Gemeinschaftliche Gebäudeversorgung (GGV)

The contract, and what it leaves out

The instrument is the Gebäudestromliefervertrag, signed between the system operator and each participating household or business. It covers the solar power generated on the building and nothing else. Residual power stays with each participant's own retailer, and that is precisely where the regulatory relief comes from: an operator who does not supply in full does not carry the duties of a licensed supplier.

The statute sets two boundaries itself. Participation is voluntary and may not be tied to the lease, and the contract may not run longer than two years. Price, by contrast, is freely negotiated: the 90% cap belongs to Mieterstrom and does not apply here.

The allocation key decides the volume

Generated power is allocated to participants per quarter hour, following a key agreed in the contract. A static key works from fixed shares per unit, by floor area for instance. A participant who does not consume their share within that quarter hour hands it to the grid, while another participant is drawing grid power at the same moment.

A dynamic key allocates by actual consumption in the same quarter hour instead. In a worked four-kilowatt-hour interval across three units, the share of output used inside the building rises from roughly 62% to roughly 88%. No method is prescribed in law; the design sits with the operator and its billing.

What the metering demands

Every quantity, generated and consumed, has to be measured in quarter-hour intervals. That means intelligent metering systems with a smart meter gateway for generation and for every participant, a metering point operator supplying those readings, and billing that turns them into monthly allocations. The residual supplier then also bills on measured values rather than a standard load profile.

Observed in project review: against a system that only exports, the uplift runs around 20 EUR per kWp once and roughly 3 EUR per kWp per year thereafter. On 100 kWp that is about 2,000 EUR of capital cost and 300 EUR a year, carried by metering, data handling and billing.

GGV is an operating decision rather than a consenting question. The effort does not land during construction; it lands afterwards, every month, for twenty years: computing allocations, billing participants, handling arrivals and departures. Where nobody owns that task, the model books revenue nobody collects.

For valuation this means the volume used inside the building is a band, not a number. It follows the key, the participation rate and the load profiles of the units, and all three move. A two-year contract term is shorter than any financing built on top of it.

In a lender's pack, then, what carries is not the name of the model but the chain of evidence beneath it: signed Gebäudestromlieferverträge, a named metering point operator committed to delivering quarter-hour values, and the agreed key. Without that chain the project is re-run on the export case, and the gap between the two calculations is the real finding.