Frequently askes questions

It is the ability of one or more consumers to generate, manage and consume energy in the same location or remotely, whether with or without energy accumulation. Each kWh produced and self-consumed is 1 kWh less that we must buy from the electricity company with its corresponding savings on the electricity bill.

Solar panels generate direct current that is received by the inverter, which transforms it into the alternating current that we consume at home.

We inject the generated solar energy (in most cases) directly into the main electrical panel of the house, so that if at a given time we are generating 3 kWh and consume 4 kWh, then the first 3 kWh of consumption will come from the solar panels we will buy the kWh that remains to complete consumption from the electricity company.

And also the other way around, if at a given hour we are generating 3 kWh, and we are only consuming 2 kWh, then the entire consumption will come from the solar panels and the excess solar kWh will be sent to the grid.

For this kWh that we send to the grid, the electricity company will apply a discount to our electricity bill (compensation).

In those self-consumption facilities with less than 100 kW of power and that are connected to the internal network of any of the consumers associated with the generation facility, the electricity company will value the surpluses (leftovers) that we send to the distribution network in accordance which is called simplified compensation mechanism.

Of the energy produced by the photovoltaic installation, the energy that cannot be self-consumed at the moment (solar surplus) will go to the electrical grid and the bidirectional meter of the marketing company will count hourly the total energy sent (exported) into the grid. of distribution.

Each electricity distribution company values the kWh sent to the network at a different price, adding their value during the month.

At the end of the month, when we receive the invoice, we will see a discount line with the total economic value of the kWh sent to the grid.

The electricity bill can never be negative, and therefore if the installation has many surpluses, a part of these may not be able to be valued and may be lost.

It is important to keep in mind that the value they give us for the surplus is always lower than the value we pay for the electricity consumed, and therefore we will always have maximum profitability and lower payback with installations with little surplus.

However, if we try to make an installation without surpluses, the resulting installation may be very small, and therefore the savings in absolute value will also be lower.

Therefore, the most appropriate thing is always to achieve an optimal balance between profitability (small installation with little surplus) and savings (larger installation with more surplus) that satisfies the client's needs, each client is different.

If we install a battery we reach the maximum value for each kWh generated, since we value all the kWh generated at the price we buy electricity at home. To achieve this maximum value, it is necessary to invest in the battery, which generally represents an extra cost of between 60% and 70% compared to the installation without a battery.

On the contrary, if we do not install the battery, the surpluses that would go to the battery will be sent to the electrical grid and will be compensated/valued at a lower price than if we had saved them. The advantage of not installing the battery is that you save that 60% - 70% extra cost.

If we think about buying a battery in economic terms, the amortization of the installation may be longer, but in any case the economic factor is not always decisive, since there are many people who buy batteries from us because they want to achieve maximum autonomy with respect to the electricity company. .

Furthermore, we must not forget that as more solar systems are installed, the price of electricity during the day will fall and at night it will be more expensive, and therefore it will be more profitable to install batteries.

There are other storage systems to store surpluses. We have surplus diverters (Fronius and Lacecal for example), which when they detect that solar generation is lower than consumption, they divert the surplus to an electrical resistance located inside a hot water tank, so that the water is preheated. coming from the street before reaching the boiler/water heater and thus the thermal jump necessary to heat it is reduced.

Batteries store energy in the form of chemical energy and DHW accumulators in the form of thermal energy.

Another solution for those who have an electric car and a possible charging point is to install an electric vehicle charger (EVC) that allows them to take advantage of solar surpluses.

A solar installation currently has a proven life of more than 25 years. Consider that a solar installation does not have moving mechanical parts that suffer wear, or circulating fluids that cause overpressures as occurs with solar thermal energy. Therefore, if the installation has been well designed, it is very reasonable that the useful life should be greater than 25 years.

The modules degrade over time and lose production capacity, however manufacturers give a minimum production guarantee of 80% after 25 years; That is to say, they assure that after 25 years, the solar panels will produce at least 80% of what they produce on the first day.

Additionally, the panels have a product warranty of at least 12 years against manufacturing defects.

Current inverters have a useful life of more than 15 years and the inverters we offer have a 10-year warranty.

Battery: the most common batteries for solar installations are lithium iron phosphate (LiFePO4) and usually have a 10-year warranty and a useful life of more than 6,000 cycles (16 years).

The structures we offer generally have a 10-year warranty.

In addition, we as an installation company offer a 5-year installation warranty, far beyond the 2 years required by law that most installation companies offer.

The best maintenance that your solar installation can have is to have a good monitoring system that allows you to know that your solar installation is producing correctly at all times.

The only maintenance task that may be advisable is to try to clean the solar panels from time to time (mud and bird deposits). In any case, only clean the panels if access is sufficiently secure.

Generally, rainwater already cleans the panels since a 5° inclination of the panels is more than enough for the water to remove dirt from the solar modules. Residential installations typically have between 10° and 15°.

Rather than paying in advance for a maintenance service that will eat up part of the annual savings, we recommend keeping a good track of production and, if necessary, hiring our after-sales service.

We are currently preparing a premium monitoring solution that will allow us to carefully monitor production and set a few alarms that will alert us of any anomaly.

Current regulations require solar installations to stop working when they do not detect mains voltage for safety reasons.

Imagine that the electricity company wants to carry out maintenance work on the distribution network and cuts off the power supply to the entire street. If the solar installations were to continue to operate, they could cause electricity to flow back into the grid, which would endanger the workers who are working.

Translated with DeepL.com (free version)

There are backup solutions that allow the solar installation to continue working in case the power goes out to the house; However, these solutions involve installing a battery and permanently having a certain amount of energy available in the battery in case the backup system must operate.

These systems ensure an effective disconnection from the electrical grid, so the solar installation begins to function as an isolated system that cannot send energy to the grid.

In any case, this is problematic because the batteries have a high cost and if it also turns out that you can only use 50% because the other 50% must be saved in case the backup system has to start working, then the battery is even more expensive.

Therefore, our recommendation is not to consider backup systems if you do not have problems with frequent power outages.

If your doubt is between installing 10 or 12 panels at home, we will always recommend installing 12 panels and not precisely because we make a living installing 2 more panels.

The fact is that the marginal cost of adding 2 more panels now is minimal compared to the cost of adding 2 panels once the installation has been completed and legalized, since then we will have to move again, disconnect the roof wiring and reconnect it with the two additional panels, modify the project, carry out a new legalization, etc.

We are increasingly moving towards an electrification of demand with the arrival of the electric vehicle, aerothermal energy, etc... and therefore it is logical to think that in the future your electrical consumption will increase.

We recommend installing two more panels.

It makes sense if you are clear that in the future you are going to consume more, but again we must remember what we said in the previous point; Adding 4 more panels in the future will always cost significantly more than if you install them now.

With the appropriate drill bit, the tile is drilled in its highest part until you reach the structural part of the roof below, whether it is made of mesh or concrete. It is in this structural part under the tiles where the screws that support the aluminum structure and the solar panels are attached. The tiles are therefore only pierced by the fastening screws that have a flat rubber gasket that is tightened with a female over the hole, giving it the tightness that will obviously prevent possible leaks.

Furthermore, since all the holes are below the modules, which act as a roof, and water never runs through the highest part of the tiles, they will not even get wet.

If your installation is up to 15 kW, in most cases you will not have to ask Endesa for connection permission.

However, if your facility is not located on urbanized land and has the basic facilities and services required by urban planning regulations, it will be necessary to request a connection study from the distribution company in the area, which has a cost of €100 + VAT

Furthermore, in these cases, it will be necessary to process a technical access contract with the distribution company, which regulates the technical conditions of connection to the distribution network. This is not an economic contract.

First of all, we must process a prior notice of works and we will have to pay the construction and works tax (ICIO), which has an approximate cost of 4% of the cost of the work before VAT (it depends on the tax ordinances of each town council). .

In any case, most town councils have a bonus of 95% of the tax value for those projects that incorporate solar panels into the home. We process this bonus.

In addition, you will have to pay the urban planning license fee, which costs approximately 1.5% of the cost of the work before VAT (normally between €50 and €100).

Some municipalities also ask to deposit a small deposit for the management of the debris, which is returned upon completion of the work and to present the certificate from the waste manager who has received the debris.

Once the prior works communication has been processed, we must open the work center in case there is ever a work inspection or a serious accident occurs on the work site. This procedure has no cost, but it has a very high price if they hook you into working without having completed the procedure.

Now we can begin the installation, although some town councils illegally process what they call a deferred works statement that forces us to wait for its resolution due to the approval of the previous works statement.

Once the installation is done, we will begin the legalisation procedures; Firstly, the registration of the installation in the Registry of Technical and Industrial Safety Installations (RITSIC) at no cost, and finally the registration in the Self-Consumption Registry of Catalonia with a cost of €32.

All residential installations carried out until 31/12/2023 have the possibility of deducting 40% of the investment (with a maximum of €3,000) if they demonstrate with an energy certificate prior to installation and a subsequent one, that they have achieved savings 4'% of non-renewable primary energy.

It can also be achieved if you achieve an A or B energy classification in the energy certificate after installation.

Now, achieving these savings solely with solar installation is frankly complicated, since they can normally be achieved when acting on the thermal envelope of the building or making investments in the air conditioning system by installing aerothermal heaters.

Virtual batteries are a mechanism by which energy retailers keep your surplus and compensate you for the full price of the energy that remains in future bills without price limitations and even allow the surplus to be assigned to different locations.

A priori it seems like a very good idea, since you can value the excess kWh at the same price as if you stored them in a physical battery but without having to make the investment.

However, if the rate of solar installations continues to grow in the current way, in the end the price of energy in solar time will fall so much that it will be impossible for marketers to allow you to compensate for these surpluses with energy consumed in expensive hours (night).

Therefore, it is a good possibility in the short term, but in the medium-long term, the future of accumulation will surely go through physical batteries.

A collective self-consumption installation is the sum of "n" individual installations that share a series of common infrastructures: a single project, a single wiring, a single inverter, a single legalization and processing.

For this reason, it will be necessary to sign a sharing agreement between all participants in the collective self-consumption facility that will establish what % of the facility each participant has.

From here we must understand that sharing energy is a virtual phenomenon in which we do not really know where the electrons physically go.

For this reason, in a collective self-consumption installation it will be necessary to install a generation meter that will read and inform the distribution company of all the energy generated.

The distribution company will apply the distribution coefficients of the agreement and will allocate to each participant the corresponding part of generation. From here it will compare the generation with the consumption read by the consumption meters of each participant and will make the corresponding balance to end up billing each one for the difference between their consumption and their generation, and in case this difference is less than 0 applying the corresponding surpluses.

Currently the maximum straight line distance in the orthogonal plane between the generation meter and the consumption meter is 2 km.

Energy can be shared in both LV and MV.

No. You can share a facility with your neighbours', and therefore you will share all the energy generated (self-consumed and surplus), but you cannot share only your surplus.

Orienting the modules to the north will always be the last option, but if it is not possible to orient the modules to the south because we do not have space, or because we need to put more power to cover consumption and we do not have east-west options, then we will orient the panels to the north. without any problem.

It must be taken into account that panels facing north in Catalonia produce approximately 10% less than modules facing south to Germany.

At SolarTradex it is a very bad option, for the following reasons:

Esthetic. We need to make PV sexy, and seeing a house with raised panels on a sloping tile roof is just the opposite.

It is dangerous: we are experiencing more and more extreme weather conditions and placing elevated panels on a sloping roof only increases the wind load and plays with fire so that the installation flies away on the day you least expect it.

The Urban Planning Law does not allow it, since the urban planning of the municipality where they are installed would have to be modified. Installation on the roof of buildings and other auxiliary constructions, including car park pergolas, is only permitted when the installations do not exceed one meter in height from the flat roof or, in the case of a sloping roof, when the collectors or panels are located attached in parallel.

If we want to maximise solar generation, today it is much more profitable and safe to install a couple more solar panels in a coplanar arrangement facing east or west, since the price of solar panels has dropped very significantly and the cost of the structure It will also be cheaper.

Possible certainly, intelligent no. If you want to disconnect, you will have to size the installation to guarantee at least 3 days of autonomy, and that means having to make the installation larger and install batteries large enough to store energy for 3 days.

In addition, you will have to install a backup generator set in case, for example, in winter, we have bad weather for a week without being able to charge the batteries.

Obviously this is much more expensive than installing a self-consumption installation with network support.

Furthermore, having an isolated installation means always being aware of consumption and battery charge, and this goes against comfort, since you cannot come home and turn on the air conditioning as and when you want, you cannot bathe in the bathtub with candles, etc… you know what I mean.

It is a very common question asked by anyone considering installing solar panels at home, and the answer is yes, except in exceptional cases. The most common photovoltaic panels on the market today are manufactured in compliance with specific regulations regarding large impacts to the glass.

The modules are made of tempered glass, thermally processed to obtain greater resistance than conventional glass. They must pass hail impact tests, which according to the IEC 61215 standard must withstand the impacts of these ice balls of different diameters and at different speeds.

Now, we are increasingly experiencing more extreme weather episodes, and this means that it cannot be ensured that if a larger stone falls, or at a greater speed than that of the pots, the panels could break as happened with the summer hailstorm in La Bisbal.

The most advisable thing is to insure the solar installation, beyond the house's own insurance and insure it against these extreme episodes of wind and/or hail.

Often in the case of disasters of this style, the insurance will not cover if there is a declaration of a disaster zone by the Government. In this case it will be the Insurance Compensation Consortium who will take care of them. However, for this to happen it is necessary to have insurance.

The roofs of the communities are not for the exclusive use of the person who lives on the highest floor, but belong to the community of neighbors, therefore according to the Catalan civil code, you will have to ask the community for permission if you want to put a solar installation for individual use as if it were a community installation.

To request permission, it is necessary to convene the community meeting and state on the agenda that you want to request permission to install solar panels.

At the next meeting, the community board must approve the permit to carry out the solar installation by a simple majority of those present.

The VAT law allows 10% VAT to be applied to renovation and repair works.

A solar photovoltaic installation may be considered a renovation or repair installation if and only if:

• if the recipient of the work is someone who uses the home for private use or a community of homeowners.
• the recipient cannot act as a businessman or professional.
• The construction of the home is completed at least two years in advance.
• The cost of purchasing the materials by the industrialist does not exceed 40% of the final cost of the work.
• For this reason, we always ask for a signed declaration from our clients in order to apply this 10%.

Finally, we can also apply 10% VAT to self-promoters.

In FV as in real life, size is not the most important thing….

The efficiency of a panel is the relationship between power and surface area of the panel, therefore a large 550W panel may be less efficient than a smaller 385W panel if the W/m2 ratio is higher. The panels we work with at SolarTradex have an efficiency between 20.6% and 21.3%, and are within the high efficiency segment.

The more efficient the panel, the more kWp you can install it on a given surface.

If you want much more efficient panels - 1% more - you will have to pay practically double for the panels and it may not be worth it.

The solar panels are joined in chains (or strings) in the same way that inside a solar panel the different solar cells are also joined in 3 or 4 chains which are joined at the top of the panel (currently there there are panels that are joined in the central part).

We can imagine these chains as pipes through which water circulates. If we have a shadow that only affects one cell, it will turn out that it will not circulate (water) through all the cells that are connected in chain within the panel.

And if this panel has 4 chains, then only 75% of the water will reach the top of the panel, and this panel will only pass 75% of the water to the next panel connected in chain and therefore to the end of the chain will only reach 75% of the water and all because of a single cell.

In summary, all shadows are important and therefore it is advisable to minimize them even if they seem small or only affect a part of a single panel.

Performing an installation with microinverters can be a very good option if you have significant shadows in your installation.

Working with microinverters allows the shadows on some panels not to affect the rest of the panels; however, if you don't have shades you will pay a premium for the installation and the installation will work just as well as without microinverters.

If you install microinverters and a microinverter breaks down, you will not lose the totality of the production compared to installing a single inverter, but on the contrary you will have much more chances of an inverter breaking down than if you work with a single inverter.

In addition, if a microinverter is damaged, you will have to climb up to the roof to repair it and remove the corresponding panel, so the cost of repair/replacement will be much higher.

The main difference between both types is the power. EVC's for domestic use have been standardised to a maximum power of 7.4 kW in single-phase and 22 kW in three-phase. In fact, most models have the option of 7.4 kW, 22 kW or 22 kW adaptable to 7.4 kW.

In the case of having a single-phase installation, a single-phase charger must be installed at all costs.

However, single-phase or three-phase EVC's can be installed in a three-phase installation. We must take into account different factors:

Three-phase EVC's can have more power. The car will be charged before, but this energy (contracted power) must be available.

A minimum available power must be guaranteed. In the case of single-phase EVC's it is usually between 1.4 kW and 2.3 kW depending on the car. In the case of three-phase ones, the minimum is between 4.1 kW and 6.9 kW depending on the car.

Finally, the cars are also three-phase or single-phase depending on the model. The limitation comes when a three-phase EVC feeds a single-phase car, then the maximum power will be reduced from 22 kW to 7.4 kW.

The load will be defined by three factors (as long as the EV allows it):

• The power of the charger (single-phase EVC up to 7.4 kW, three-phase EVC up to 22 kW).
• The contracted power in the electricity company
• The available power taking into account the contracted power and the one the house is consuming. For example, if you have a contracted power of 5 kW and are consuming 3 kW, the available power will be 2 kW.

The EVC can be configured to limit the charging power. Now, waiting to have enough energy and limit the EVC because we don't exceed the contracted power can be very annoying. That's why we installed an external meter that communicates with the EVC to automatically manage what power is available and use the maximum up to the limit that is set (automatic load balancing).

One option is to have an available power greater than the set of maximum powers of the existing EVC's in the installation. This option requires that the contracted power be high (if the company allows it) and, therefore, a high maintenance cost.

The second option is to limit the power of each charger to ensure that the available power is not exceeded. This option limits the load on the vehicles and never takes advantage of the maximum power of the EVC's.

The last option is to install an energy meter that communicates with the main EVC and that it automatically manages the total available power between the chargers in operation. In this way, no more energy than necessary should be contracted (if not wanted) and the EVC's will operate at the maximum power available depending on the EVC's that are in use.

There are EVC's that allow it. What they need is to read the current consumption through an external meter (the same as load balancing) and the charger will use the surplus energy necessary so that the reading is neither negative nor positive with the minimum charge limitation and/or maximum that the vehicle has connected, this will minimise solar surpluses. For example, if we have 1.3 kW surplus, the EVC will not be able to put it in the vehicle since they are not enough for it to allow charging.

This mode of operation allows two modes of solar surplus management, one in which it will only inject solar surplus into the vehicle and another that allows a mix of charging with grid energy and solar surplus previously defined by the user.

EVC's for domestic use are configured through the brand's App. The main configuration is done via Bluetooth. The client, owner of the EVC's, will have access to modify its configuration according to its needs.

In addition, most EVC's allow connection through the Internet to manage some parameters. How to program the loads, start and stop the loads or even modify the maximum power of the EVC.

The internet connection is only necessary if you want to change some parameter of the installation, such as starting and stopping charging, scheduling charging times or managing users (giving access to RFID cards, etc.).

One of the great advantages of the EVC is to programme the loads in the EV. Each EVC has its App/platform to manage the timetable.

The first option is to install a EVC connected directly to the house meter (if access exists). The cabling up to it can be individual or it can be collective (community pre-installation) depending on what the community decides.

The second consists of installing a protection subframe from the parking meter from which individual derivations would be made for each EVC.

The most practical way to bill the energy that is spent charging from the community meter is to install an approved meter (MID) in each EVCand, through a platform managed by the community itself, make the necessary bills (for charging session, at the end of the month, etc).

It must be managed through a platform dedicated to this purpose. There are different platforms that allow different configurations; some are for regular users of that charging point (private use) and others are open to anyone registered on the platform (public use). Depending on the platform, it is possible to manage which users have access to it and the rates they have in a personalised way.

The subsidies are very slow to be resolved due to lack of ICAEN resources.

RD477/2021 establishes a period of 6 months to grant the subsidy, although currently this period is far exceeded given that as of today only applications registered on 01/10/22 have been granted.

Once the subsidy is granted, a period of 18 months begins to justify the investment and then the ICAEN has 6 months to pay.

The IBI bonus depends on each municipality, although it normally takes a minimum of 6 months.