Which free tools does ekko publish?

Using ekko’s two calculators, the same building is compared when the heating is due for renewal, because at that point either option means buying equipment: replacing each flat’s own system, or installing a communal one and running the main pipework to every flat, keeping the radiators and each flat’s circuit. In Madrid, with 24 flats of 100 m², per flat over 15 years: with gas, €21,282 if each flat replaces its boiler and €23,098 with a communal boiler; with an air-to-water heat pump, €25,759 individual and €28,468 communal. These are averages over the 24 flats, ground and top floors included, with gas on Spain’s regulated tariff (TUR) in both cases: TUR.4 for the building and TUR.2 for each flat.

From how many flats does the communal system pay off? With gas, in Seville (climate zone B4), from 56 flats; in Badajoz (C4), from 72; in Madrid (D3), from 100; and in Burgos (E1), from 100. With a heat pump, in Seville, from 24 flats; in Badajoz, from 64; in Madrid, not even with 200; and in Burgos, not even with 200. That is the size from which the communal system is cheaper in every building compared: one block of 4 storeys, like the calculator’s, in steps of 4 flats up to 200, in one provincial capital per winter climate zone of Spain’s Building Code, from the mildest to the coldest. With gas, a smaller size can also come out in its favour, depending on which band of the regulated tariff the building’s consumption falls into.

A communal system shares the plant room, the design and the maintenance among all the neighbours, which is why it improves with every flat added. But switching to it means running pipework to every flat — the calculator allows €1,200 per flat — and it loses heat in the shared pipes — 12% of the heating and 25% of the hot water in the calculator — and it adds meter reading, management and insurance. The more the heating is used, the more those losses weigh: that is why the threshold rises with the cold.

On emissions, a communal system only helps if the energy source changes. With the same one, it uses more: in Madrid, the communal boiler burns 18% more gas per flat than individual ones (12,149 against 10,265 kWh a year), the heat lost in the network. What cuts emissions is to stop burning gas: each flat’s boiler emits about 1,868 kg of CO₂ a year (0.182 kg/kWh, the emission factor published by Spain’s Ministry for the Ecological Transition), and a heat pump, communal or individual, burns nothing in the building. To emit as much, each kWh of electricity would have to emit 0.49 kg of CO₂, and in 2025, almost 75% of Spain’s electricity was generated emission-free (Red Eléctrica, provisional figures of 19 December 2025). If the aim is to stop burning gas, in Madrid it is cheaper for each flat to install its own heat pump (€25,759 per flat) than to build a communal one (€28,468), and it uses less electricity; staying with a gas boiler in each flat costs €21,282.

The decision belongs to the owners’ meeting, not to each household. Installing communal gas heating needs the votes of three fifths of the owners, who must also hold three fifths of the ownership shares (article 17.3 of the Spanish Horizontal Property Act). A communal heat pump, being renewable, needs only a simple majority if the yearly amount charged to each owner, after grants and financing, does not exceed twelve ordinary monthly service-charge payments (article 17.2); it can also be agreed by one third, but then those who did not vote in favour do not pay (article 17.1). Once installed, communal heating must measure each flat’s consumption with meters or heat cost allocators, except in climate zones α, A and B (Royal Decree 736/2020); that cost is included in the figures. Not included: finding room for the plant or the outdoor units, or the communal boiler’s flue.

Using ekko’s two calculators, the same building is compared when the boiler is due for renewal: keeping the communal system, with a new heat generator plus the heat cost allocators, valves and hot-water meters required by Royal Decree 736/2020, or each flat installing its own boiler or heat pump. In Madrid, with 24 flats of 100 m², per flat over 15 years: with gas, €21,778 communal and €23,528 individual; with an air-to-water heat pump, €27,148 communal and €26,443 individual. These are averages over the 24 flats, ground and top floors included, with gas on Spain’s regulated tariff (TUR): TUR.4 for the building and TUR.2 for each flat.

Going individual includes dismantling the communal system, at the amounts the community calculator uses for the same items: €1,500 to remove the equipment and dispose of the waste, €3,000 of building work in the plant room, €3,500 for the design and registration of its decommissioning, and €350 per flat to cut its connection to the shared network. For 24 flats that is €16,400, €683 per flat, on top of bringing gas to each flat — riser, branch, indoor pipework and connection, about €1,563 per flat — and the boiler or heat pump itself. With heating oil, emptying and removing or making safe the tank is quoted separately.

From how many flats is it worth keeping the communal system? With gas, in Seville (climate zone B4), from 12 flats; in Badajoz (C4), from 16; in Madrid (D3), from 32; and in Burgos (E1), from 36. With a heat pump, in Seville, from 16 flats; in Badajoz, from 24; in Madrid, from 36; and in Burgos, not even with 200. Below those sizes, going individual is cheaper, except for the odd size with gas, depending on which band of the regulated tariff the building’s consumption falls into. They are the sizes from which the communal system is cheaper in every building compared: one block of 4 storeys, in steps of 4 flats up to 200, in one provincial capital per winter climate zone of Spain’s Building Code. If the system distributes heat through risers that pass through several flats instead of one circuit per flat, each flat also needs its own circuit (€2,450 in the calculator) and the communal system pays off sooner: with gas, in Seville, from 12 flats; in Badajoz, from 12; in Madrid, from 12; and in Burgos, from 24; with a heat pump, in Seville, from 12 flats; in Badajoz, from 16; in Madrid, from 20; and in Burgos, from 92.

Keeping the communal system avoids bringing gas to every flat and dismantling the plant room, and shares the boiler and its maintenance among everyone: that is why it wins above a certain size. Against it, it loses heat in the shared pipework — the calculator assumes 12% for heating and 25% for hot water — and adds meter reading, management and insurance. The colder the climate, the more those losses weigh and the more flats it takes to offset them; with a heat pump, in Burgos one per flat is cheaper even with 200.

On emissions, going individual with the same energy source saves little: in Madrid, the flats’ boilers burn 16% less gas than the communal one (10,265 against 12,149 kWh per flat a year), the heat lost in the network, but they still emit about 1,868 kg of CO₂ per flat a year, against 2,211 (0.182 kg/kWh, the emission factor published by Spain’s Ministry for the Ecological Transition). What changes emissions is the energy source: with a heat pump, communal or in each flat, the building stops burning gas. To emit as much as the communal boiler, each kWh of electricity would have to emit 0.58 kg of CO₂, and in 2025, almost 75% of Spain’s electricity was generated emission-free (Red Eléctrica, provisional figures of 19 December 2025). In Madrid, renewing the communal system with a heat pump costs €27,148 per flat over 15 years and one in each flat €26,443, against €21,778 for staying with the gas boiler.

Removing communal heating needs the votes of three fifths of the owners, who must also hold three fifths of the ownership shares (article 17.3 of the Spanish Horizontal Property Act); installing heat pumps for individual flats can be agreed by one third (article 17.1). If it is kept, Royal Decree 736/2020 requires individual meters or heat cost allocators wherever this is technically feasible and the investment pays back in four years or less (Annex III), except in climate zones α, A and B: Seville (B4) is exempt; Badajoz (C4), Madrid (D3) and Burgos (E1) are not. Individual boilers must vent their flue gases through the roof, with a new flue if there is none; Spain’s thermal installations regulation (RITE, IT 1.3.4.1.3.1) only allows a façade or a ventilation shaft for room-sealed gas boilers of 70 kW or less in NOx class 5. The figures do not include those flues or the work for the heat pumps’ outdoor units.