Grid Connect with Battery Backup

EcoSouth has been supplying and installing Grid-battery systems since the year 2000.

This can be a complex area with many different features, and different ways of achieving similar outcomes.

Power Cut Protection

To date, Grid-battery systems (GB) have been installed to provide power during power-cuts. They can provide back-up power for a range of appliances, depending on sizing; eg computers, televisions, and fridges. They are also well-suited for critical business, agricultural and medical equipment.

During the day the backup time is extended by the power from the solar panels, if the system has the 'direct-solar' feature, ie if the equipment installed has the option that allows the panels to charge the batteries.

Whenever power sources are switched (eg from mains to battery-backup) there may be a momentary ‘dip’ in power, which could slightly affect appliances, eg re-boot desktop computers. This is dependent on the capability of the system equipment.

Load-levelling & Load-shifting

Grid Battery systems may also be capable of 'load management' of your house's electricity:

'Load-leveling' - minimises import from grid during the day - that part of any momentary draw above your export, will be drawn from battery instead, which will then be topped up (via solar) when the momentary load has ceased

'Load-shifting' - running appliances from battery for a limited period after sundown. The batteries remain slightly discharged overnight, and recharged the following day from power that would otherwise be exported.

This gives the advantage of maximising the in house use of your solar production, reducing your energy imports and minimising energy exports (which customer now receive less $ value for, compared with their imports)

These are complex and presently costly to implement, and a number of systems are appearing on the market. EcoSouth will offer these once satisfied with the technical/economic viability, support and the forecast lifetime of such systems. These systems may be able to be cost-justified if you have unreliable grid power (frequent power cuts) in your area, as load management systems can also be capable of supplying power during a power cut (dependent on the equipment provided for your solution)
As these are complex systems, tailor made options will generally be the most effective solution. Please do contact us to discuss requirements.

Diagram of Normal Day to Day usage

diagram normal

Diagram of Power in a power-cut

diagram powercut

Grid-Battery Components

This consists of similiar components as a grid-connect system (panels, grid feed inverter, balance of system, SAPN meter) plus some extra components such as

  • Control system to manage power flow (storage and release)
  • Inverter that can operate 'islanded' (ie independent and disconnected from the main grid) to supply power 
  • Battery bank (various technologies dependent on application)
  • Capability of panels to charge batteries in a power-cut

It is possible to install an integrated grid battery system from scratch (most options, best configurability), OR to retro-fit an existing Grid-connect system (restricted options and flexibility).

Grid Battery Inverters

Inverters that are able to run in 'islanded' mode where they are directly powering your appliances are generally more highly stressed than grid-connect only inverters. As the inverter must supply large start-up currents for the appliances, ie fridges etc. As a supplier, we must take great care in the selection of this inverter to ensure that is have a reliable and trouble-free life for both your peace of mind and ours! There are already a large number of (cheap and not-so-cheap) inverters offered on the market that just are not capable of long-term domestic usage, some of which may not meet all Australian standards!


This may be intergrated as part of a grid battery inverter, or a separate external control unit (eg typically for a retro-fit grid battery package). The control-system, depending on its complexity, may manage: when to export, when to reduce export, when to charge, how much power to export after sundown, and even maybe able to automatically switch household loads on and off at suitable times.


In general, we find that most new battery technologies still has a way to go to match existing reliable battery technologies - the proviso being you have the storage space! It is true that Lithium battery technology has the great advantage of being lighter and physically smaller for the same usable capacity, but it presently comes at higher cost. In some situations, it may be the most logical choice.

Storage-time vs economics: The more time you want appliances to run from battery, either in a power-cut, or to export after sun-down, then the larger battery-bank you will need. The unit-cost of the consumable battery-bank must be paid off over the life-time of the system to determine the economic viability.

Beware!: We are seeing systems offered specified with very deep daily depth-of-discharge (DoD) rates. This severely shortens the life of the battery, thus making that rate of battery usage uneconomic, which in turn reduces your overall payback time, and may even cancel-out the economics for installing it in the first place!

Direct-solar capability

This allows the panels to charge batteries in a power-cut. Some systems have this as a native capability, whilst others (say retro-fit systems) may need to have this added as a separate feature. It is possible to have a system that recharges batteries in a controlled manner from mains only - the emphasis of these systems is to achieve load-levelling or load-shifting for economic reasons, and not primarily for length of power availability in a power-cut.

House-wiring changes vs economics

Note that either controlling and/or supplying a small number of appliances in the house, usually requires separate AC power cables to be run. If you are only wanting to back-up your fridge, some lights and a small TV, then you do not want your comparatively small GB system to try to run ALL the house at once in a power-cut! (However, larger systems are possible: allow a budget from around $25k for a small house, with further investment required for larger and more complex systems.)

Please call or email for us to quote a system to suit you on 8371 5655 for indicative pricing for a grid battery system to suit you, whether only for a few appliances, or for many.