Module 9: Energy Sharing and Surplus Allocation

Virtual energy sharing allows multiple consumers -- without needing to be physically connected to the same circuit -- to share the generation output of a common renewable asset, typically a community solar PV plant. Unlike individual distributed generation, this model decouples the physical location of the consumption point from the location of the generator, as long as both are within the same voltage level and service area of the network operator.

This is especially relevant for rural Colombian energy cooperatives, where the rooftops available for solar panels do not always coincide with the properties of the members interested in participating.

The mechanism works through "virtual energy accounts": the plant generates a total number of kWh in a billing period, and that total is distributed on an accounting basis -- not physically -- among the accounts of participating members, according to previously agreed allocation rules. The physical energy follows the laws of physics (it flows through the grid to the nearest consumption point), but the financial and regulatory accounting reflects the agreed allocation.

For boards of directors, understanding this distinction is crucial when explaining the model to new members: nobody receives "their" specific electron, but rather a contractual and accounting right to a portion of total generation, which translates into a credit or discount on their electricity bill.

CREG Resolution 101 072 of 2024 established the framework for distributed generation and large-scale self-consumption in Colombia, including two compensation mechanisms that cooperatives must distinguish precisely:

• Net metering -- surplus energy fed into the grid is compensated at the same tariff as energy consumed.
• Net billing -- surplus energy is remunerated at a different (generally lower) rate, tied to the avoided generation cost of the retailer.

The choice between these two schemes depends on the project size, the type of retailer, and the installed capacity thresholds defined by CREG for each category of self-generator.

For community energy cooperatives, the resolution also introduces the concept of "associated user" or collective distributed generation, which allows multiple meters at different premises to be accounting-linked to a single generation plant.

It is essential that cooperative leaders understand that this regulatory framework is still being developed in several operational aspects -- for example, the exact procedures for monthly reconciliation between the network operator and the community entity -- so it is advisable to maintain ongoing contact with the regional CREG office and the local network operator to verify current procedures before signing connection contracts.

A practical point: the cooperative must designate a single legal entity (the cooperative itself) as the holder of the connection contract with the network operator, and this entity is responsible for receiving the aggregated surplus settlement and redistributing it internally to its members according to the allocation rules approved by the general assembly in its bylaws.

There are three main families of allocation algorithms, each with different implications for equity and administrative complexity.

The pro-rata (proportional to capital contribution) model allocates generated energy in direct proportion to the investment or capital shares each member contributed to the project. It is the simplest model to administer and the easiest to explain in an assembly, but it can generate tension if a member with a high investment has low consumption (receiving credits they cannot use) while another with a low investment and high consumption comes up short.

The proportional to historical consumption model allocates energy according to each member's consumption pattern over a reference period (for example, the average of the 12 months before the plant began operating). This model maximizes the practical usefulness of credits for each household, but requires periodic updating and can penalize members who reduce their consumption through energy efficiency, creating a perverse incentive.

The Shapley value, drawn from cooperative game theory, calculates the average marginal contribution of each member to total generation considering all possible combinations of participation. In simple terms: rather than looking only at "how much you invested" or "how much you consume," the Shapley value asks "how much value does your participation add to the group, on average, if we imagine you joining and leaving different combinations of members." It is mathematically the most equitable model when there are large differences in consumption profiles, but its disadvantage is the complexity of calculation and explanation; in practice, mature cooperatives tend to use simplified approximations calculated by software.

A technically correct allocation that is poorly communicated generates distrust and avoidable conflicts. It is recommended that each cooperative deliver a monthly individual report of no more than one page to its members, including:

1. The total energy generated by the community plant that month.
2. The percentage and kWh specifically allocated to that member.
3. The resulting savings in COP compared to the retailer's standard tariff.
4. A simple comparison with the previous month.

This report should be delivered in non-technical language, avoiding jargon such as "Shapley value" or "pro-rata allocation" in the direct communication to the member; these terms are for internal use by the board of directors and the technical committee.

Every allocation model will sooner or later produce a dissatisfied member. It is recommended that the cooperative's bylaws include a three-person committee (rotating, elected by the assembly) dedicated exclusively to receiving and resolving allocation complaints within a maximum period of 15 business days, using a two-step procedure:

1. Technical verification of the metering data.
2. If the data are correct but the complaint is about the allocation rule itself, the committee escalates the case to the general assembly for a potential review of the model -- not to resolve the individual case retroactively.