Backup Power for mains failure

SP Pro LG genny
What will you do if the mains power fails. It’s happening a lot on the South Coast at present due to flooding.

The options.
Battery and inverter backup - A battery system and associated inverter provides backup power to your home when the mains power fails.
Generator backup - A petrol or diesel generator is used to power your home.
Candles - Who needs power? It’s just like camping.

Most people want backup power to run their essential electrical items such as refrigeration, water pump, lights and electronics.
A backup power supply that can deliver around 3kW of power is a good average system to supply these needs. You might have to manage the run time of some of your appliances but you should not be too inconvenienced. If you need more power than this you’ll need a larger generator or battery system - readily available but more expensive.

The cheapest initial outlay option is to buy a decent petrol generator and have Bunya Solar install the correct control gear to allow you to switch selected house power circuits between mains power and generator power. The switch over can be automatic or manual. With an automatic system the house will switch over to generator once the generator has been plugged in and started. With a manual system the changeover switch must be operated by hand after the generator is plugged in and running. After the cost of a generator you’re probably looking at around $600 for Bunya Solar to install the control gear and generator input. This gives you a legal, safe and easy way to run your house from a generator.

The other option, besides candles, is to install a battery system and a battery inverter. Bunya Solar installs these systems in various configurations and power sizes. Our most common systems include the Selectronic Hybrid battery inverter and a lithium battery or a Fronius GEN24 inverter and lithium battery. These systems will integrate with your exisiting solar power system and as well as providing backup power during mains outages will also move unused solar power from the daytime to the nighttime to maximise your solar usage and limit your consumption of grid power.

Backup power system example cost.

Family home. approx $15000 fully installed and integrated with your exisiting solar system for the Selectronic SP Pro system.
Approx $10600 fully installed and integrated with your exisiting solar system for the Fronius GEN24 system.

When the grid is functioning normally during daylight hours with the sun shining your household loads will be supplied initially from solar power. Any power required in excess of what the solar panels can supply will come from the battery until its SOC drops to 20% After this any excess power will come from the grid.
When the grid is functioning normally during night hours your house power will come firstly from the battery till it’s SOC drops to 20% and then from the grid after that.
The battery and inverter combination can supply up to 3.5kW of power into the house while mains power is active. Any power required above this figure will be drawn from the mains.

During a mains outage your power system will automatically go into stand alone mode and supply power to your house until the battery SOC falls to 15%. The batteries will recharge from solar even if the mains failure extends over many days. Your power usage will then be limited to the stored battery energy overnight and the solar energy during the day. The system should be monitored to make sure that the battery is being recharged during daylight hours to enable it to provide power overnight.

This system will move unused solar power from the daytime to the night time rather than letting it feed back into the grid. If you do not have enough solar power to cover your normal household usage plus some extra to charge the battery system then you should expect some battery charging to come from the mains supply.

Selectronic System includes:
  • Connection of your exisiting grid connect solar system to the battery backup system so that you can live through multiple days of no mains power.
  • 3.5kW Selectronic battery inverter / charger with high surge capabilities. Made in Australia. The bees knees of battery inverters.
  • LG Chem RESU 10 Lithium battery with 8.3kWhrs of usable power at 85% Depth Of Discharge per night. This cyclic DOD will give an approximate service life of 13 years. Battery system can have extra capacity added at a later date if needed.
  • Mains Backup Switchboard connected to select power and light circuits in your house.
  • Full installation and system training for client.

Use our contact page to ask for a more specific quote to suit your needs. It would be handy if you could have an idea of how much power you’re using per day. You can get this information from your electricity bill.