House with solar panels
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Solar plus batteries gaining momentum

Attending a packed presentation on solar plus batteries confirmed my suspicion.  People in the suburbs are serious about exploring options for their electricity supply.  Eastern Climate Action Melbourne (ECAM) organised the free event with the support of Whitehorse Council.

Setting the scene.

bhive environmental logo

Rob Gell from bhive environmental started the night by reviewing the recent climate change indicators.  A ripple went through the crowd when he suggested that the Australian government needs to get its act together on sensible policies to address the issue.  I think Rob was saying we don’t need to wait for the government to come on board.  We should take action ourselves.  It didn’t matter if the driving force was being greener or just saving money, people have the necessary technology to reduce the amount of electricity made from fossil fuels.

The presentation was in two parts – the mechanics of solar plus batteries and then the economics.

Solar plus batteries is becoming more common.

Solar plus batteries arrangement

Pat Tale from Enviroshop covered the basics of installing solar cells on the roof and then hooking them up to battery storage.

For people living in the suburbs, he didn’t recommend going off-grid by cutting ties with traditional electricity suppliers.  This costs up to $1500 extra and means putting in a generator for those times when the batteries go flat.  Going off-grid doesn’t always live up to the dream as shown by the experiences of the off-grid guy.

Tesla Powerwall 2

Lithium-ion batteries are the current technology of choice for home batteries.  They fit well with the cycle of charging from the solar panels during the day and discharging to supply the home at night.  Buying a battery from a well-known established supplier like LG Chem, Tesla or Enphase ensures peace of mind if any issues arise after installation.

So, how much do they cost?   A 1kW battery from Enphase costs about $2600. Larger capacity batteries from LG Chem go for about $1500 per kW.  The low price champion is Tesla at $880 per kW.  Installing a 13.5kW Tesla battery costs about $12k.

Add an Energy Management System.

But wait, there’s more!  Pat recommended adding an Energy Management System (EMS) to extract the maximum value from the system through monitoring and control applications.

  • Monitoring gives an overview of the electricity flow around the house – how much is being produced, where it’s being used, etc.  Knowing what’s happening with electricity flows around the house means saving money in all sorts of ways.  Should that old appliance be replaced with something more efficient?  What device is using all that electricity during peak tariff time?
  • Control systems range from the ability to remotely switch devices on/off to fancy programs that “learn” usage patterns so they can make decisions on optimising electricity inputs and outputs.  The more advanced EMS packages allow residents to trade like a power station.  When prices spike on the electricity grid, the EMS exports excess power.

One Step Off the Grid released a summary of the available EMS to help readers compare prices and features.

Extra features can come at a cost.

Like me, Pat is enthusiastic about an EMS supplied by an Australian company called Reposit Power.  This clever system works behind the scenes to continuously optimise the flow of electricity to and from the house.  Low battery level due to a cloudy day?  Reposit predicts the next day’s consumption and automatically tops up the battery using cheaper off-peak electricity from the grid.

Reposit Power is an option for solar plus batteries

Be prepared to pay for EMS features.  For example, Reposit Power EMS will add about $600 to the cost of  solar plus batteries.  The argument is the ability to export electricity at a premium price reduces the payback time for the entire system. Other suppliers like Redback Technologies include an EMS in their equipment.

What are the economics?

The price difference is driving people to consider adding battery storage.  During the day, excess solar power is sold to the grid at at 5 to 10c per kWh.  At night, residents buy it back at 20 to 30c per kWh.  Battery storage means the electricity made during daylight hours is on tap for the home that night (when the peak power tariff kicks in).

Comparing cost of grid electricity with solar plus batteries

Bruce Mountain from CME took us through the latest economic analysis of solar plus batteries.  A lot depends on how active you are with getting the best deal from electricity retailers.  On pure economics, you are better off with the lowest price offers from traditional suppliers.  Of course, this means spending a few hours each week analysing the 500 or so agreements offered by retailers to work out which one is currently the best and then instantly swapping to the new deal.

The economics of solar plus batteries sits between getting a retailer’s discount for paying on-time and just accepting the regular bill with a standard contract.  Rising grid electricity prices mean this will change as shown by the experience in South Australia.  Those residents are already financially better off going to solar plus batteries.

In rough numbers, a household using the average amount of electricity that installs a 5kW solar array and a 10kWh battery should expect an 8 to 12 year payback.  Interesting that Bruce said installing a solar power system already makes good economic sense.  Many people might see this as a sensible first step while they waited for rising electricity prices and falling battery costs to get them across the line.

Messages for us?

Fitting our new homes with solar cells on the roof and a battery pack in the utility room is the way to go.

There are definite environmental benefits and the cost/benefit analysis is steadily improving.


  • Adam

    April 27, 04 2017 11:04:44

    Have you looked into flywheel energy storage systems? They have a great lifetime compared to batteries, some can last for decades without requiring maintenance.

    • Libby & Howard

      April 28, 04 2017 12:27:34

      Hello Adam – I’d heard of flywheel systems but haven’t looked into the possibility of using them as an alternative to batteries. Could you point me in the right direction to get more information on specifications and price?

      • Adam

        April 28, 04 2017 02:39:18

        Looking deeper, it seems the technology hasn’t been scaled down for residential use as much as I had thought.

        There is one company in France targeting smaller, possibly residential, applications:

        This company also has a “smaller” application, but it’s still a 20′ shipping container: . Maybe something that could be shared between a few houses?

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