Distribution of photovoltaics in the site's consumption

Nicolas Vodoz Updated by Nicolas Vodoz

How is photovoltaic electricity distributed among consumers?

  1. Electricity consumption is divided into two parts: that coming from the grid and that from the photovoltaic (PV) system.
  2. To determine these two shares, Climkit defaults to the introduction meter, which includes two flows: withdrawal and feed-in to/from the grid, as well as consumption meters.
  3. The share of photovoltaics in consumption is calculated as follows: PV share = total consumption - withdrawal. 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 part not covered by the PV is then supplied by the grid.
  5. By relying on the flows from the introduction meter, it ensures that the withdrawal and feed-in are accounted for according to the billing and reimbursements of the DSO, and that the withdrawal is fairly distributed among consumers.
  6. Thus, photovoltaic production is derived using the following formula: Production = total consumption - withdrawal + feed-in. The site’s self-consumption rate is obtained by the formula: PV share / production.

Why is there feed-in and withdrawal from the grid within the same 15-minute period when production equals consumption?

  1. If at the beginning of the period, consumption exceeds production, withdrawal from the grid occurs. But if, at the end of the period, consumption decreases, the surplus production is fed back.
  2. If we did not rely on the introduction meter, we would have 100% site autonomy during those 15 minutes. However, this would not reflect the reality accounted for by the DSO, which bills withdrawal at the beginning of the period and compensates the feed-in at the end of the period.

Why is there some production at night?

  1. Given that there are losses and counting discrepancies (for example, the introduction meter often measures a withdrawal lower than that of all consumption meters, even without production), these discrepancies are absorbed in the calculation of the deducted production.
  2. If the withdrawal exceeds consumption, production at night is observed. This indicates that the introduction meter is less accurate than all the consumption meters combined.
  3. Conversely, if the withdrawal is lower 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 the withdrawal and therefore the share of the grid in consumption.

What to do in case of significant discrepancies between withdrawal and consumption?

  1. If the difference between withdrawal without production and consumption is significant, it indicates that at least one consumption point is unmeasured, meaning at least one meter is missing.
  2. Pending the installation of an additional consumption meter, a virtual meter can be created to deduct this "unmeasured" consumption. This virtual meter can then be added to the common area meter of the site or directly assigned to a billing point.
  3. By deducting this unmeasured flow, the introduction meter, consumption meters, and production meter are accounted for.

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

  1. This virtual meter would absorb all small differences and thus sometimes account for positive values and sometimes negative ones, influencing the share of the grid in consumer consumption, which would no longer exactly correspond to the amount billed by the DSO.
  2. Furthermore, if the virtual meter is assigned to the billing point of the common area, it would increase or decrease the consumption of the common areas, which would no longer correspond to what is actually measured by the common area meter.
  3. In conclusion, even though this would make the graphs more homogeneous (without nighttime production), the unmeasured flow should only be deducted if it truly corresponds to an unmeasured consumer. In all other cases, we deduct the production flow, which absorbs the discrepancies and losses, while remaining aligned with the introduction meter as accounted for by the DSO.

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