Commercial solar allows a business in Spain to generate electricity at its premises and use that power while it is being produced. Panels may be installed on a warehouse, factory, hotel, office, car park canopy or suitable land connected to the business.
During daylight hours, the system supplies part of the building's immediate demand. The electricity grid supplies any shortfall. If the panels generate more than the business is using, the surplus can be prevented from entering the grid, stored in a battery, compensated through the electricity bill where the installation qualifies or sold under the applicable producer arrangements.
The equipment operates automatically once the installation has been commissioned. The commercial result depends on how closely solar production matches the times when the business consumes electricity.
How electricity moves through a commercial solar system
Photovoltaic panels generate direct current electricity when exposed to daylight. One or more inverters convert this into alternating current suitable for the building's electrical system.
In a conventional grid-connected installation:
- The panels generate electricity during daylight hours.
- The inverter converts the output into usable alternating current.
- The business consumes available solar electricity as part of its immediate demand.
- The grid supplies any additional electricity required.
- Unused generation is handled according to the system's export and storage arrangements.
- Monitoring equipment records generation and system performance.
The business normally remains connected to the grid. Solar reduces imported electricity during generating hours, but the building can still draw power at night, during poor weather or whenever demand exceeds production.
Consider a business using 180 kW at a particular moment. If its solar installation is producing 120 kW, the remaining 60 kW comes from the grid. If demand falls to 80 kW while generation remains at 120 kW, there is 40 kW of surplus. That surplus is exported, stored or curtailed according to the system design.
These flows change continuously as production and consumption rise and fall.
Why on-site consumption matters
Spanish law defines self-consumption as electricity used by one or more consumers from an associated generating installation close to the point of consumption. The main technical and economic framework is established by Real Decreto 244/2019, as subsequently amended.
For most businesses, the greatest financial value comes from solar electricity consumed on site as it is generated. Each unit used directly reduces the amount of metered electricity imported from the grid at that time. Its precise value depends on the supply contract, tariff period and applicable variable charges.
Surplus electricity can still have value, but it should be modelled separately. The value received for exported power may be lower than the cost avoided by using that electricity within the business.
This is why a commercial installation should be designed around the consumption profile rather than the maximum number of panels that will fit on the roof.
A warehouse with little daytime activity may have an enormous roof and relatively modest demand. A hotel, supermarket, cold store or continuously operating factory may use substantial electricity throughout the solar-generating period. The second property may be able to use a much larger share of its output directly.
Roof area matters. The relationship between generation and demand usually matters more.
Spanish business tariffs affect the calculation
Many commercial supplies in Spain use tariffs with six time periods, P1 to P6, for energy and contracted capacity. The applicable tariff depends principally on connection voltage and, for low-voltage supplies, contracted capacity.
Under CNMC Circular 3/2020:
- 3.0TD applies to supplies connected at no more than 1 kV when contracted capacity exceeds 15 kW in any period.
- 6.1TD applies to supplies connected above 1 kV and below 30 kV.
- Higher-voltage commercial and industrial supplies fall within the other 6.XTD categories.
The period assigned to a particular hour varies by season and geographical electricity system. Saturdays, Sundays and national public holidays are generally assigned to P6 throughout the day. Contracted capacities must also be non-decreasing from P1 to P6.
Solar generation often overlaps with higher-value daytime periods, but the saving cannot be calculated accurately from a single national electricity price. A credible assessment maps expected generation against the site's actual interval consumption, tariff calendar and electricity contract.
A five-day operation may also generate a greater proportion of surplus at weekends when the premises are lightly used. Annual consumption figures can hide this difference.
Commercial tariffs deserve detailed treatment in their own right. Their role here is simple: the same quantity of solar electricity can have a different financial value depending on when the business would otherwise have imported it.
How a commercial solar installation is sized
The starting point is the business's electricity data.
Annual bills show how much electricity has been purchased, but they provide only a limited picture of when that electricity was used. Interval data makes it possible to compare demand with expected solar generation across working days, weekends and seasons.
An initial assessment normally considers:
- Annual and monthly electricity consumption
- Consumption during working hours
- Weekend, holiday and seasonal demand
- Maximum demand and contracted capacity
- The applicable electricity tariff and contract
- Planned changes to equipment or working hours
- Available roof, car park or land
- Orientation, shading and roof pitch
- Roof condition and structural capacity
- Electrical infrastructure and connection voltage
- The proposed treatment of surplus electricity
- Whether storage or backup power is being considered
Where available, consumption data can be obtained through the electricity distributor or platforms such as Datadis using the supply point's CUPS reference. The required data interval depends on the metering arrangement and project size.
The designer then models expected generation at the site and compares it with the demand profile. A useful proposal distinguishes between total generation, solar electricity consumed on site, surplus exported or curtailed and electricity still imported from the grid.
It should also disclose the assumptions used for system losses, panel degradation, future electricity prices, maintenance and equipment replacement.
A proposal based only on roof area or annual consumption may recommend a system that generates more surplus than the business can use or monetise effectively.
Commercial solar without surplus
A self-consumption installation without surplus uses an anti-export or zero-export system. This prevents electricity from being injected into the distribution network.
A controller monitors the flow of electricity at the grid connection point. When solar output approaches the building's immediate demand, the controller reduces inverter output so that power does not pass into the grid.
This arrangement can be suitable when export capacity is unavailable, the business has strong daytime consumption or export income is not important to the financial case.
Spanish regulations exempt self-consumption installations without surplus from obtaining grid access and connection permits. The installation still has to comply with the relevant electrical, safety, municipal and regional requirements.
Repeated curtailment should be examined. It may indicate that the system is oversized for the present demand unless planned expansion, electrification or battery storage justifies the additional capacity.
Commercial solar with surplus
A system with surplus can export electricity that the business does not consume when it is generated.
There are two main economic routes: simplified compensation and the sale of surplus electricity.
Simplified compensation
The simplified compensation mechanism is available when the relevant statutory conditions are satisfied. These include renewable generation with installed capacity no greater than 100 kW.
Qualifying surplus is valued through the electricity billing process. It is a compensation arrangement rather than an unrestricted electricity sale. A consumer using simplified compensation cannot sell the same surplus through the market mechanism at the same time.
MITECO explains the eligibility conditions and billing treatment in its official self-consumption questions and answers.
Sale of surplus electricity
A business may instead sell exported electricity. The installation is then treated as an electricity producer for that exported energy and the corresponding registration, market, tax, metering and representation requirements apply.
This route may be relevant when the installation is above the simplified-compensation threshold or when significant export forms part of the proposed model.
The financial assessment should distinguish between the value of electricity used within the business and the net value of electricity exported after applicable costs and obligations.
What changes above 100 kW?
The 100 kW threshold affects the available compensation and administrative arrangements. It is not a general maximum size for commercial self-consumption.
MITECO confirms that the self-consumption framework does not impose an overall maximum capacity. The practical limits arise from the property, electrical installation, safety requirements, grid conditions and project economics.
For photovoltaic systems, installed capacity under Real Decreto 244/2019 is based on the maximum capacity of the inverter or the combined maximum capacity of multiple inverters.
A system above 100 kW cannot use standard simplified compensation. Depending on its design, it may consume the electricity on site, operate without surplus, export under the relevant sale arrangements or use storage and controllable loads to increase on-site consumption.
Larger installations can require more extensive engineering, network studies, protection equipment, metering and administrative work. An industrial system should be procured as an engineered commercial project rather than treated as a larger version of a domestic installation.
Collective self-consumption and the 5 km rule
Commercial solar does not always have to be limited to one consumer using panels installed on its own building.
Real Decreto-ley 7/2026 expanded the proximity provisions for certain network-associated self-consumption arrangements. A photovoltaic or wind installation with capacity up to 5 MW can qualify as a nearby associated installation through the network when it is less than 5,000 metres from the associated consumers, subject to the full legal and technical conditions.
This creates additional possibilities for industrial estates, business parks and organisations with unsuitable roofs. A single installation may now be capable of participating in a collective self-consumption arrangement serving several nearby businesses, subject to connection, metering, contractual and administrative requirements.
The same legislation introduced the gestor de autoconsumo role to support the administration of collective arrangements on behalf of participating consumers.
Collective self-consumption is a distinct project structure. A business should not assume that geographical proximity alone makes a site eligible.
Does commercial solar work during a power cut?
A standard grid-connected commercial solar installation normally shuts down when the grid fails. Anti-islanding protection prevents the system from energising grid infrastructure while engineers may be working on it.
Panels on the roof do not automatically provide backup electricity during an outage.
Maintaining selected loads requires a system designed for backup operation. Depending on the project, this can involve compatible inverters, battery storage, automatic isolation from the grid, backup distribution boards, load prioritisation and additional switching and protection equipment.
The business should identify which loads have to remain operational and for how long. Supporting emergency lighting, communications and control systems is a different design problem from running refrigeration, production machinery or a complete hotel.
Backup capability needs to be specified during design. It cannot be assumed merely because the installation includes panels or batteries.
Are commercial batteries necessary?
No. Many commercial solar installations work effectively without storage.
A business with strong and consistent daytime demand may already consume most of its solar generation directly. A battery might add cost without improving the financial result enough to justify it.
Storage can merit closer assessment when substantial generation would otherwise be exported or curtailed, consumption remains high after sunset, backup has operational value or controllable storage could help manage demand peaks.
Battery analysis should cover usable capacity, power rating, expected cycling, degradation, warranty conditions, fire safety, control strategy and replacement expectations. The presence of surplus electricity alone does not establish that a battery is financially appropriate.
Does solar reduce the whole electricity bill?
Solar reduces the amount of electricity imported while the installation is generating and the business is consuming power. It does not automatically remove every element of the bill.
The business may continue to pay:
- Contracted-capacity charges
- The cost of electricity imported from the grid
- Applicable taxes
- Reactive-energy charges where relevant
- Supplier and metering charges
- Charges created by demand above contracted capacity
A standard photovoltaic system should not be relied upon to reduce contracted capacity. The business may record its maximum demand when solar output is low, during poor weather or outside daylight hours. Capacity optimisation and battery-controlled peak management are separate exercises.
What permissions and registrations are required?
The route depends on system size, export mode, voltage, connection arrangement, autonomous community and municipality.
A commercial project may involve:
- Municipal works or planning procedures
- Electrical design documentation
- A structural assessment
- Grid access and connection procedures
- Applications to the distribution company
- Installation certificates
- Inspection by an authorised control body where required
- Registration or legalisation through the autonomous community
- Changes to supply or access contracts
- Producer registration and market arrangements where electricity is sold
Installations without surplus are exempt from grid access and connection permits. Certain surplus installations of 15 kW or less on qualifying urbanised land are also exempt. Most larger commercial projects that export electricity should expect a formal grid process.
Administrative procedures vary between autonomous communities. IDAE's professional guide to processing self-consumption installations covers the main procedures and includes regional information.
The installer or project engineer should establish the applicable route before the business relies on a delivery programme or financial forecast.
Can a tenant install commercial solar?
A tenant may be able to install solar on leased commercial premises, but the arrangement must be agreed with the property owner.
The parties need to determine:
- Who owns the equipment
- Who is responsible for the roof and its warranties
- Whether structural works are permitted
- What happens to the system at the end of the lease
- Who receives any exported-energy income
- Whether the remaining lease term supports the investment
Where the lease is short or the roof cannot be used, third-party ownership, a power purchase arrangement or collective self-consumption may offer alternatives. Each creates different contractual, tax and regulatory obligations.
How a commercial solar project proceeds
Initial energy assessment
The business supplies electricity bills, available interval data, site information and details of its operating pattern. This establishes whether there is a credible project before detailed engineering begins.
Site and roof survey
The survey examines the available area, access, shading, electrical infrastructure, cable routes, switchgear and proposed mounting surface.
For rooftop systems, structural capacity is fundamental. Older industrial premises may also contain asbestos materials or fragile roof elements that affect the design and programme.
System design and financial modelling
The designer matches the proposed capacity to consumption, available space and the selected export arrangement. The financial model should disclose its assumptions rather than present a single unexplained payback figure.
Permissions and connection work
Technical documentation is prepared and the applicable municipal, regional and distribution-company procedures are completed. This stage can have a substantial effect on the programme, particularly for larger exporting systems.
Installation and commissioning
Mounting equipment, panels, inverters, cabling, protection, monitoring and any storage equipment are installed and tested. Commercial work may be phased to reduce disruption to production, customers or site access.
The required certificates, inspections, contracts and registrations are then completed according to the project route.
Monitoring and maintenance
The operating system should be monitored against expected performance. Inverter data, meter readings and alerts can identify faults, changes in consumption or declining output.
Maintenance requirements depend on the site. A dusty agricultural building, coastal hotel and urban office roof will not necessarily need the same inspection and cleaning schedule.
What determines whether commercial solar is worthwhile?
Spain has a favourable solar resource, but the quality of the investment depends on the individual site and the proposed system.
The assessment needs to consider daytime demand, electricity-contract terms, available area, structural constraints, electrical infrastructure, grid capacity, project cost, financing and the proportion of generation used on site.
It should also account for the value of surplus electricity, maintenance, equipment replacement, tax treatment, the expected ownership period and planned changes to the premises.
Future electrification can alter the result. Fleet charging, heat pumps, cooling, process equipment or business expansion may increase daytime demand. Those changes should appear in the model only when supported by credible plans.
The useful first step is a consumption-led assessment that establishes a likely system range, expected on-site use, surplus position, physical constraints and regulatory route before a full quotation is prepared.
Frequently asked questions
Can a business use solar power and grid electricity together?
Yes. Solar supplies part of the building's immediate demand and the grid supplies any shortfall. The balance changes automatically throughout the day.
Can commercial solar panels supply all of a business's electricity?
They may cover a large share of daytime demand, but the result depends on consumption, available area and operating hours. Most grid-connected businesses still import electricity at certain times.
Can a business sell unused solar power in Spain?
Yes. Surplus can be sold under the applicable producer and market arrangements. Qualifying renewable installations no greater than 100 kW may instead use simplified compensation through the electricity bill.
Is there a maximum size for commercial self-consumption in Spain?
Spanish self-consumption rules do not impose a general maximum capacity. Property, structural, electrical, safety and grid constraints still apply.
What changed for collective self-consumption in 2026?
Real Decreto-ley 7/2026 expanded the network-proximity criterion to 5,000 metres for qualifying photovoltaic and wind installations up to 5 MW. It also introduced the gestor de autoconsumo role.
Will commercial solar keep a business running during a blackout?
A standard grid-connected installation normally shuts down. Backup operation requires compatible equipment, safe grid isolation and usually storage designed for the required loads.
How is the correct system size calculated?
The designer compares expected solar generation with interval consumption, operating hours, tariff periods, available area, electrical capacity and the proposed treatment of surplus.
How long does a commercial solar project take?
The programme includes data analysis, surveys, engineering, permissions, connection procedures, procurement, installation, inspection and legalisation. Project size and export arrangements can materially affect the timetable.
Does commercial solar require batteries?
No. Batteries are optional. Their value depends on the timing of consumption, surplus generation, tariffs, demand peaks and whether backup power is required.
Planned internal links
Add these links when the supporting pages are published:
- Commercial solar costs in Spain
- Commercial solar ROI and payback
- Commercial solar system sizing
- Commercial solar feasibility studies
- Commercial solar permissions in Spain
- Commercial solar systems above 100 kW
- Commercial solar with and without surplus
- Commercial battery storage
- Spanish business electricity tariffs
- Commercial solar financing and PPAs
Suggested royalty-free image
Warehouse roof with commercial solar panels
Pexels presents this photograph as free to use. It shows a commercial rooftop installation rather than a domestic property or utility-scale solar farm.