,000 kWh | 5,000 kWh |
| degree of self-sufficiency | 30% | 70% |
Alternatively, you can also determine your level of self-sufficiency with the Independence Calculator of the HTW Berlin easy to determine.
What is a good and realistic level of self-sufficiency?
A level of self-sufficiency of 70 to 80% is desirable due to the high electricity prices. The self-sufficiency of a PV system without storage is 30 to 40%. With a PV system with storage you can achieve a self-sufficiency of 70 to 80%.
Is 100% self-sufficiency possible?
An autarky of 100% is currently only with an island system possible. Island systems have no grid connection and are therefore solely dependent on solar power. However, large PV systems and PV storage are required to cover the electricity demand all year round. This approach is costly and not economically viable.
How can I increase the level of self-sufficiency?
There are several ways to increase the level of self-sufficiency.
increase self-consumption
The best way to increase the level of self-sufficiency is to use more of the self-generated solar power in the householdThis makes you more independent from electricity suppliers and reduces your electricity costs. At the same time, unlike electricity prices, you achieve price stability because the electricity production costs remain the same.
There are numerous ways to increase the level of self-sufficiency. The most popular option is to add a power storageYou can also increase your own consumption using a heat pump or electric car. Operators are increasingly using solar power to heat water. An energy management system is recommended for optimized own consumption.
Add energy management system
An energy management system monitors and optimizes energy consumption for maximum performance at minimum cost. It identifies and records potential energy savings. First, it records and analyzes energy flows and sources in the home. Then it develops and implements improved consumption profiles.
Technical planning and installation of the PV system
Proper planning and installation are essential for the efficient operation of a PV system. On the one hand, the individual components need to be correctly dimensioned, and on the other, all system components must be coordinated with one another. Then, it is important that the system is installed correctly. Otherwise, there is a risk of performance losses and reduced yields, which will damage the level of self-sufficiency.
What is the difference between self-sufficiency and self-consumption?
The degree of self-sufficiency indicates the proportion of self-consumption of total consumption. The self-consumption rate indicates the proportion of self-consumption compared to the amount of solar power generated. Normally, the level of self-sufficiency is higher than the self-consumption rate. The higher the self-consumption, the closer the level of self-sufficiency and the self-consumption rate are to each other.
Based on a example calculation we will show you the difference between the self-consumption rate and the degree of self-sufficiency. Let us assume the following:
- Annual electricity consumption: 5,000 kWh
- Annual PV yield: 6,000 kWh
- Annual self-consumption: 2,000 kWh
In this case, the degree of self-sufficiency is % and the self-consumption rate is %.
- Degree of self-sufficiency = Annual self-consumption / Annual electricity consumption * 100 = 2,000 kWh / 5,000 kWh = 40%
- Self-consumption rate = Annual self-consumption / Annual PV yield = 2,000 kWh / 6,000 kWh = 33%
