Solar panel installation in Playa de San Juan

Playa de San Juan is the beachfront district of Alicante city, built almost entirely as mid-rise and high-rise apartment blocks.

One roof serving thirty or sixty flats changes the whole shape of a solar project here.

What an apartment block can realistically do with one roof

The building stock here is the constraint. A block of forty flats has one roof, and that roof physically cannot host forty individual installations of a useful size. Whatever happens on it is a shared decision, and the useful question is not "can I put panels up there" but "what is the installation for".

The most straightforward version is a communal installation supplying communal consumption: lift, stair and garage lighting, garage doors, pumps and any communal air conditioning. Those loads run during the day, they are predictable, and the community pays for them collectively already. A modestly sized array covering them is the easiest solar project to get agreed in a block like this, because everybody benefits proportionally and nothing has to be divided.

The more ambitious version is shared self-consumption, where a single installation is divided between participating flats according to agreed coefficients. It is technically well established and it is what allows an individual flat in a block to benefit from solar at all. It needs more agreement up front, because the coefficients have to be set and the participants defined, and in a district where many owners are non-resident that takes time.

What an individual flat cannot usefully do is treat a communal roof as private space. Where a block already has equipment, terraces in private use, or a roof with limited structural capacity, the available area shrinks quickly, and it is better to establish what is genuinely usable before anyone designs anything.