5 Reasons to choose SMAs Fuel Save Solution

Fuel Save Controller (left) and Data Acquisition Module (right)

Putting solar power into diesel based grids is easy but maximizing the share of solar is a real challenge. To save on diesel consumption, diesel has to be substituted by other energy sources. Solar energy is a cheap energy source but without intelligent system control it is hard to reach high solar shares in diesel grids. Uncontrolled solar energy feeding into a diesel grid can, even with a small share of solar, lower the diesel workload to a disadvantageous level in solar peak times causing inefficient operation of the diesel gensets, more frequent maintenance cycles and damage to the equipment. If too much solar generation capacity is installed, even reverse power into the generator is possible, which can cause a blackout in the best case scenario and equipment destruction in the worst case.

This article shows how the SMA Fuel Save Controller 2.0 (FSC-20) facilitates high solar shares in diesel based micro-grids and thereby saves diesel as well as money in a smart, flexible, safe and easy way with SMA supporting you whenever you need it.



FSC-20 controlling Solar and Battery to safely bring gensets down to 30% genset loading

Example of the FSC-20 controlling the solar and battery power to safely bring gensets down to 30% genset loading

The FSC-20 enables high shares of solar by controlling the solar inverter and battery storage power output in a way that solar shares of up to 90% of the load can be reached without negatively affecting grid stability or equipment health.

On the right is an example of an island power grid where FSC-20 lowers genset production as far as possible. For this system, it is 30% of the gensets nominal power. If more solar power is still available, it is then charged into a battery storage to shift it to the evening hours. And if even more solar power is at hand, it is curtailed by the FSC-20 to ensure stable system operation.

Even more, the FSC-20 can use solar inverters and battery storage to provide reactive power – during the day as well as at night – to keep the grid stable and to optimize genset efficiency.



The FSC-20 optimizes power flows within the grid. While optimization works to achieve the highest possible solar share, the FSC-20 puts grid stability first. The FSC-20 knows about limitations and constraints within the System so it is always able to operate the system safely and with a maximum of cost saving.

In as early as the development stage, all functions are extensively tested in system simulations. Each software release is tested under real-life conditions on SMAs hybrid power systems test facility which allows for testing under real power flows of up to 5MW.

In addition to continuous simulations and tests, the FSC-20 has proven safe operation in more than 120 sites worldwide.



Fuel Save Controller System Layout

Fuel Save Solution system layout

The FSC-20 is incredibly flexible in how it measures the system’s power sources such as solar, generators and loads – flexible in terms of the number of measurement points as well as flexible in terms of the measurement location due to remote measurement units (data acquisition boxes) that may be located in a distance of up to 20 kilometers. When measurement is not applicable or too expensive, the FSC-20 can calculate points in the grid deriving from known measurements. In this way the FSC-20 can be easily integrated into nearly all diesel based grids out of the box. It is able to integrate photovoltaics of nearly any size and is also able to integrate battery storage into the diesel grid to reduce the spinning reserve and to shift energy.


Easy to Use
Fuel Save Controller Graphical User Interface

Fuel Save Controller Graphical User Interface

While the control functions within the FSC-20 are complex and weather as well as loads can change grid conditions within seconds, the FSC-20 is exceptionally easy to operate as it, once set up, operates on its own.

A web-based graphical user interface can be used to set up the FSC-20 and to view the grid status and energy flows. Details can be examined down to each individual device in the system. Live display of the energy flows helps optimize the system and provides insight into the inner workings of the system.

The FSC-20 provides a modbus interface to integrate the itself as well as the complete solar and battery subsystem into any SCADA solution. The available data points range from aggregated site values representing the overall system view and again down to data points for each individual system device.

For long term system surveillance, the FSC-20 records system power values and detects warnings and errors in logfiles that can be downloaded from an integrated FTP server.

Equipped with these easy yet powerful possibilities for monitoring and interaction, it’s easy to add the FSC-20 to any existing system management solution.


Great Sales Support, Training and Service
SMA Solar Academy

SMA Solar Academy

With subsidiaries in 20 countries, SMA has experienced hybrid system designers and commissioning engineers all over the world. This makes it easy to find a perfect hybrid design for your grid and to get it up and running quickly and seamlessly.

Once the Fuel Save Solution is in operation, an experienced service team helps whenever there are issues on site. The FSC-20 offers the possibility of a permanent VPN connection to SMA Service, so if any problems occur, we can provide lightning fast support helping to minimize outages.

To ease installation, set up and operation, the SMA Solar Academy offers training courses for commissioning engineers as well as system operators. With these trainings, your employees gain the theoretical background in how to design a Fuel Save Solution and to understand the functions. They will also learn how to handle the Fuel Save Solution in daily operation. The practical parts of the training take place at SMAs hybrid power systems test facility.


More information

You can find all of our blog posts on the Fuel Save Solution here. It is a great source of information if you are interested in saving fuel or planning to integrate solar energy into your grid.

Do you have comments or questions? Great! Just use the comment field below. We look forward to receiving your comments and we will answer each question as best as we can.

You can find even more details on the Fuel Save Solution Product Website.

If you would like our experts to help you lay out your own Fuel Save Solution, justsend us an email at FuelSaveSolution@sma.de

4/5 - (3 votes)
  1. mohamed hanine
    mohamed hanine says:

    I have a project with a capacity of _800KWC isolated from the network 0 Can the SMA FEUL SAVE system operate without batteries 0

  2. Mohammed
    Mohammed says:

    what is the difference between SMA Fuel Save Controller and SMA Hybrid Controller? what application they used it?

  3. Marc
    Marc says:

    Hi! we currently have a 108 kWp system using 18 SMA Sunny Boy 5.0 and we also have a 150kVA Diesel generator. Whenever there is a power outage, we are soley dependent on our 150kVA genset. since there is no grid power, our solar PV system does not function. will it be possible for us to use the genset along with the solar by adding the Fuel Save Controller to our existing system? I’d really appreciate if I can get come info on this. thanks

    • SMA Solar
      SMA Solar says:

      Hello Marc,

      unfortunately we can’t give you an answer without knowing all the details of your system. It’s best to contact the installer directly or contact our colleagues via Online Service Center. They’ll be glad to help.

      Sunny regards!

  4. Amer Maroun
    Amer Maroun says:

    I am Amer Maroun, an electrical engineer. I have question regarding the communication between SMA fuel save controller and WoodWard easygen-2500-5. Actually, in SMA manuals, fuel save controller can communicates with easygen 3000. Does Anyone try it with the easygen-2500 controller whether it’s a TCP/IP modbus or CAN bus.
    Thanks in advance.

    Amer Maroun

    • Christiane Keim
      Christiane Keim says:

      Hello Amer,

      Sorry for the delay in getting back to you.
      Please contact our SMA Service for technical support, using our SMA Online Service Center.
      We need some more technical information in your case.

      Thanks for your support.

      Sunny regards

  5. Ngoli Nyirenda
    Ngoli Nyirenda says:

    I wish to.k.is of the FSC-20 system is still available from Southern AfricN distributors and of I would need a DC-DC Converter for a system using 4 x TriPower 60s and a 410KVA diesel genset with a nominal load (pumps) of 320W. Thank you.

  6. jayesh Vekaria
    jayesh Vekaria says:

    We planning to have smaller gensets of 550kva for our fuel save controller. We would like to know if we would need a synchronization panel for the generators or would Fuel save controller be able to manage the synchronization. Generator panel would be Cummins Power command. Please let is know your feedback so we could plan accordingly.

    JAYESH says:

    Hi Anke

    Thanks for you feedback

    We have 34 stp 25000 and only 25 inverter are connected to cluster controller. We had to use cluster controller for the meteorological data to show up on FSC interface.

    We would like to have all 34 inverters to be connected so we could monitor the system using sunny portal.

    There is a option for using cluster controller which can handle 75 device, but have seen no more support is available and SMA have stopped this product. There is a second option for SMA data manager but it’s compatibility with FSC( on meteorological data) is what we are consern about.

    We prefer option with SMA data manager

    What would be best available option

    JAYESH says:


    We do have a hybrid system which uses FSC. There is a cluster controller connected to the FSC for weather data. The cluster controller we have can take upto a Mac of 25 devices. We would like to know if we could connect to Home manager to get the weather station data on FSC ?


    • Anke Baars
      Anke Baars says:

      Hi Jayesh,
      Thanks for your request.
      I´m not sure if I got you right, because the Sunny Home Manager can neither handle a weather station nor can you connect 25 devices. Additionally it is not possible to have more master controller in the plant.
      Do you mean SMA Data Manager M? Maybe it would be best to contact your local installer or sign in on our Online Service Center.
      Kind regards,

  9. Julio Garcia Garay
    Julio Garcia Garay says:

    Estimado Sr. Christian Höhle
    Como parte de los trabajos de diploma que se discuten año tras año en la Facultad de Ingeniería Eléctrica de la Universidad de Oriente, Santiago de Cuba, Cuba; en uno de nuestros trabajos hemos escogido la variante de utilizar el controlador de ahorro de combustible SMA 2.0 (FSC-20) que como ustedes ya nos han informado, facilita las acciones de alta energía solar en micro-redes basadas en diésel y, por lo tanto, ahorra diésel y dinero de una manera inteligente, flexible, segura y fácil con SMA, esta variante la utilizamos para un edificio administrativo que cuenta con conexión a red y un grupo electrógeno diésel de la marca Denyo, con 60 kVA de potencia isonorisado; se ha ejecutado un proceso de mudanza al edificio de varias oficinas del territorio y eso ha permitido el aumento de la demanda; por lo que hemos sugerido incorporar un sistema fotovoltaico ligado a red con la variante de utilizar el controlador de ahorro de combustible SMA 2.0 (FSC-20) que permita utilizar el grupo electrógeno solo en momentos de ausencia de suministro por la red y dando prioridad al suministro del sisterma FV. Toda la gestión en ambos modos de trabajo y la contabilización de la energía se realizará por el CAC, así como el monitoreo de los parámetros de la carga, el sistema fotovoltaico, el generador diésel y la red, logrando el mínimo consumo de combustible posible y de energía proveniente del SEN y la estabilización de los parámetros que llegan a la carga, todo en tiempo real y detectando las fallas en los distintos niveles del sistema.
    Se obtuvieron los resultados siguientes:
    2. El sistema que se propone está compuesto por un generador de 516 módulos DSM-250 de fabricación cubana, con una potencia pico de 129 kWp quedando distribuidos en 18 mesas de 25 módulos cada una en el área 1 y 6 mesas de 11 módulos cada una en el área 2 con estructura de soporte SFS-FR-02 que emplea balastros para no perforar la azotea; 5 inversores Sunny Tripower 25000TL, 4 con dos string por entrada de 25 módulos y 1 con 2 string de 25 módulos en una entrada y 2 string de 22 módulos en la otra; cables de 4 calibres diferentes para los diferentes tramos de circuito y dispositivos desconectivos necesarios para las protecciones del sistema fotovoltaico, todo gestionado y monitorizado con el módulo CAC para el trabajo en modo de conexión a red e Isla, determinando el nivel de penetración del recurso solar en dependencia de la demanda de la carga y del orden de prioridad establecido para ambos modos de trabajo, garantizando la estabilidad del suministro de energía a la carga y la detección de fallas del sistema.
    3. Se ha establecido una carga prioritaria de 96 kW para el modo de funcionamiento en modo isla, garantizando que el generador diésel pueda trabajar por más tiempo a tanque lleno de combustible.
    4. El sistema propuesto, generando 172 MWh de energía al año, representa el 79.6% de la demanda de la carga, permite ahorrar 51 toneladas de combustible en su primer año de trabajo, ahorrando 15286 CUC al precio actual de cotización de crudo al país por concepto de energía dejada de producir en termoeléctricas, lo que implica ahorrar 1151 toneladas de combustible fósiles en los 25 años de vida del proyecto. Esto además se traduce en 3 230 683,62 toneladas de gases contaminantes dejados de emitir a la atmósfera durante la vida útil del sistema, de los que 925.7 T son de CO2.
    5. La realización del proyecto resulta rentable desde el punto de vista económico pues, aunque implica una inversión inicial de alrededor de 146 569 CUC, la inversión se amortiza en 4 años y por concepto de facturación la empresa se ahorra más de 1 millón de pesos (CUP) en los 25 años de vida útil del proyecto. Lo que va a permitir la ampliación del sistema y la incorporación de baterías si es necesario en el futuro.

    Necesitamos criterios al respecto y estamos en plena disposición para el intercambio.

    • Anke Baars
      Anke Baars says:

      Hi Julio,
      Thank you for your request. I forwarded it to my colleague, who will contact you.
      Kind regards,

  10. Mohamed Ashraf Karadan
    Mohamed Ashraf Karadan says:

    Dear Mr Christian Höhle

    Can we connect any gunset communication interface? What will be the maximum number of generation can control sma FSC?

  11. jayesh vekaria
    jayesh vekaria says:

    Dear Mr Christian Höhle

    We have fuel save controller (Sr:1901100058)for 991.9 Kw plant at Kaysalt in Kenya. We would like a FTP dump from your FSC to our local FTP server. Would it be possible to have a dump of major parameters like voltage and current for all the three (Pv plant/Grid/Genset)?


    • Christian Höhle
      Christian Höhle says:

      Dear Jayesh,

      currently the logfiles you can download via FTP just contain power.

      We are working on an extended logging function that will – just like the configurable SCADA interface – provide means to specify which values of which device should be logged. It is scheduled to be contained in Release 8 (Software 2.08) by the end of this year. With being able to configure what is logged, you could even log PV as a whole and each inverter additionally in the same file. Furthermore, if you would employ more than one generator, you could also add each generator seperately.

      I hope this answers your question. If you need more information, please let me know.

      Sunny regards,

      • jayesh vekaria
        jayesh vekaria says:

        Thanks you for your response

        Would FCS be able to log power for all the three Sources ? And if yes, Would it also be log data at night when the Pv does not produce?

        If this is possible, what are the steps do we need to take to have this done?

        Please advice


      • Christian Höhle
        Christian Höhle says:

        Dear Jayesh,

        the Fuel Save Controller logs the following values in a 10s resolution:

        – Generator power (active / reactive)
        – Generator reserve power setpoint (for genset controllers that support this: currently Woodward Easygen 3000 series and ComAp InteliGen / InteliSys NTC with hybrid firmware)
        – Solar power (active / reactive)
        – Solar power available (uncurtailed possible power if meteo device attached)
        – Solar power setpoint (active / reactive)
        – Grid power (active / reactive)
        – Grid Frequency
        – Grid line to line voltage
        – Battery power (active / reactive)
        – Battery power setpoint (active / reactive)
        – Load power (active / reactive)

        These data is also collected at night. You can easily use an ftp client of your choice, log in as “User” (careful: case sensitive) with your selected password and download the logfiles from folder /cfc0/fsc/log/DataFast.

        You can then easily open the logs that are stored in csv format for example in MS Excel.
        With a little excel magic, you can easily use it for graphical evaluation of the plant’s performance:
        Diagram from FSC logfile

        I hope this answers your question. Let me know if further questions come up.

        Sunny regards,

      • Kamal Hossaine
        Kamal Hossaine says:

        A Roof top solar power plant with a capacity of 4.5 MWp and 3 Genset 1.5 Mw each capacity running fuel natural gas. For this project we have considered 33 nis 110 KW capacity SMA inverter. please sugest which fuel save controller would bevbetter fir this peoject.

  12. Ammar
    Ammar says:

    Dear Mr. Christian,
    Thank you very much for the article.
    I have some questions and I will be very grateful if you can help me..
    1- Is it possible to use the fuel save controller for PV size below than 30 kWp? And what is the rough guess price for it?
    2- What is the minimum number of genset that I can connect it to the FSC ( is it possible to use ONE diesel generator?)

    Thank you in advance and I appreciate your cooperation with me.

    Best regards,

    • Christian Höhle
      Christian Höhle says:

      Dear Ammar,

      technically it is possible to use the Fuel Save Controller with a PV size below 30kWp and with one generator.
      At the moment, our smallest FSC is the S-Model which is available at 6000 €.

      Sunny regards,

  13. Cele nwaokobia
    Cele nwaokobia says:

    Do you have representatives in Nigeria? Power cut in Nigeria is endemic. Your services will be invaluable here.


  14. Başar Onur Mesci
    Başar Onur Mesci says:

    Dear Christian thank you very much for the article.
    We installed a SMA Zero Export system at Formula 1 Istanbul in 2016. The installed capacity is 40 kwe.
    Is it possible to entegrate SMA Fuel Safe with SMA Cluster Controller and SMA Energy Meter?

    Thank you in advance.

    Başar Onur Mesci

    • Christian Höhle
      Christian Höhle says:

      Hi Başar,

      the Fuel Save Controller can not be used together with a cluster controller to control the solar plant, as the systems would compete for the control of the system.

      But the Fuel Save Controller can take over control. The cluster controller then has to be configured not to control the solar inverters. It still can be used to upload the plants data to Sunny Portal if needed.

      The energy meter is a bit too slow for fuel save controller operation. You would use the measurement system included in the FSC-20 and connect it to loads and generator.

      The FSC-20 can be configured to zero export so that grid requirements are met.

      So you could change the system to a Fuel Save Solution, but it would require some wiring to be done.

      Sunny regards,

      • Basar Onur Mesci
        Basar Onur Mesci says:

        Dear Christian, thank you very much for your prompt and clear response.

        We are looking forward to install the new SMA Fuel Save Controller in our forthcoming projects, especially in Island Systems.

        Thank you very much again.

        Sunny and windy regards,
        B.O. Mesci

  15. mansour alramlawi
    mansour alramlawi says:

    Dear Mr.Christian Höhle,

    I have a factory in Palestine, Gaza city. we have the problem of unstable power supply from the public grid. Now we are thinking to install PV-diesel generator system from SMA to over come this problem. This the basic information I have

    Area size: up to 50 Kwp solar panels.
    Installed generator capacity: 120 Kva
    Max. Load: 110 Kva.
    Daily blackout period:10 hours.

    What is your recommendation, for this project?

    Your fast Response is highly appreciated,

    Best Regards

    • Christian Höhle
      Christian Höhle says:

      Dear Mansour,

      wow – 10h per day of blackout is really severe. Of course, a genset combined with solar power would help a lot.

      Concerning your project, our Fuel Save Solution is built exactly for this situation.
      In case of a blackout, an automatic transfer switch would disconnect the outer grid and the backup generator could start and provide a grid in which the solar system feeds in. The challenge with and adding solar to a genset-based grid is to prevent solar energy from being pushed into the generator – this is one of the most important jobs of the FSC-20. It controls the solar inverters power production to guarantee a safe system operation.

      In case of the external grid returns, the automatic transfer switch connects the external grid. This is detected by the FSC-20 and depending on the grid regulations, the FSC-20 reduces solar production if feedin limits apply or feeds excess power into the external grid. You have to clarify the general conditions with your grid utility.

      So technically this would definitely work.
      I noticed your email as well. We will get in contact with you to clarify the details for an offer.

      We have a design tool called “Sunny Design” that is able to design Solar-Diesel-Hybrid-Plants as well. If you like, give it a try. You can find a short howto here.

      Sunny regards,

  16. Vincent
    Vincent says:

    Hi Christian,
    We have a PV project 50kWp use 2pcs STP 25000 tl-30 in building’s rooftop.
    The genset is larger capacity than this PV system. But when grid is lost, after that the genset start up.
    Can The STP 25000 tl-30 synchronize with genset to feed power load?
    In this case FSC-20 can control these devices. How I can connect this this system?
    Should we need more device?

    Many thanks.

    Best regards,

    • Christian Höhle
      Christian Höhle says:

      Hi Vincent,

      Yes, just like the inverters can feed into the external grid, they can also feed into a Genset grid as long as the grid quality is sufficient (frequency and voltage do not leave the limits set for your grid).

      The FSC-20 can control these inverters. You would use the FSC-20 and connect the measurement of voltage (direct connection) and current (via current transformer) on your genset and load. The connection to the inverters is via Ethernet. The FSC-20 then can control the solar inverters to maximize solar share but keeping the genset under safe conditions.

      Sunny regards,

    • Christian Höhle
      Christian Höhle says:

      Hi Thinus,

      the pricing depends on the needs for your project as there are different variants of the FSC-20 that address different complexities.

      As a rough guess, the Fuel Save Controller Price for systems with a PV size between 500kWp and 1MWp is €10 to €20 per kWp additional to the PV system costs.

      For full information and a pricing indication, please just send a description of your project to FuelSaveSolution@sma.de so that my colleagues can suggest a setup for your project.

      Sunny regards,

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