Collective self-consumption: sharing the sun within 5 km

Updated 3 August 2026. We went and checked what you actually pay to share energy through the grid. The answer has a name —the TDA toll— and a value: zero on low voltage in 2026, but zero by arithmetic, not by exemption. Below we explain why, what could make it stop being zero, and why the factor that really decides a project is not this one but simultaneity.

More than 70% of primary homes in Spain are in multi-family buildings. Most have no roof of their own, or the one they have is small, shaded or shared with twenty neighbours. For years that meant being locked out of self-consumption. Collective self-consumption is the mechanism that turns it around: one generation installation, many associated consumers, and the distribution grid as the thread connecting them. And 2026 is the year this mechanism finally gets rules worthy of its potential.

What collective self-consumption actually is

The idea is simple: one solar installation (on a residential roof, an industrial unit or a municipal building) links its output to several consumption points, each with its own meter and its own contract. The energy generated is divided among the participants according to allocation coefficients that they have all signed in an agreement.

Every hour, the distributor applies those coefficients to production: the part that coincides with your consumption comes straight off your bill, and the part you are not using at that moment is compensated as surplus, at whatever price you have agreed with your retailer. Each participant settles individually; there is no need to share a retailer or a tariff.

Coefficients can be fixed (the same percentage every hour of the year) or vary by hour, an option the rules have allowed since late 2022 but that in practice few retailers and distributors handle with any agility. That detail, as we will see, is one of the keys to what comes next.

The race for metres: from 500 to 5,000

The constraint that has historically killed most projects is distance. Royal Decree 244/2019 set the initial limit at 500 metres between generation and consumption through the grid. RDL 18/2022 raised it to 1 km for rooftop installations, and RDL 8/2023 took it to 2 km for all technologies.

The big jump came in March 2026: Royal Decree-Law 7/2026 extends the radius to 5 km and treats as nearby installations associated through the grid any solar or wind installation of up to 5 MW located less than 5,000 metres from the associated consumers, within the same distribution area and connected at low or medium voltage.

In practical terms: the roof of an industrial unit at the edge of town can feed homes in the centre. A municipal building with a good roof can serve a whole neighbourhood. In a mid-sized town on the Catalan coast, a 5 km radius covers practically the entire municipality. Where project design used to begin by ruling participants out on metres, it now begins by counting usable roofs.

The other changes in RDL 7/2026

The decree does not only extend metres. Three further changes deserve attention:

The self-consumption manager. Created as a legal figure in the Electricity Sector Act: a person or company that represents the associated consumers and handles dealings with the distributor and the administration on their behalf. Until now, managing a collective of thirty neighbours meant thirty signatures for every change to the allocation agreement. This figure professionalises the management and is, most likely, the piece that will make large projects scalable.

Compatibility of modalities. The same consumer can now take part in two self-consumption schemes at once: the individual installation on their home and a nearby collective one, for example. Previously you had to choose.

Income-tax deductions. A 10% deduction for self-consumption installations (batteries included) on owned property, or 20% for owners of homes in predominantly residential buildings where the installation has been carried out. The maximum base is €5,000 a year and the installation must be completed within 2026: anyone still thinking about it has a deadline. For companies, free depreciation for renewable investments remains in place.

Worth recalling too is a provision that already existed and is often overlooked: the Horizontal Property Act allows renewable installations to be approved with the vote of one third of owners representing one third of the shares. Neither unanimity nor an absolute majority is needed to put panels on a communal roof.

The numbers on a typical case

Picture an industrial roof 3 km from a residential area, with 100 kWp installed. On the Mediterranean coast that is around 140,000 kWh a year. If 30 homes take part with an average coefficient of 3.3%, each household is allocated roughly 4,600 kWh a year.

With fixed coefficients and no battery, a household with moderate daytime consumption directly uses perhaps 40 to 50% of that energy (the rest is generated when nobody is home). Around 2,000–2,300 kWh self-consumed at an avoided price of €0.15–0.20/kWh comes to €300–450 a year; the remaining 2,300–2,600 kWh, compensated as surplus at around €0.02–0.05/kWh (with the solar pool at midday in 2026 often close to zero), adds another €50–120. All in, an order of magnitude of €350–500 a year per household, without having installed anything at home. That figure, however, depends heavily on the simultaneity we look at in the next section, and the real numbers will depend on the consumption profile, the tariff and how the coefficients have been designed: which is why designing the allocation matters as much as sizing the plant.

And here the structural limitation of the model appears: the bulk of generation is concentrated in the middle of the day, exactly when households consume least. Without storage, half the value is settled as surplus at a low price.

The toll for leaving the building

This is where it pays to be precise, because there is a great deal of confusion in both directions.

There is indeed a specific toll for going through the grid. Article 9.5 of the Electricity Sector Act provides that, where energy is transferred through the distribution grid, the associated consumers shall pay an amount for using it, and Article 17.5 of RD 244/2019 tasks the CNMC with setting it. And the CNMC has done so: Article 6.3 of Circular 3/2020 creates a whole family of tolls —2.0TDA, 3.0TDA and 6.1TDA to 6.4TDA— with energy terms that expressly apply to energy self-consumed in nearby installations through the grid. They have values published every year.

And their value for low voltage is zero. In the toll resolution in force since 1 January 2026, voltage level NT0 —up to 1 kV, where every household sits— appears with a dash across all periods. An industrial consumer connected at medium voltage taking part in the same collective scheme would pay around 1.4 cents for every kilowatt-hour self-consumed at peak; a household pays nothing.

On top of that, self-consumed energy does not pay ordinary tolls and charges either, because it is netted out before they are applied: RD 244/2019 makes them fall on "the individualised hourly energy consumed from the grid", which is total consumption minus self-consumption.

Adding it up: today, for a household on low voltage, a kilowatt-hour self-consumed through the grid pays no ordinary toll, no ordinary charge and no TDA toll.

That said, two warnings, and both matter.

First: that zero is calculated, not protected. Annex II of Circular 3/2020 splits network revenue between the power term and the energy term by voltage level, and it assigns NT0 100% to power and 0% to energy. Since the TDA toll is computed solely from the energy component of its own voltage level, on low voltage the formula returns zero by construction. This is not an exemption the legislator set out to shield: it is the arithmetic result of an allocation parameter. If the CNMC moves that 100/0 towards the 75/25 already applied at other levels, the 2.0TDA stops being zero without a single line of the law being touched. And the toll methodology is under review right now.

Second: what participants actually feel is not the tolls. Anyone already in a cooperative has the sense of paying for the shared kilowatt-hour as if it came from the other side of the world, and they are right about the sensation even though the cause is a different one. What happens is that only the part of your allocation that coincides with your consumption in that hour is netted off. The rest falls to surplus and is settled at around €0.06/kWh instead of the €0.17 that avoiding a purchase is worth. That simultaneity gap is worth on the order of €0.10/kWh: ten times more than any plausible TDA toll. That is where the value is lost, not in the tolls.

So it is worth not conflating four things that are often presented together as if they were a single wall:

1. Simultaneity, worth around €0.10/kWh and by some distance the dominant factor. You fight it with well-designed coefficients, shifting consumption and storage.
2. The fixed terms of your contract, which you keep paying in full whether you have self-consumption or not. You reduce them by adjusting contracted power.
3. The compensation cap, which can never exceed the value of the energy purchased within the billing period. Whatever is left over is lost. You fight it by sizing well.
4. The TDA toll, zero today on low voltage, but with the methodology open.

The first three are your design decisions. Only the fourth is regulatory risk, and today it is worth zero.

By contrast, when generation is connected to the internal network —to the building's meter room, or within the same cadastral reference— the shared kilowatt-hour never crosses a boundary meter. It generates no tolls, enters no billing circuit, is not taxed: it simply does not exist as far as the electricity system is concerned. It is energy at pure production cost.

That is where our design rule comes from, and we always apply it in this order: first, exhaust your own roof and the building's internal network; only then go looking for generation or consumers within the 5 km radius. The extension to 5 km is a magnificent tool for anyone with no alternative —the neighbour with no roof, the interior flat, the ground-floor unit— but it should never be the first option for someone with a residents' association and a usable roof over their head. The 5 km widen the market; the internal network maximises the return.

Where this could go

Anyone setting up a cooperative is amortising over twenty or twenty-five years, and so knowing what is paid today is not enough: they need to know which way the system is pushing. And here there are two signals worth not ignoring, both from the regulator and both from this year.

The first is about money. Reporting on the very rule that brought the 5 km, the CNMC warns the government that relaxing the requirements and admitting distributed storage "may bring to the surface a large body of consumers —difficult to quantify— that could affect the sufficiency of tolls and charges". And it puts a number on it: if the self-consumption targets in the national energy plan are met, revenue from the variable term of tolls and charges falls by €390 million in 2030 —€145m in tolls and €248m in charges— valued at 2026 prices. It adds that the figures could be higher still given the flexibility the rule introduces.

A hole that size gets plugged from somewhere, and the part needed to plug it is already built: the TDA toll exists, it has a structure, it has six periods and it has values published every year. For it to stop being zero on low voltage, no new law or royal decree is required; moving one allocation percentage inside a CNMC circular would be enough. As an order of magnitude, if low voltage were treated the same as medium we would be talking about €0.01–0.03/kWh at peak: small next to the €0.10 of simultaneity, but permanent and entirely outside your control.

The second is about the network. The CNMC has opened the door to limiting self-consumption spill because of imbalance risk, which adds a new unknown: not only what it costs to export, but whether you will be able to export it all.

And the historical pattern points the same way. Every extension of the distance has arrived with the preamble apologising: RDL 18/2022 warned that on low voltage the reasonable distances "without causing sharp voltage drops and high losses" are not large, and RDL 20/2022 called for "prudence in increasing this distance in order to avoid excessive losses". We have gone from 500 to 5,000 metres in four years while the regulator asked for restraint each time.

None of this means the 5 km are a bad idea. It means that the kilowatt-hour travelling over the public grid carries a risk profile that the internal-network kilowatt-hour does not, and that in a twenty-year project that weighs more than a few cents.

What is still missing: the distributed storage decree

The answer to that limitation lies in the draft Royal Decree on self-consumption and distributed storage that MITECO put out for public consultation in October 2025 and which, according to the ministry itself, should be approved this summer. Three elements of the text look decisive to us:

The shared surplus modality, which introduces the concept of shared hourly surplus energy: energy that a main consumer does not use will be redistributable among the other participants instead of being settled directly as surplus. It is the step from allocating blind percentages to allocating energy where each hour it is worth most.

Distributed storage associated with the consumer, configured as a connection type equivalent to any self-consumption modality, with the same administrative, technical and economic conditions. Translation: batteries behind the meter, in collective schemes too, will finally have an explicit regulatory home instead of living on interpretation.

And the development of the self-consumption manager's obligations, including notifying changes to the allocation agreement through a simplified procedure for installations under 100 kW on low voltage.

In parallel, a second draft royal decree, out for consultation until 13 July 2026, develops RDL 7/2026 for industrial settings and front-of-meter storage. The regulation is advancing in layers, and it is worth not losing track of any of them.

Where batteries fit (and why we are here)

Collective self-consumption without storage is a plant that gives value away during the sunny hours and has none at dinner time. With a properly sized battery alongside the generation, midday energy shifts to the evening, the fraction each participant actually uses rises, and dependence on the surplus compensation price falls. Add dynamic coefficients and smart hourly management, and the system can decide every hour whether the energy goes to the participants, to the battery or to the grid, depending on where it is worth more.

There is a second effect, less obvious and perhaps more important in the long run: energy that is stored and consumed behind the same meter never travels over the public grid. It pays no tolls today, it will pay none if they are tightened tomorrow, and it does not depend on whether exporting will be allowed. Every kilowatt-hour the battery shifts from midday to the evening is a kilowatt-hour that leaves the regulatory risk perimeter. That is not a sales argument: it is a direct consequence of how the rules are written.

This is not done with a spreadsheet: it is done with continuous telemetry of generation, consumption and battery state, and with algorithms that optimise the whole. It is exactly the management layer we develop at SolarBox, and the self-consumption manager figure created by RDL 7/2026 is the legal clothing this service was missing.

Our honest advice: if you live in a residents' association with a usable roof, start at home —internal network, no tolls, maximum return. If you have neither roof nor building to put one on, the 5 km radius is your way in, knowing that part of the value stays behind on the journey. In both cases, 2026 is the year to move: the tax framework expires on 31 December, the 5 km radius is already in force, and the decree that will regulate shared batteries is close. When the final text is published, we will analyse it right here.

In the meantime, if you would like to know what role your roof (or your consumption) could play in a collective self-consumption scheme, ask us for the free analysis: an electricity bill is enough to get started.