The allocation key decides how a building's total costs are split across its apartments – making it the single most common source of billing errors in Germany.
"Unless the parties have agreed otherwise, operating costs are to be allocated according to the share of living space. Operating costs that depend on recorded consumption or recorded causation by the tenants are to be allocated according to a standard that reflects the differing consumption or causation."
— § 556a (1) BGB (translated)
The four common keys
- Living area – the statutory default; fair for area-driven costs like insurance or property tax.
- Headcount – sensible for unmetered waste and water; error-prone in practice (who actually lives there?).
- Per unit – equal share per apartment; fits elevator servicing or cable.
- Consumption – mandatory wherever metering exists (water meters, heating under the HeizkostenV).
Condo associations differ
Between owners, § 16 (2) WEG allocates by co-ownership shares unless resolved otherwise. Letting owners therefore often "translate": the Hausgeld statement by ownership share is not identical to the tenant statement by living area.
Changing the key
Landlords may switch unilaterally only within narrow limits (§ 556a (2) BGB: moving to consumption billing). Anything else needs a contract amendment – and in a WEG, a resolution. Consistency is mandatory: once chosen, the key applies for the whole period.