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

    • 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,

  1. 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,

  2. 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,

  3. 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 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

  4. Cele nwaokobia says:

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


  5. 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,

  6. 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 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,

  7. 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?


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