Solar PV systems are already commonplace and affordable in Australia, and battery storage is getting there quickly as well. Increasingly, Australia’s solar homes are looking for ways to maximise the value that solar & storage are able to deliver.
Home energy management systems (sometimes referred to as EMSs or HEMS) are fast becoming a popular way to get the most out of solar panels and batteries. To date, we haven’t seen a side-by-side comparison of the various offerings available in Australia. In the interest of bringing some transparency to this burgeoning market, we’ve reached out to a number of prominent EMS manufacturers for details on their products – and have compiled the results into the table below.
Image via nce.ncsu.edu
While the list may not be exhaustive, we’re confident that it contains most of the high-profile solutions currently on offer. (And if you see something missing, please email firstname.lastname@example.org.)
Also note that all the details included in the table were provided by the manufacturers themselves, so while they be accurate, they have not been independently verified by Solar Choice – we’re taking them at their word.
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The two primary functions of an EMS
On a basic level, an EMS does two things:
- Monitoring: An EMS allows you to see how energy is being used or generated in your home; at the very least you’ll see how energy is being used right now, but virtually all EMSs will also display historic data on demand. Ideally, an EMS will allow for monitoring of home energy consumption, solar and batteries, but in some cases the system may only provide monitoring for one of these three key elements.
- Control: An EMS should be able to control at least one element of the energy flows within your home. On one end of the spectrum, this could be as simple as enabling the user to switch devices on and off with an app, or as advanced as a sophisticated algorithm that automatically manages energy use within the home while also maximising the value of solar & stored energy with tariff arbitrage and tariff use optimisation.
We’ve used a very loose definition of energy management system for this article; some of the solutions included are primarily monitoring platforms with the potential to be fitted out with control functionality in the future. Some of them are inverters which act primarily as solar & battery managers, while others are full-fledged HEMSs that can function in the absence of solar or batteries; others are bolt-on devices that can be installed alongside a battery bank or on the home’s switchboard.
A helpful glossary of terms used in this table:
- Communications protocols & standards – Various ‘smart’ household devices may adhere to or use different communications standards; these standards include
- EEBus – A wireless communications protocol for electronic/IoT devices
- GSM – A telecommunications standard for mobile devices (allows your EMS to communicate over a wireless network)
- Modbus – A wireless communications protocol for electronic devices
- RS485 – A wireless communications protocol for electronic devices
- ZigBee – A wireless communications protocol for electronic/IoT devices
- Z-Wave – A wireless communications protocol for electronic/IoT devices
- DRED (Demand response-enabled device) – Devices such as air conditioners and refrigerators with DRED functionality can be remotely and/or automatically controlled to either switch off or use less energy in order to curtail energy consumption during peak pricing periods or when no solar is available.
- Internet of Things (IoT) – “the interconnection via the Internet of computing devices embedded in everyday objects, enabling them to send and receive data.”
- Peer to peer trading – The ability to sell excess (exported) solar or battery energy to other households. (A ‘moderator’ – usually an electricity retailer – is necessary for peer to peer trading to be possible.)
- Spot price trading – The ability to access the wholesale electricity spot market price on the National Electricity Market (NEM) in order to take advantage of high price events (See: Diamond Energy/Reposit Gridcredits).
- Tariff arbitrage – Leveraging the difference in TOU billing schedules to maximise energy bill savings
- TOU – Time of use billing, where grid electricity costs a different amount depending on the time of day it is used
- Virtual power plant – “A virtual power plant (VPP) is a system that integrates several types of power sources, (such as microCHP, wind-turbines, small hydro, photovoltaics, back-up gensets, and batteries) so as to give a reliable overall power supply.”
Energy management systems: A quick comparison
This table will be updated with more details as we become aware of them, and as new products come onto the Australian market.
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Where does AWS SunnyMate fit into this?
Is Reposit the most appropriate to use to direct surplus from the solar to the hot water element?
(I have solar tubes and a tank with an element half way down, so using surplus energy in winter does not limit the functioning of the solar tubes which draw water from the bottom of the tank.)
Good question, Ray – solar diverters could be classed as energy management systems themselves according to the very loose definition that we use here. The main difference is that EMSs usually have a digital monitoring component with an interface visible to users, while a solar diverter will usually function ‘behind the scenes’ without the ability to see how it works (some diverters are exceptions to this, of course). A number of the EMSs that we’ve included here also have a diverter function, and if prices are comparable then it probably makes sense to go with a diverter-equipped EMS than a diverter on its own.
We don’t recommend a particular EMS over any others, but instead have put together this table to help customers to make their own decisions. We encourage you to chase up as many of them as you think could be viable for you. In the meantime, we’ll also aim to expand our understanding of how each of them works in order to give more detailed responses in the future.
Hi very topical subject. Have you come across any info as to what capability the Powerwall 2 battery storage will include or support. I note they refer to the gateway not sure if it’s an option or not or what it does. A conversation with the Tesla rep when they called a month back didn’t have any idea regarding this.
Thank you for your comment. It would be best to speak with someone from Tesla directly as they have all the technical information as this stage we do not have any further information. You can contact Tesla through their Australian site https://www.tesla.com/en_AU/energy
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