SonnenFlat-Virtual Power Plant: How Does It Work?


SonnenFlat is a virtual power plant concept that German battery manufacturer Sonnen and Australian home energy solutions Natural Solar launched for the purpose of creating an energy sharing network for those with solar PV systems and Sonnen batteries. It allows those within the network an annual usage allowance at a flat rate fee, whether their solar system is producing the energy or not.

SonnenFlat has now expanded its packages to Victoria, after first taking off in 2017 to a few selected states. After the addition of Victoria, SonnenFlat is now available in NSW, QLD (Energex region), SA, ACT, TAS and VIC.

How Does It Work?

By signing up to the SonnenFlat network your battery becomes part of a Virtual Power Plant in which Sonnen controls. The network works as an exchange of energy between all customers within the network, who are charge a monthly flat rate. A household within the network can pull energy from any three of the following when requiring energy; solar power system, stored energy in battery or the grid. Which one of these three sources won’t matter or effect the flat rate fee, if the energy consumption is within the annual energy allowance that the household has signed up to.

Being part of the SonnenFlat community allows a household to use as much energy as the energy usage allowance allows based on 3 pricing structures and be charged a monthly flat fee instead of a fluctuating rate from energy retailers and the grid. This enables a household to continue to run as normal at night or in a solar systems low performing months without worrying that power bills will spike.


To be eligible to sign up to the SonnenFlat network the household is required to be located within NSW, QLD (Energex region), SA, ACT, TAS or VIC and have the following minimum system requirements;

  • 5kw Solar System
  • 8kwh Sonnen Battery
  • A smart meter (if you don’t have a smart meter Sonnen can install one for a fee)

JUNE OFFERING! – If you have a solar system but do not have a Sonnen battery, Sonnen are offering a SonnenFlat Energy Bundle deal where customers signing up for SonnenFlat in June 2019 can claim $1,000 off their new battery purchase. This is a great option for those who were already looking to add battery storage to their current system.

Available Packages

SonnenFlat offers 3 different packages that you can choose from based on your yearly energy needs and the size system and battery you have installed.


Most Australian households would find the $42 monthly flat fee, economy plan with 7,500kWh energy allowance sufficient. However if you do sign with this plan and find you require more energy you still have the ability to pull from the grid at an additional cost. If this occurs Sonnen makes the guarantee that the excess energy from the grid will be charged at a highly competitive flat rate in comparison to other energy retailers.

There is also the option to select the larger energy allowance plans if you find your energy consumption is much higher than the economy plan.

The best way to determine which plan would be suitable is by reviewing your energy consumption over the past 12 months and choose a plan based on those figures. Sonnen will recommend a plan to you based on what they believe is suitable for your household also.

SonnenFlat Review

According to Sonnen the network has helped homeowners gain greater energy independence for their investment in rooftop solar and sonnenBatteries with no changes to their grid supply.

SonnenFlat customer, Bo Gacic from Coromandel Valley, South Australia said,

“sonnenFlat has protected us from rising retail energy prices since September 2018. We used to pay about $5,600 each year for a household of five to our energy retailer even with our rooftop solar. Our bills are now $42 per month and nothing has changed about the way we’re being supplied electricity. The only change is we get a fixed monthly energy bill from sonnen.”

For those already with Sonnen batteries or looking to install battery storage soon, the sonnenflat network can be a great option to maximise the use of your system and battery. However if battery storage is not something you were considering to install in the near future or your solar system is not larger enough to meet eligibility requirements, then upgrading to just become part of the network may not be beneficial to your savings. Ultimately it is best to analyse your energy consumption and compare the packages available to see if you may benefit from joining the network.

If you’re considering battery storage or want to learn more about battery storage you can do so on our About Battery pages.

Alternatively if you’re ready to add battery storage, install solar or upgrade your system you can get started by requesting quotes!

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Understanding Batteries

Off-Grid Systems

For some households a battery system can be of great benefit and minimise a home’s reliance on the grid. However, it’s important to understand for a battery to be useful your solar system needs to be generating excess energy for the battery to store, which you can then use at night or when the sun is not out.

When selecting a battery, you’ll want to invest in a system that is most suited to your home and can drive the best return on investment (ROI). Despite a larger upfront cost, a higher quality battery may significantly increase your ROI.

    Battery systems start from $6,000 and costs can vary greatly based on the following factors:

  1. Cycle Life-Time

    The number of times a battery can fully charge and discharge.

  2. Battery Power (kW)

    How fast it can be charged or discharged.

  3. Storage Capacity (kWh)

    The maximum amount of energy a battery system can store.

  4. Battery Management System (BMS)

    An electronic ‘smart’ system that gathers data and manages the battery ensuring it does not overload or operate outside of its safe functioning zone..

  5. Inverter

    Battery systems require their own inverter if your solar system does not have a hybrid inverter.

  6. 'All-In-One Unit’

    A system which includes the battery, BMS and an inverter all in one unit.

  7. Warranty

    Length of time or cycles the battery system is under guarantee.

  8. Blackout Protection/Backup

    It’s important to note this is not a common feature of a battery system and could cost thousands of dollars to include. Blackout protection not only requires additional components but also a specialised installation and rewiring. For grid-connected homes, the cost for blackout protection can outweigh the benefit.

Additionally, if your purpose for adding battery is to go Off-Grid and become completely independent from the grid you will need to ensure your solar system can generate enough energy to power your home and your battery system is large enough to store this energy. For homes in metro areas going Off-grid is not cost effective and is only recommended for those in remote areas with limited access to the grid. Off-grid solar systems with battery start at approximately $30,000.

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