Splitting heating costs: fixed share and consumption share (30/70)

#Two shares: fixed and consumption

With central heating and heat cost allocators, the fuel cost is split in two parts (UNI 10200; D.Lgs. 102/2014 art. 9 c. 5):

• the fixed share, split on the heating table;
• the consumption share, split on the allocators' readings.

Running, the terzo responsabile and maintenance of the plant are not split this way: they go on the heating table.

#Where the percentage comes from

The fixed share is taken, in this order:

1. from the regolamento's article or the resolution that sets it (if the regolamento states only the consumption share, the fixed one is 100 minus it);
2. from what the person preparing the split states;
3. if nobody states it, 30 % by table and 70 % by consumption is applied, as D.Lgs. 102/2014 allows — but the split stays to verify: the share must be confirmed by a UNI 10200 technical report or a resolution.

So 30/70 is not a fixed rule: it is the value used when the percentage is written nowhere, and it must be confirmed.

#The calculation, step by step

1. Take the period's fuel amount (for a bill spanning two periods, only the period's days).
2. The fixed share is the percentage of the amount; the consumption share is the rest.
3. The fixed share is split on the heating table's millesimi; the consumption share on the allocators' readings. Both are rounded to the cent, with the remaining cents going to the largest remainders, so each share adds back to the cost.

A unit that consumed nothing — an empty flat — still pays its fixed share. In the recorded example (24 units on two staircases, 30/70 written in the regolamento) the €11,872.69 of gas goes €3,561.80 on the table and €8,310.89 on the allocators.

#Readings: what to check

Readings usually come from the reading company as CSV or Excel: consumption per unit, or initial and final readings (in allocation units, kWh or m³). Before splitting:

• a final reading below the initial one is not a consumption: check it;
• if the printed consumption differs from the difference between readings, the difference applies — and it should be checked;
• a unit in the table without a reading would get a zero consumption share: check it;
• with no readings at all, the whole fuel goes on the table and the split stays to verify;
• if total consumption is zero, the whole fuel goes on the table.

#Owner and tenant

Heating — fuel and running — is the tenant's (art. 9 L. 392/1978), unless a different table applies.

#How the agent does it

The Condominium expense split agent reads the gas invoices, the heating table and the readings' CSV (tables and readings in Excel or CSV are read by code, not by the model). It splits the fixed and consumption shares with the regolamento's percentage — or the 30 % default, flagged to verify — and says where the percentage came from. The split is then approved by the assembly with the rendiconto; nothing goes to the owners.