Short Definition
Self-consumption optimization refers to the targeted use of locally generated PV electricity at the site where it is produced. As much of the generated energy as possible is consumed directly, temporarily stored in a battery energy storage system (BESS), or used by flexible loads instead of being fed into the electricity grid. This can avoid subsequent grid consumption and improve the economic viability of the system.
Self-Consumption Optimization at a Glance
- PV electricity primarily supplies the loads currently operating at the site.
- Surplus PV energy can be stored in a BESS and used when demand arises later.
- Flexible loads can be shifted to periods of high PV generation or activated selectively.
- Other operating objectives may take priority over maximizing the self-consumption ratio.
How Does Self-Consumption Optimization Work?
Self-consumption optimization is based on the continuous balancing of energy flows. For this purpose, an EMS records PV power, site consumption, the state of charge and power of the BESS, as well as grid import and export at the grid connection point. In simplified terms, the current energy surplus is calculated as the difference between PV generation and site consumption.
If PV generation exceeds current consumption, the EMS can charge the BESS or activate flexible loads. Surplus energy that cannot be used at the site is generally fed into the electricity grid. PV power is curtailed only if required by technical, regulatory, or economic constraints, such as an export limitation or a corresponding energy-market signal.
If consumption exceeds the current PV power, the BESS can be discharged to reduce grid import. The control system considers factors such as permitted states of charge, charging and discharging power limits, conversion losses, available storage capacity, and reserved energy. For flexible loads, operating permissions, minimum runtimes, power limits, and time windows must also be considered.
Self-consumption optimization can be combined with peak shaving, export limitation, dynamic electricity tariffs, or external flexibility marketing. The EMS must coordinate the different requirements according to defined priorities and operating limits.
Two key performance indicators are primarily used for evaluation:
- Self-consumption ratio = PV energy used on site / total PV generation
- Self-sufficiency ratio = consumption covered by the site’s own PV energy / total site consumption
The self-consumption ratio therefore indicates the proportion of generated PV energy that is used at the site. The self-sufficiency ratio, by contrast, describes the proportion of total electricity consumption covered by the site’s own PV generation. A high self-consumption ratio does not necessarily result in a high self-sufficiency ratio.
If the BESS can also be charged from the electricity grid, the origin of the stored energy must be considered in the evaluation. Only energy used directly from the PV system or previously stored from the site’s own PV generation counts as self-supplied energy. Grid energy discharged at a later time must not be fully attributed to PV self-consumption or the self-sufficiency ratio. Depending on the metering and energy-accounting concept, storage and conversion losses may also be treated differently.
Where Is Self-Consumption Optimization Used?
- Commercial and industrial facilities: PV generation, production loads, and the BESS are coordinated to reduce grid import during operation.
- Sites with charging infrastructure: Charging processes can be shifted to periods with a PV surplus or adjusted in terms of charging power within operational limits.
- Systems with a BESS: Surplus PV energy is shifted over time and made available for subsequent consumption at the site.
- Hybrid energy systems: The EMS coordinates PV, BESS, controllable loads, and additional generation sources while taking multiple operating objectives into account.
Benefits, Limitations, and Technical Requirements
Self-consumption optimization can reduce energy costs when electricity imported from the grid is more expensive than the economic value of exported energy. It can also reduce both grid import and grid export while aligning available generation and storage capacity more effectively with the site’s load profile.
The achievable result largely depends on the timing of PV generation relative to consumption. Other influencing factors include the sizing of the PV system, usable storage capacity, BESS power and efficiency, available flexible loads, and the applicable electricity import and export conditions. An oversized BESS may achieve only a small number of additional charging cycles and is therefore not automatically economically viable.
Maximizing the self-consumption ratio is not necessarily the most economically beneficial objective. If the BESS is also used for peak shaving, dynamic tariffs, or external flexibility marketing, reserving storage capacity for these applications may provide greater value. Reliable measurements, controllable components, suitable communication interfaces, and clearly defined priorities and operating limits are therefore required.
How Does EcoPhi Implement Self-Consumption Optimization?
EcoPhi can consolidate measurement data from PV systems, BESS, loads, and the grid connection point. Based on these data, the EMS determines the current energy surplus or deficit and transmits suitable charging, discharging, or power setpoints to the controllable components. Flexible loads can be controlled depending on the PV surplus, state of charge, time windows, and other operating conditions.
Additional requirements such as peak shaving, export limitation, or reserved storage capacities can be incorporated into the prioritization logic on a project-specific basis. Dashboards and historical analyses can display self-consumption, the self-sufficiency ratio, grid import, and grid export. If the BESS can be charged from the grid, the applied metering and energy-accounting concept must appropriately account for the origin of the stored energy.
The specific implementation depends on the available device interfaces, control capabilities, and project requirements. Additional integration or engineering services may be required.
Brief Summary
Self-consumption optimization coordinates local PV generation, consumption, BESS, and flexible loads. It can reduce grid import and energy costs. The key requirements are a suitable load and system profile, reliable measurement data, and a control strategy that considers technical limits and additional operating objectives.
Frequently Asked Questions About Self-Consumption Optimization
What Is the Difference Between the Self-Consumption Ratio and the Self-Sufficiency Ratio?
The self-consumption ratio describes the proportion of total PV generation that is used at the site. The self-sufficiency ratio describes the proportion of site consumption covered by the site’s own PV energy.
How Does a BESS Increase Self-Consumption?
A BESS stores surplus PV energy and makes it available for local consumption at a later time. The actual benefit depends on factors including storage capacity, power, efficiency, and the load profile.
Is a Self-Consumption Ratio of 100 Percent Always Beneficial?
No. Achieving a very high ratio may require unfavorable system sizing or less economically efficient use of the BESS. Other applications, such as peak shaving or dynamic tariffs, may provide greater economic benefits.
What Data Does an EMS Require for Self-Consumption Optimization?
The EMS primarily requires current values for PV generation, site consumption, power at the grid connection point, and the power and state of charge of the BESS. For flexible loads, operating permissions, power limits, and time constraints are also relevant.
Does Energy Charged from the Electricity Grid Count as PV Self-Consumption?
No. If a BESS is charged from the grid, the grid energy discharged at a later time must not be counted as self-consumed PV energy. Its origin must be considered in the metering and energy-accounting concept.