Distribution of photovoltaics in the site's consumption

How is photovoltaic electricity distributed among consumers?

1. The consumption of electricity is divided into two parts: that from the grid and that from the photovoltaic installation (PV).
2. To determine these two shares, Climkit defaults to the introduction meter, which includes two flows: extraction and feedback to/from the grid, as well as consumption meters.
3. The share of photovoltaics in consumption is then calculated as follows: PV share = total consumption - extraction. The site's autonomy rate is obtained using the formula: PV share / total consumption.
4. Climkit distributes the PV share among consumers every 15 minutes by applying the site's autonomy rate to their individual consumption. The portion not covered by PV is then supplied by the grid.
5. By relying on the flows from the introduction meter, it ensures that extraction and feedback are accounted for according to the billing and compensation by the DSO, and that extraction is distributed fairly among consumers.
6. The photovoltaic production is then deduced using the following formula: Production = total consumption - extraction + feedback. The site's self-consumption rate is obtained by the formula: PV share / production.

Why is there feedback and extraction from the grid in the same 15-minute period while production equals consumption?

1. If at the beginning of the period the consumption exceeds production, one extracts from the grid. However, if by the end of the period, consumption decreases, the excess production is fed back.
2. If one did not rely on the introduction meter, there would be 100% site autonomy during those 15 minutes. However, this would not reflect the reality accounted for by the DSO, which bills extraction at the beginning of the period and compensates for feedback at the end of the period.

Why is there a bit of production at night?

1. Given that there are losses and counting discrepancies (for example, the introduction meter often measures an extraction lower than that of all consumption meters, even without production), these discrepancies are absorbed in the calculation of the deducted production.
2. If the extraction exceeds consumption, some production is observed at night. This means the introduction meter is less precise than the total of the consumption meters.
3. Conversely, if extraction is less than consumption, negative production results, indicating that part of the consumption is not measured by a meter.
4. If these values remain minimal, they represent normal losses in the installation that can be ignored, as they slightly reduce production without affecting extraction and thus the share from the grid in consumption.

What to do in case of large discrepancies between extraction and consumption?

1. If the difference between extraction without production and consumption is significant, it indicates that at least one consumption point is not measured, meaning at least one meter is missing.
2. While waiting for the installation of an additional consumption meter, a rule meter can be created to deduct this "unmeasured" consumption. This rule meter can then be added to the site's common meter or directly assigned to a billing point.
3. By deducting this unmeasured flow, consideration is given to the introduction meter, consumption meters, and production meter.

Why not create a rule meter and deduct the unmeasured flow in all cases?

1. This rule meter would absorb all small differences and would sometimes account for positive values and sometimes negative, influencing the share from the grid in consumers' consumption, and it would no longer exactly correspond to the amount billed by the DSO.
2. Moreover, if the rule meter is assigned to the common billing point, this would increase or decrease the consumption of the commons, which would no longer correspond to what is actually measured by the commons meter.
3. In conclusion, even if this would make the graphs more consistent (without nocturnal production), the unmeasured flow should only be deducted if it is indeed an unmeasured consumer. In all other cases, the production flow is deducted, which absorbs discrepancies and losses while remaining aligned with the introduction meter as accounted for by the DSO.

How does a battery work and what is its impact on self-consumption?

1. The installation of a battery allows the storage of excess photovoltaic (PV) electricity produced on a site. When photovoltaic production exceeds instantaneous consumption, the surplus is stored in the battery.
2. Once the battery is fully charged, any additional surplus is injected into the electricity grid.
3. When consumption exceeds solar production, the battery discharges to supply consumers in the building. This mechanism significantly increases the self-consumption rate, as solar electricity produced during the day is also available at night.
4. When the battery is empty, any additional electricity is automatically extracted from the grid.

Why are there differences between the photovoltaic inverter data, the DSO, and the Climkit platform?

It is completely normal to observe discrepancies between the data displayed on the Climkit platform, those measured by the inverter, the battery, or the network operator's (DSO) meter.

Several reasons explain these differences:

1. Meter tolerance: Certified meters (e.g., MID) have an accuracy between 0.5 and 1%. Other meters, such as some "smart meters" integrated into the inverter, may be slightly less accurate.
2. Type of counting: Direct counting (meter plugged directly into the circuit) is more accurate than indirect counting with current transformers (CT). For better results, matching CTs should be used based on the actual intensity measured. In practice, DSOs often install oversized CTs, which can lead to underestimation at low intensity.
3. Calculation methods: Self-consumption of electricity on a photovoltaic site is generally calculated from different measurements and not directly recorded. Systems may deduce certain values from others, which introduces differences: for example, an inverter may estimate the building's consumption based on production and the introduction measurement (extraction and feedback), while another system may calculate production based on measured consumptions.
4. Measurement location and losses: The production indicated by the inverter corresponds to the electricity generated in direct current (DC), while Climkit measures that which is actually injected in alternating current (AC) into the building's grid, after conversion. The DC/AC transformation and the cables incur a loss of 3 to 5%.
   In case of using a MT/BT transformer (low/high voltage), the losses are about 5%.
5. Measurement frequency: Systems measure and transmit data at different intervals (every minute, every 5 or 15 minutes, at fixed or random times, etc.), which can generate small differences, especially if consumption varies rapidly. Additionally, rounding of numbers can lead to slight discrepancies in the total over a period.
6. Presence of a battery: If the site includes a battery, the method of counting the energy stored or returned varies according to the systems, particularly at night when the battery discharges. Small amounts of energy may be injected or extracted from the grid without always being accounted for by the battery monitoring system.

In summary, differences of a few percent (or a few kWh) between two counting systems are normal and do not mean that there is an error or malfunction.

How to verify the accuracy of the measurements?

Climkit regularly checks the consistency of its measurements. The simplest test is to examine the data at night: without solar production, the sum of individual consumptions should correspond to the energy imported from the grid (main meter). This "night test" is a good indicator of the system's operation.

For another system, it is advisable to consult the installer to verify the configuration and correct functioning of the hardware.

Finally, to compare two systems accurately, it is recommended to export and compare load curves (in 15-minute intervals) over several days. These data, available on the Climkit platform (Excel file), allow for a detailed analysis of any differences.