Grid Connect with Battery Backup Power

Self-Consumption vs Energy Exports

With the demise of regulated feed-in tariffs (FIT) we started designing our grid connect solar systems with a focus on "self-consumption". Most electricity providers only offer 5-10 cents per kWh (if anything) while charging their customers 28+ cents for the same kWh. At this exchange rate it is obviously more economical to consume than to export.

Residential consumption usually peaks at 8am and 8pm but due to the nature of the technology, solar production is at its highest between 10am and 2pm.

Oversized Solar Systems

There are already thousands of potentially oversized solar systems in Australia. Habits and energy usage change over time; family members may have taken on day time jobs, started school or left the nest entirely.

Furthermore, solar systems designed under the now closed NSW Solar Bonus Scheme (60 cent per kWh) may have changed ownership resulting in an inferior FIT (and if ownership has changed, did the gross meter get changed to net metering?). The scheme expired at the end of 2016, and left many households with too big a solar system for anyone to profit, but the electricity providers.

Last but not least, some of the more aggressive sales reps may also have omitted that working families do not benefit as much from a grid feed system as no-one would be home during peak production hours. Needless to say, our system designs have always considered individual needs over commercial gains. Have a look at our solar savings calculator that visualises energy usage and production.

Adding Batteries

consuming solar energy on batteries, copyright SMA Solar Technology AG

A grid connect solar system can be taken to a whole new level by adding deep cycle batteries. The cheapest option would be to turn off the export function and charge batteries instead. Such batteries can be much smaller than those used in stand-alone solar systems as the convenience of the electricity grid remains at your disposal. The batteries serve two purposes:

  1. Increase self-consumption
  2. Provide backup during grid failure


Wouldn't it be nice to have solar energy available around the clock – even after sunset? This is now possible with SMA Sunny Island systems.

A Sunny Island inverter automatically charges the connected batteries. When your solar panels produce more power than is required by the household, the Sunny Island inverter will charge the batteries. In the evening (or during cloudy periods), electricity is drawn from the batteries hence maximising self-consumption. The grid will only be ever used as "top up" or last resort.

Backup Power

During a blackout a grid feed system disconnects from the grid - not producing any electricity either for the grid or for the supply of your house. The self-consumption upgrade as described above (zero export system) will supply the house until a custom set threshold is reached, and then shut off.

Solar Export and Batteries

If you want to continue feeding excess power into the grid (e.g. after the batteries are full), more electronics are needed to prevent draining the batteries. This configuration is only recommended for customers with massive amounts of excess solar power or generous feed-in tariffs. Furthermore, grid feeding hybrid solar systems would also require an additional changeover switch to power the house during blackouts.

Upgrade your Grid Connect System

Most existing grid connect systems with an SMA inverter (e.g. Sunny Boy) are "battery ready" making the retrofitting of a SMA Sunny Island system seamless. The newer generation of SMA inverters allows for battery charging AND grid export (in case of excess). Older SMA inverters can still be used for battery backup and/or increased self-consumption (without grid export).

Sunny Island 3.0

Sunny Island 3.0

    Self-Consumption / Battery Backup Upgrade

    This 48V battery system with maintenance free batteries will provide a significant part of your night time energy needs (~5.1kW/h).

    If you have an SMA based grid connect (grid-feed) solar systems this upgrade kit is all you need to increase self-consumption and is the next step in weaning yourself from the big energy retailers. The system can also power your house during a blackout.

    The upgrade kit includes a Sunny Island 3.0 Inverter/Charger with remote control unit, a 48V lithium ion battery pack, all cables and required signage as well as installation (in Northern Rivers). Recommended for existing grid-feed systems from 3.5kW of solar panels. Note: the system will stop exporting excess solar.

    Price: $16,490 installed*

    house wired with batteries - copyright SMA Solar Technologies AG

    Battery Backup + Grid Feed Solar

    The self-consumption / battery backup upgrade is ultimately an off-grid system with grid backup. If you want to still feed excess electricity into the grid you will also need the Sunny Home Manager. The Home Manager requires a web connection, extra configuration and a few accessories. Furthermore, a changeover switch is highly recommended to go with the Home Manager (to power the house during blackouts). Additional wiring may be required depending on your circumstances.

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    *Conditions: Installation site within 50km of Nimbin; single phase power; undercover area for batteries and inverter/charger near existing inverter; SMA inverter with frequency-dependent active power limitation capability.