Mirvac, Evergen’s smart home saves money, the grid

The first thing the monitoring system in Lisa Zimmerman’s energy-smart house does if the battery is filled early on a hot day is to check if the hot water needs firing up or the air conditioning can be turned on ahead of the afternoon peak.

But if nothing more needs to be done around the house, it discharges the surplus from the solar panels into the grid, earning some income to offset the power bill and reducing carbon emissions from the grid at the same time.

“It’ll do that in the evening as well in the peak times, if it knows we are not going to need a full battery overnight,” Zimmerman, a financial planner, tells The Australian Financial Review

She and her husband Rob, a policeman, Cameron, 16, and Alyssa, 14, are living in the house in Cheltenham in Melbourne’s south-east rent-and-bills free for a year, as part of a trial by home builder Mirvac Group and solar-battery software company Evergen to see if they can produce a mass market “no bills” energy-smart house. 

Australian Energy Market Operator  CEO Audrey Zibelman says the agency is working to avoid the need to curtail solar ...
Australian Energy Market Operator CEO Audrey Zibelman says the agency is working to avoid the need to curtail solar exports to the grid.

Ben Rushton

While the Zimmermans are enjoying the benefit of software that uses weather forecasts and sensor-enabled blinds to optimise their usage of solar, battery and grid power and lower their bills, the trial addresses a wider problem. 


When thousands of such households and businesses are combined, surplus power from their solar panels, batteries, electric vehicle chargers and smart appliances can be marshalled at times of high demand to help stabilise the grid.

Threat is opportunity

As the rooftop solar boom adds the equivalent capacity of a large power station to the grid each year, the drive to smarten up the grid and marshall distributed energy resources aims to turn a threat to grid stability from daytime solar power surges into a weapon to secure it. 

Australian Energy Market Operator chief executive Audrey Zibelman and Energy Networks Association chief Andrew Dillon warned last week that solar power exports may have to be curtailed in areas of highest penetration – something that already happens to wind farms in South Australia – to protect the grid.

But they and other energy market participants are taking steps to avoid having to do this. ACT and South Australia offer incentives to increase the take-up of batteries by solar households, but Emlyn Keane, Evergen’s chief executive, says there has to be more to it than that.

“There has to be an end game, and the end game is you are giving relief to the grid,” Mr Keane says. “Behind the meter” or distributed energy resources are forecast to boom over the next two decades. Evergen is seeking a new major shareholder, Street Talk reported, to help it bring the technology to the mass market. 

Evergen’s software makes use of five-minute weather forecasts to optimise the household’s use of energy from solar panels, battery or grid. For example, if it’s going to be warm but cloudy, the system will charge the battery from the grid overnight at off-peak rates to be ready for the afternoon’s air conditioning load. 

Load control

The next frontier is “load control” – managing energy-hungry appliances so as to reduce grid usage at times of high demand. These practices – also known as “demand response” – can be done at industrial level as well as by aggregating household energy resources.

“People like Evergen have the ability to control, modulate and create a whole new business model for energy,” Mr Keane says. 

The system in the Zimmermans’ house is larger – 5.7kW of solar panels and a 17kWh battery – and has more sensors and smart functions than a standard Evergen system, which includes 5kW of solar and an 11.5kWh battery for about $17,000. If the sun is out and a room is heating up, the blinds close automatically. 

But the Mirvac energy-smart house aims to replicate a typical family’s lifestyle without being too futuristic, so that it can eventually be included in a standard design. 

What impresses Lisa Zimmerman is that her family can carry on as before, and the house runs efficiently – reducing costs and environmental impact – “without becoming overbearing or taking over your life”. 

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