Electric Hot Water System VPP Trial In South Australia

Solahart electric hot water system VPP trial

Image: Solahart

The Australian Renewable Energy Agency (ARENA) has announced funding for Rheem’s Active Hot Water Control project in South Australia. The trial involves storing excess solar electricity – both self-generated and from the grid – using thousands of electric hot water systems.

An electric hot water system can be considered an energy storage device as electricity is used to heat water stored in a tank for later use. Water heating is an energy-intensive process, accounting for around 25% of electricity consumption in households where electric hot water systems are used.

As hot water is generally used at home in the mornings and late afternoon and evenings, much of the electricity consumed for heating water will likely be drawn from the grid even if a home has solar panels installed.

This is where a PV hot water diverter can be beneficial. It’s a device that can be used with an existing electric hot water unit that enables surplus solar electricity to be diverted to the electric hot water system – you can compare a selection of these devices on SolarQuotes’ PV diverter comparison table. Other devices include “smart” relays, such as the Catch Solar Relay; but dedicated hot water diverters are probably a better option due to the way they operate.

In terms of the grid, while it was once more efficient to heat water during the night when overall demand was low, cheap surplus electricity is increasingly available during the middle of the day thanks in part to the rise of rooftop solar power systems.

South Australia’s wholesale electricity prices are now the lowest in Australia due to the state’s high level of renewables. In fact, South Australia is tussling with the challenges of so much rooftop solar electricity being generated in the middle of the day.

As well as providing benefits for solar households, smarter utilisation of electric hot water systems could improve renewable energy hosting capacity of networks, system stability and power quality.

Rheem’s Active Hot Water Control VPP Trial

In Rheem’s trial under its Solahart brand, approximately 2,400 residential households in South Australia with and without solar panels will be involved. The households will have Solahart Powerstore installed – a “solar smart” grid interactive, electric water heater – along with a home energy management system (HEMS).

The Powerstore systems will form a Virtual Power Plant (VPP) to participate in electricity price arbitrage, demand response, and other network services.

“By aggregating and optimising the energy use of hot water systems and other household appliances, VPPs could play a major role in managing system stability and reducing power bills for customers in South Australia and nationally,” said ARENA CEO Darren Miller.

Households participating in the trial will be rewarded and incentives required for customer participation will be tested across solar and non-solar homes, as well as across different socioeconomic groups.

The $9.9 million trial (put at $8.8 million on ARENA’s Active Hot Water Control project page) is receiving $1.9 million in funding from ARENA, a figure that is being matched by the South Australian Government.

“Australia is experiencing a solar installation boom which is driving the creation of record new renewable capacity,”  said Federal Minister for Energy and Emissions Reduction Angus Taylor. “This project will help South Australia to get the most out of this boom and maximise the use of renewables in the grid, reducing pressure on the electricity system.”

Further details of Rheem/Solahart’s Active Hot Water Control project are yet to be announced, but one of the partners noted is electricity retailer Simply Energy.

About Michael Bloch

Michael caught the solar power bug after purchasing components to cobble together a small off-grid PV system in 2008. He's been reporting on Australian and international solar energy news ever since.


  1. Maria Gardiner says

    I received an email today from SolarHart/Rheem saying send us your phone number and our persuasive sales consultant will ring you and talk you into participating in our Electric Hot Water System VPP Trial. Well it didn’t say that exactly – that was more the subtext. I couldn’t find anything on their website – just lots of promises that i would be happy and save lots of money. Do you know anything about the financials and benefits of being in this VPP? I did what they said and sent them my details but I always like to have info before i talk to sales consultants.

  2. Michael Noonan says

    Does anyone have any information on how well the Solahart Powerstore works or progress of the SA VPP Trial?
    Thinking og buying one but vant find many reviews.

    • Ronald Brakels says

      Because the Solahart Powerstore is new, I don’t have any information on how well it works yet. But it’s basically a PV hot water diverter. If you have an existing electric hot water system you can get a PV hot water diverter installed that should do the same job. Catch Power Green is one example that I wrote about it here:


      • Hi, has anyone looked into this further? The Solahart Power Store is more than just a electric hot water heater. If what their brochure says is correct it looks very good but I am just a person looking for the best solution to get rid of gas hot water in my house in Albany Western Australia and have no expertise in anything to do with this.

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