🇬🇧 – eurosolar Lëtzebuerg a.s.b.l.

Questions around renewable energy

Electricity from the sun: photovoltaics (PV)
Renewable energy
Mobility
Construction
Smart meter
Further questions

Electricity from the sun: photovoltaics (PV)

How much electricity do I produce with my PV system?

Of course, this depends on a number of factors, such as system efficiency, orientation, size of the roof area, shading, etc.

Nevertheless, it can be assumed that in Luxembourg 1kWp (1000Wp) of installed power generates 1000kWh of energy per year (1000kWh/a (a for anno)). To install 1kWp of power, you need about 6m² of available space.

1kWp output = 1000kWh energy/a

Example calculation:

The roof of a single-family house has a total roof area of 100m². The south side (40° roof pitch) can be used with 42m² due to 2 roof windows and thus offers space for a PV system of 7kWp. This produces 7000kWh/a. A family of four has an annual electricity consumption of 4000 kWh without heat pump and electric car, thus producing enough electricity to also supply their heat pump or electric car.

Does a PV system make sense on roofs that face east or west?

In the past, this was not recommended, but purely for economic reasons. Since PV modules are much cheaper today, an east or west orientation makes perfect sense. The advantage of this orientation is that they deliver more electricity in the morning and evening, which is advantageous for prosumer systems.

With flat roofs (10°), the yield is practically the same as with south-facing PV. However, the disadvantage of a flat roof or a flat elevation (flat roof) is soiling. The system must be cleaned once a year.

With steeper roofs, the efficiency decreases. At 30°, for example, you can expect a yield reduction of 12-15%. The use of east and west-facing roofs therefore makes absolute sense for climate protection reasons!

Does my PV system need to be cleaned?

Normally, PV systems with an inclination of more than 25° do not need to be cleaned because there is enough rain in Luxemurg. Even after 20 years, the degree of contamination is so low that the yield only drops by a few percent. Of course, this does not apply in environments where heavy dirt accumulates, such as dust on a farm.

Systems with a slope of less than 25° may need to be cleaned annually or every few years.

PV system insurance

If the system is on the roof of the house, you can ask the insurance company whether the system is insured with the house. If not, you should take out a separate insurance policy. The costs amount to around 100€/year.

Am I allowed to build a PV system in my garden?

In principle, yes.

If the garden is part of the building land, a building permit must be obtained from the mayor (observe distances to neighbours!). If it is to be erected in the green zone, a building permit from the Ministry of the Environment is also required.

However, at the moment you only receive a feed-in tariff and a promotion for systems that are installed on a building.

What are “balcony power plants” and what requirements apply to them?

Balcony power plants consist of one or two solar modules that are connected to a simple household socket (Schuko plug) in the house via an inverter and thus cover part of the basic load of the house. Since these and the associated cables are not designed for high currents, the output of the balcony power plant must not exceed 800W.

Rumours are circulating that balcony power plants are banned in Luxembourg. This is not true. There is no clear regulation, but the grid operators in Luxembourg accept balcony power plants up to 800W (see this source for further informations).

When installing balcony power plants, it is also important to observe the applicable building regulations (possibly ask for a building permit) and to ensure that the mounting is professional and can withstand storms. Especially if there are other balconies or walkways under the system.

Such balcony power plants do not endanger the safety of the residents because the electronics are built in such a way that they only feed in when there is voltage in the flat grid. So if the fuse or the residual current device (RCD) trips and disconnects the flat from the voltage for safety reasons, the solar power plant will also no longer feed in.

Although the balcony power plant feeds in on only one phase, the base load is covered on 3 phases, as so-called balancing meters are used in Luxembourg (explanation under FAQ Smart meter). These calculate the sum of imported and exported power on the 3 phases.

How long do my solar panels effectively produce electricity?

Although the efficiency of solar panels decreases over time, this decrease is not very high at less than 1% per year. Today, there are systems that have been producing electricity for more than 35 years without any problems. So there is no reason not to continue operating old systems that are more than 15 or 20 years old.

However, the yield of the system should be checked regularly. A single panel can always fail. Since PV panels are usually connected in series, a defective panel can greatly reduce the yield. Often, defective old panels can be replaced and the system can remain in operation.

What different PV panels are currently available?

Almost all panels today use monocrystalline cells (80% of all cells in 2020). These have the highest efficiency. In addition to polycrystalline cells (lower efficiency), there are also thin-film cells. These panels are extremely thin and light and can easily be mounted on less stable structures or facades. The efficiency is somewhat lower than that of monocrystalline modules. They are usually made of CIGS (a mixture of copper, indium, gallium and selenium) or CdTe (cadmium telluride – rarely installed on private roofs).

Can I use my own electricity?

Yes. Since the Prosumer Act, this is even expressly desired by the policy. You can find all the information via the following link (only available in french).

What is better: self-consumption or feed-in?

BOTH :).

Self-consumption reduces the transport losses of electricity and relieves the electricity grid. Without batteries, it is possible to consume about 25-45% of the solar electricity yourself. 45% is possible if you own an electric car and charge it whenever there is daylight. With batteries, a self-consumption of solar electricity of 70-80% is possible.

The electricity that is not used by the owner is fed into the grid and paid for.

With a new system, you can receive a subsidised feed-in tariff for 15 years (system must be on a building!). The feed-in tariff for systems under 10kWp is 15.06Cent/kWh in 2022 and only 14.61Cent/kWh in 2023.

Old installations will be remunerated as grey electricity according to the “prix du marché” (also see the question What is the „prix du marché“?).

As electricity prices will rise massively due to the uncertain situation, self-consumption will become financially more favourable.

Can I become autonomous with my power supply?

This is very difficult in Luxembourg and not desirable because of the lack of possibility to use surplus electricity.

As there is not enough solar energy available over 3-4 winter months, this time would have to be bridged with a generator. Since neither sufficient green hydrogen nor e-fuels are available, the generator will use fossil energy and produce electricity with very poor efficiency. In addition, air pollutants and noise are produced.

In addition, too much electricity is always produced in summer. If one is not connected to the grid, other citizens cannot use this green electricity (feed-in) and the output of the PV system is reduced in the stand-alone grid or switched off completely.

Is there enough space for PV in Luxembourg?

YES!

If we succeed in massively reducing energy consumption, 31km² of PV surface could provide half of the energy. In Luxembourg, there is a total area of built-up land of 253km² (source: STATEC), and 1315km², agricultural land. As it will be difficult to accommodate all the installations on the designated buildable area alone in the next 8 years due to many administrative and other hurdles, the agricultural area must also be used (also see www.agripv.lu).

Does the production of PV panels consume more energy than they can supply during service?

NO!

A PV system made of monocrystalline cells has, after about 2 years of service in Luxembourg, produced again the energy that was needed for its manufacture. If renewable energy is used for production, no unnecessary CO2 is produced.

What to do with a PV system when the feed-in tariff has expired?

Since June 2023, it is possible to distribute or sell your electricity overflow via the new platform E-Community (www.e-community.lu).

The other option is to let the system continue to run, as it still works perfectly. PV panels last longer than 30 years and do not lose much yield. When the tariff has expired, you can still use the modules for 15-20 years for your own consumption.

Can the grid operator reduce the output of my PV system?

Yes, for systems over 30kW, but only if this is absolutely necessary to guarantee the stability of the grid.

How much VAT and sales tax do you have to pay for the new installation of a PV system?

If you generate profits of less than 35,000€/year, you do not have to request a VAT identification number, but you may. For small systems under 10kWp, this amount is far from being reached. In this case, the income does not have to be declared in the tax return. For further information please take a look at the Circular dated 22 September 2021 (only available in french).

If you decide to have a VAT identification number, for example to save VAT on the PV system, you must keep it for 10 years and submit a VAT return every year!

I own land in the green zone. Am I allowed to build a PV system there?

Luxembourg has been one of the few countries in the EU over the years where PV systems are only subsidised if they are on buildings.

A PV plant (then without subsidy) can be erected on building land if the mayor grants permission. PV plants in the green zone have never been allowed.

For some years now, the Ministry of Energy has been issuing tenders for large PV plants, but only on roofs of large buildings or on industrial sites.

In the green zone, a positive decision by the environmental administration is required, but unfortunately this is practically impossible under the current Nature Conservation Act.

At the moment, thanks in part to lobbying by Eurosolar, work is being done on a tender for AgriPV systems in the green zone on agricultural land. On the site where an AgriPV system is to be built, agricultural activity must continue. It is not enough to let sheep graze on the land. These tenders are to be published soon.

Renewable energy

What are the renewable energy sources?

There are a total of 5 different renewable energy sources:

• Solar energy Photovoltaics: Semiconductors convert solar radiation into electricity. Solar thermal: Hot water collectors heat water.
• Wind energy Wind power stations: The kinetic energy of the air is converted into electricity by a generator.
• Hydropower Hydroelectric power plants: Turbines that sit in a river or on a dam. The river current moves the turbine wheels and these drive the electricity generators.
• Biomass Biomass power plant: The biogas produced from plant and animal waste is used directly (fed into the gas grid) or indirectly (combustion in an engine that drives a generator or generation of steam to drive turbines that in turn drive a generator).
• Geothermal energy Heat: Geothermal energy can be used directly for heating (Iceland). Heat pump: The heat pump uses the energy stored in the ground to heat the house (reverse principle of the refrigerator). Geothermal power plants: Pumps transport water through deep wells into warm rock. Steam is produced which drives turbines which in turn drive a generator.

How much renewable electrical energy does Luxembourg produce?

Unfortunately, Luxembourg is currently second to last in the EU ranking, ahead of Malta, in terms of the percentage of renewable electrical energy production relative to consumption. And this as one of the richest and most energy-hungry countries in the world!

The first graph shows the percentage of solar and wind energy in relation to the real consumption of electricity in 2022 (6348GWh). If one relates the values to the total energy consumption of over 37000 GWh, one realises that there is still a lot to do!

In its position paper (available in french and german), Eurosolar demands that consumption be reduced to 10000 GWh by 2030 and that no more fossil energy be used. The following graph shows the percentage shares in relation to 10000GWh electricity consumption.

You find the link to the position paper here: https://www.eurosolar.lu/2022/06/22/100-denergies-renouvelables-dici-2030-100-erneuerbare-energien-bis-2030/

Luxembourg’s efforts are still far from sufficient to effectively curb climate change and break its dependence on fossil fuels and nuclear energy.

Which energy provider supplies renewable electricity?

In Luxembourg, all household customers are supplied with renewable electricity. For the most part, this is electricity from old depreciated hydroelectric power plants.

You should choose a supplier whose product also includes electricity from wind energy and photovoltaics. Ideally, the product should also promote the construction of new wind and PV plants through a small surcharge.

Another criterion for choosing an electricity provider can be its overall electricity mix. Does it support coal or nuclear power plants?

On the website www.calculix.lu (available in french, german and luxemburgish) of the ILR (Institut luxembourgeois de régulation) you can compare the different products of the suppliers. On the site you can also see the electricity mix of the different Luxembourg suppliers.

What can I do if I don’t have my own roof but still want to invest in renewable energies?

Since the electricity provider can be freely chosen, you should choose a product from a provider that contains renewable electricity from wind and PV and supports the construction of renewable power plants.

If you cannot install your own photovoltaic system on the roof, for example because you live in a rented flat, you can become a member of an energy cooperative here in Luxembourg and thus make your contribution (see also next question).

What energy cooperatives exist in Luxembourg?

In Luxembourg, there are many energy cooperatives in which you can participate and thus support the construction of new photovoltaic plants.

You can find the list of all cooperatives and their projects on www.biergerpv.lu, (available in french and german) a website we developed and which is constantly updated.

How dangerous are wind turbines for birds?

Birds and bats die from wind turbines. However, studies (only available in german) from Germany show the extent of this bird death. Climate change and pesticides (insect mortality) threaten a dramatically much higher number of birds.

Wind power plants are and will remain indispensable to stop climate change.

To protect birds, large window areas should be covered with stickers of stripes or dots or stray cats should be sterilised (just in german, https://www.nabu.de/ tiere-und-pflanzen/ voegel/helfen/01079.html)!

So there is absolutely no reason not to develop wind turbines, as this is definitely not the most common cause of death in birds, but only a small percentage.

In addition, there are other efforts to protect birds through improved technology. There are already special systems for wind turbines that use cameras and artificial intelligence (AI) to detect wildlife and birds and stop the turbines if there is a threat to birds. (see also this source).

Why is electrical energy (electricity) now used everywhere as a form of energy?

Electrical energy is a noble form of energy because it can be easily converted into almost all other forms of energy. Electricity replaces the other forms of energy, mainly because many devices powered by electricity have a very high efficiency (few losses).

The efficiency of an electric motor today is 98%!! compared to 30-40% for a fossil engine. This means that an electric car requires 3 times less energy than a comparable combustion engine. An electric heat pump can use the geothermal energy of the ground. It requires 4 times less energy than a gas heating system.

Electric energy can be produced relatively easily in a renewable way by using the sun and the wind. In order to produce other energy sources in a renewable way (e-fuels), you first need renewable electricity. During the production process, a large part of the energy is lost. Therefore, it is cheaper to use renewable electricity directly in as many applications as possible.

Why not just use hydrogen?

There is currently very little green hydrogen! Hydrogen does not exist as freely available energy in nature, but must be produced! Today’s hydrogen is mostly produced from fossil energy with many losses and does not benefit the climate. Hydrogen must therefore be produced from renewable energies!

If we produce hydrogen with the help of electricity, about 1/3 losses occur.

Let’s take a passenger car as an example. Since a hydrogen engine has a very poor efficiency, electricity is first generated from the hydrogen and used to run an electric motor. This results in 1/3 losses again. So our hydrogen car uses a maximum of 1/3 of the renewable electricity (30% efficiency)!

A pure electric car charged directly from the PV system, however, can use more than 4/5 (80%) of the renewable electricity.

If we were to rely purely on hydrogen, we would need 3 times more wind turbines and PV installations!!!

But hydrogen is clearly needed to power ships or aircraft, or in industry. And often PV plants and wind turbines produce too much electricity in summer and their output has to be reduced. Instead of reducing the output of the plants, the surplus electricity should be used to produce and store green hydrogen.

Do I need too much or less electricity?

On average, a 4-person household in Germany needs around 4000kWh/year. In Luxembourg, unfortunately, consumption is somewhat higher. With appropriate savings measures, however, this household can easily live with 2000-3000kWh/year. Compare this with your annual electricity invoice :).

Do I need too much or less heating energy and what are the benefits of a heat pump?

A large part of a household’s energy is needed for heating. A normally insulated house from the last century requires around 2000-3000 litres of heating oil or 2000-3000m³ of gas. This corresponds to about 25000kWh electricity/year. If we replace the gas heating with a heat pump, the thermal insulation must be improved, as the flow temperature of the heating water should not exceed 45°C. The best way to heat a house is via a heat pump. The best way to heat is with underfloor or wall heating. However, it also works well with large-area radiators.

This way we can reduce the consumption to 15000kWh. The heat pump can then draw 3-5 shares of the heating energy from the environment and the electricity consumption drops to 3000-4000kWh/year.

How much electricity does an electric car need per year?

Here, too, less is more. Buy an economical electric car, i.e. a car that does not weigh too much. The consumption is between 15kWh/100km (summer) and 20kWh/100km (winter).

In Luxembourg, a car with a 40kWh battery is sufficient. This guarantees a sufficient range (150 km) even in winter. So you can count on 4000kWh for 20000 km/year.

For travelling, you can rent a car or, even better, take the train.

Can I be completely CO2-free with a PV plant?

If we summarise the questions from above, we need, for example, 4000kWh of household electricity, 4000kWh of electricity for heating and 4000kWh of electricity for the car per year. In total, 12000kWh can be provided by a 12kWp solar system (72m² surface). This is therefore achievable for many households. If you do not have the whole area available yourself, you can invest in a community system.

However, this is only the direct energy. Besides direct energy, we also use a lot of indirect energy, which is needed to produce or transport goods. Or energy provided by the state or communities (lighting, heated schools, sports facilities …). Our solar system would have to be 2-4 times larger (depending on consumption patterns) to be CO2 free and to cover the energy of our consumption.

Under the following link you can do a test and calculate how your household compares to Europe and worldwide in terms of energy consumption.

Has electricity consumption increased in Luxembourg?

NO.

Despite other forecasts, energy savings have kept electricity consumption constant at around 6500GWh/a over the last 15 years (source ILR).

Mobility

What is the difference between a charging station and a fast charging station?

E-cars can be charged with alternating voltage (AC) from the normal mains or with direct voltage (DC) at fast charging stations. High-power fast-charging stations charge with DC voltage.

It makes most sense to charge the e-car slowly on the AC grid at home or at work, preferably during the day so that solar energy flows from the grid into the batteries and less buffer storage is needed in the grid.

Since most cars are parked longer than they are driven, sockets or cheap charging stations should be available everywhere so that slow charging becomes the norm. Slow charging protects the grid infrastructure and saves the batteries.

AC charging stations have a power of 2.3-22kW. Fast charging stations have a power of 50-300kW. Not every car can be charged with such high power.

How long does it take to charge your e-car?

Every electric car has a charging cable with which it can be charged at a normal Schuko socket with max. 10A. This corresponds to a power of 2.3kW.

The first electric cars (Nissan Leaf 2011) could only charge on one phase with 16A (3.6kW). Many new cars also only charge on one phase with max. 32A (7.2kW). But more and more cars can also charge three-phase with 16A or 32A (11kW or 22kW).

You can use the following rule of thumb to calculate the approximate charging time for your electric car. You only have to divide the battery capacity of your car by the power of the charging station to get the approximate charging time (of course, no secondary factors, such as the outside temperature, are calculated here)

Example:

Battery capacity of 40kWh / power, charging station of 7.2kW = 5.5hours (further information availabe here in german).

Since an electric car needs around 20kWh/100km, you can simply calculate how long it takes to charge 100km: Time in hours = 20kWh/power (kW).

Here is a small table with the time in minutes:

Charging station power	Charging time for 100km
2,3 kW	8h41
3,6 kW	5h33
7,2 kW	2h47
11 kW	1h49
22 kW	54 min
50 kW	24 min
160 kW	7,5 min
300 kW	4 min

How much does it cost to charge an e-car?

With a current household electricity price in Luxembourg of around 20 cents/kWh and a car with a consumption of 20 kWh/100 km, this is around 4 €/100 km, which is much cheaper than diesel or petrol.

At fast-charging stations, the electricity is much more expensive at 50 to 70Cent/kWh. The costs thus rise to 10-14€/100km.

Can the battery of an e-car be reused/recycled?

Lithium batteries have a life span of more than 10 years under normal use. Often, the batteries are not yet defective, but have only lost 20-30% of their capacity. The capacity may no longer be sufficient for the electric car, but it is still more than sufficient to be used as a buffer storage for renewable energies.

Many car manufacturers are reconditioning the batteries of old e-cars and reselling them as solar storage or using them in interconnected units as larger energy storage units in industry.

Recycling was not an issue until recently because the quantities produced were too small to make recycling financially interesting. This will change massively in the next few years, and it is hoped that the recycling rate will reach more than 90%, as with lead batteries.

Is the electricity grid in Luxembourg prepared for the large number of e-cars that will need to be charged in the future?

Yes, because a power grid is not static, but can be adapted. Our electricity grid will have to be adapted, not only because of e-cars, but also because electricity consumption in general will increase in the coming years. If you want to stay informed about this, you can look at the annual reports of the grid operators (Creos Luxembourg S.A., Ville de Diekirch, Hoffmann Frères S.à.r.l. et Cie S.e.c.s., Ville d’Ettelbruck, Sudstroum S.à.r.l. & Co S.e.c.s.).

By the way, the Netherlands is currently working on a “smart charging” concept. This means that the e-cars will only be charged when the grid is not too busy (e.g. at night) or when a lot of electricity is produced by renewable energies.

In the future, we will see many such concepts around the world. These “smart grids” will not only ensure that sufficient energy is available, but also that the use of electrical energy is made as efficient as possible.

What charging options are there for e-cars?

At home or at work, you can charge your e-car via a normal socket or via a normal charging station (up to 22kW). These are subsidised by the state with up to 50%. If this is not possible, you can charge your car via the Chargy network of currently 300 charging stations. You will find high-capacity fast-charging stations at the major motorway filling stations. Here you can charge your car in under an hour.

How do I get a charging station near my house / flat?

Ask your electrician for a quote. He will advise you. It is usually no problem to install a station up to 11 kW. The charging station only needs to be protected with a fuse and an RCD circuit breaker in the house connection box. If the power of the charging station is more than 7 kW, the station must also be connected to the intelligent electricity meter (smart meter). The grid operator then checks the installation together with the electrician and seals the meter again.

In a new building, it is important to plan empty conduits for the installation of a charging station if it is not installed immediately.

If there are several flats in a building, it becomes more complicated. Here, all parties must agree and a company must take over the supervision of the installation and equitable distribution of the available power. More information can be found here.

Can I go on holiday with an e-car? What do I have to pay attention to?

YES!

Of course you can also go on holiday with an electric car. However, you have to plan well, because unfortunately the network of fast-charging stations does not yet function satisfactorily in various countries.

So you should mark the fast-charging stations on your planned route in advance and determine where you want to take short breaks and which stations you want to use. Online sites such as https://www.lemnet.org/en, apps for mobile phones (Chargemap, Next Plug, Electromaps, Shell Recharge (formerly NewMotion), Chargepoint, etc.) or, in the case of new e-cars, the navigation software of the e-car can help. Currently, more and more Tesla fast charging stations are being opened for non-Tesla vehicles, so that this also offers an interesting possibility in the event of overcrowded charging stations. However, it is important to make sure that your own car also supports this fast-charging option. (see source in german for further informations).

You also need a charging card to activate the station. This must also be suitable for the selected station. Fortunately, there are some cards such as Chargemap or Shell Recharge that cover many stations. The apps of these providers for your mobile phone also tell you whether the station is free and what the price for the kWh is.

How can I make my mobility cheaper and more climate-friendly?

Often, only the fuel costs per km are calculated for cars. However, the price is much higher if you calculate all costs per kilometre. Constructing a vehicle weighing over a tonne (raw materials) to move an average of 1.3 people is overburdening our planet.

For short distances, it is always most effective to use the bicycle (scooter) or to walk. This is not only healthy, but also protects the environment and your wallet. For medium to long distances, the bicycle is also suitable in combination with free public transport.

In addition to trains, buses and trams, there is the option of carpooling, preferably with an e-car. You don’t have to own a car! As with the bicycle, there is the possibility to borrow or rent cars for a short time:

VEL’OH by Ville de Luxembourg (VdL)

Flex Car sharing by CFL

Car sharing by CARLOH

Construction

What is an Energy Performance Certificate?

The energy performance certificate is a certificate on the energy efficiency of buildings. It contains information on the energy efficiency of the building and enables comparison with other buildings. Even without prior technical knowledge, it is therefore possible for anyone to assess the energy quality of a residential building.

The Energy Performance Certificate is mandatory for new buildings, additions and extensions. For existing buildings, the pass is mandatory if the owner or tenant changes. It must be issued by an accredited architectural or engineering office. It is valid for 10 years from the date of issue. Further information on the energy pass:

Energieagence (available in french and german)

Certinergie (just available in german)

Grand-Ducal Regulation on the energy performance of buildings (only available in french)

Is it worthwhile to renovate your house / flat to make it more energy efficient?

With rising energy costs, it is increasingly worthwhile to renovate the home. Often, this also goes hand in hand with increased comfort. Walls and windows are less cold, which increases comfort, and the ventilation system prevents mould. The air in the room is replaced by fresh air every hour, which reduces pollution.

In addition, renovation often increases the value of the house / flat.

How do I proceed with an energy refurbishment?

In any case, a reputable energy consultant should be consulted.

The first thing to do is to bring the house / flat up to the best insulation standard. For example, it makes no sense to install a heat pump in a building that is not sufficiently insulated.

Good insulation requires airtightness. A ventilation system is important to prevent mould growth. This prevents heating costs from being aired out through the window by means of heat recovery.

The next step is to replace the heating system with a heat pump. This can reduce the energy demand by a factor of 3-5!

A further step is then a PV system that can cover one’s own needs.

Why do I need an aeration system and how does it work?

In well-insulated buildings, a ventilation system with heat recovery is obligatory to prevent mould growth. Proper manual ventilation (cross-ventilation several times a day) is time-consuming and cools the room down too much in winter (of course, manual ventilation is possible in summer).

Ventilation systems with heat recovery are not air conditioning systems! Fresh outside air is used which is only heated by the exhaust air (without mixing). The air exchange takes place at a slow speed and with warm air, so that there is no noticeable draught.

Maintenance of the system consists mainly of changing the air filters 3-4 times a year on a regular basis. You can do this yourself if you wish. If the filters are installed correctly, it is not necessary to clean the ventilation pipes.

How do I improve the CO2 balance of my home?

Here is an interesting document on this question from the “Laboratory for Photovoltaics” of uni.lu.

Smart meter

What is a Smart meter?

A smart meter is a so-called intelligent electricity meter that measures the consumption and/or generation of energy. It replaces the old kWh meters in Luxembourg and is called „Smarty”.

The data is transmitted every quarter of an hour via the electricity grid to a central system (operated by Luxmetering) and from there to your grid operator and energy supplier. The meter no longer needs to be read manually.

The meter has two switching relays with which the grid operator can reduce or switch off permanent consumers with high power (e-car charging station, heat pump, boiler) in case the grid is overloaded.

In addition, the meters offer a customer interface, called the P1 interface. In addition to imported (consumption) and exported (PV) energy and power, this provides a lot of additional information such as power, current and voltage per phase, which can be useful for controlling a smart home, every ten seconds. The information is protected from misuse in Luxembourg by encryption. The customer must request his decryption key from the grid operator in order to access the data. Further informations can be found here.

How to use the P1 interface?

Recently, the energy suppliers have been offering a solution with their Smarty+ dongle. This can be used via an app, and the 10 second values can be uploaded to a cloud, where they can then be retrieved in the form of a file. You can find more interesting info on the webpage of the Smarty+.

However, alternative solutions have existed for a long time that can be better used for home automation and do not require an external cloud. However, these require a certain technical knowledge:

The P1 interface is an inverted serial interface (EIA232). There are special cables that invert the signal and convert it to USB so that the information can be processed by a PC or, better, a mini-computer (e.g. Raspberry Pi). Decoding is done by software (e.g. Python) or an add-on for home automation software (openHAB, Homeassistant, ioBroker, fhem, …).

However, you can also send the data to the home automation software via WiFi or LoRaWAN using a simple circuit (resistor against 5V) and a WiFi-capable microcontroller (e.g. ESP), just like with the Smarty+. The MQTT protocol is often used for this.

Further information on this and on encryption can be found here.

What can I do with the smart meter data?

A first step is to reduce consumption. Of course, this is easier if you know it. Due to the high temporal resolution, you can determine exactly when individual devices require energy and thus identify possible power guzzlers.

If you produce solar energy yourself, you want to use it efficiently. With the smart meter data, you can charge your electric car when the sun is shining. Intelligent chargers even make it possible to adjust the charging power to the solar radiation.

You can also use the sun at night with the help of a battery. The smart meter data can help optimise the charging and discharging of the battery.

If you have a large hot water tank with heating resistors, you can store excess solar energy in the boiler.

Will the grid operator cut me off from the electricity with the smart meter?

Energy suppliers in Luxembourg are required by law to perform a public service task. The rights of consumers are also monitored by the regulatory authority. Even if the smart meter makes it possible to reduce the power of the electric car or the heat pump or to switch them off, this will only be effective in an absolute emergency, when the grid is overloaded.

If you charge your electric car slowly and/or use PV and battery storage, you can easily control your system so that the output of 7 kW is not exceeded and the system is not switched off.

What are balancing meters (Smart meter)?

In Luxembourg, balancing meters are used. This means that it is not the power per phase that is considered, but rather the sum of all three phases. Here is a small example:

A solar installation delivers 6 kW on all three phases (L1, L2, L3) during one hour. The exported power is therefore 2 kW per phase. If the electric car is now charged with 4 kW on one phase (L1) during this hour, the Smart Meter provides me with the following values:

act_pwr_imported_p_plus (1.7.0) = 2 kW
act_pwr_exported_p_minus (2.7.0) = 4 kW

If we now look at the energy values of the smart meter, we see that no energy was imported (bought) and effectively 2kWh of energy was sold.

Further questions

What is the difference between a grid operator and an energy supplier?

The grid operator ensures that the energy can reach your home. He lays cables and installs transformers. He owns the smart meter. You can’t change your grid operator! The largest grid operator for private customers in Luxembourg is CREOS.

The grid operator determines the grid usage costs, which amount to around 6 cents/kWh for the electricity price.

The actual energy is then supplied by the energy supplier. A large energy supplier in Luxembourg is ENOVOS. It buys energy on the markets and sells it on to customers.

What does the ILR do?

The mission of the Luxembourg regulatory authority (ILR, Institut Luxembourgeois de Regulation) is defined on its website as follows:

The ILR ensures and supervises, in the interest of consumers, the proper functioning of markets based on effective and sustainable competition and guarantees universal service. It regulates the following economic sectors: electronic communications, electricity, natural gas, postal services, transport and radio frequencies.

The ILR gives consumers the opportunity to raise objections to new regulations and laws through “consultations publiques”. The ILR’s reports on the electricity market (“bilan annuel” and “chiffres clés du marché de l’électricité”) are worth reading. The ILR is also responsible for providing statistical data (just in french).

Eurosolar Lëtzebuerg a.s.b.l. uses this official data for its statements.

What are TCCs?

The TCCs are the Technical Connection Conditions, so to speak the bible of the electrician. The TCCs are drawn up by the network operators and approved by the ILR before they are implemented by the politicians. The TCCs for the low-voltage grid can be found here in german and here in french. Unfortunately, the TCCs are difficult to read and interpret in many places.

How is the price of electricity divided up?

At the moment, about 1/3 are electricity costs, 1/3 are state taxes, among others to support renewable energies, and 1/3 are grid utilisation costs. However, it can be assumed that the share of pure electricity costs will increase in the near future (also see „prix du marché“).

What is the “prix du marché”?

Electricity is marketed on the electricity exchange. The Luxembourg regulatory authority calculates the average value of this „prix du marché“ per month. In recent years, this has been around 3cents/kWh. Since October 2021, however, the electricity price has risen steadily. In the first half of 2022, the averaged value was 18cents/kWh. Since this price increase will have a delayed effect on the electricity price, we will have to pay much higher electricity prices next year, which will make self-consumption more interesting.

Does a citizen energy cooperative need a business license from the Ministère de l’Economie (Classes Moyennes) to sell electricity to the municipality?

No, no business license needs to be requested here. On the other hand, the building concerned must form an AERC (Autoconsommateurs d’énergies renouvelables, agissant de manière collective) with the municipality, similar to a residence (co-ownership).

Through this channel, electricity can be shared with the municipality and no further authorization is required. The AERC must be registered through the CREOS. After that, a tariff can be agreed with the municipality for the sale of electricity.

What kind of aid (subsidies) is available?

Since mid-2022, there is a simulation programme for calculating the climate bonus. This makes it possible to precisely determine the respective subsidies from the ministry. These range from electric cars to new buildings to energy-efficient renovations. There you can also calculate the bonuses in your municipality (if any exist). You can find all the information at the following link.

Current facts on photovoltaics in Germany

For years, the Fraunhofer Institute has maintained a list of questions on photovoltaics.

Here you can read the latest Solarbrief 01.2023 from Solarenergie Förderverein (SFV), only available in German: https://www.sfv.de/solarbrief-01-2023

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