TL;DR: Australian homeowners with solar batteries primarily use two strategies for return on investment: saving money by maximising self-consumption and reducing grid reliance, or making money by participating in Virtual Power Plants (VPPs) and selling stored energy back to the grid. The best approach depends on your household's energy usage, local electricity tariffs, and appetite for active grid participation.
How does maximising self-consumption save you money?
Maximising self-consumption uses your solar battery to store excess daytime solar power, then uses that stored power during the evening or morning instead of buying electricity from the grid. This strategy directly cuts down your electricity bill, which often gives the most predictable financial benefit for typical Australian households. Most electricity retailers charge between 25-40 cents per kilowatt-hour (c/kWh) for grid power, especially during peak evening times. In contrast, they pay very little for solar exports, with many feed-in tariffs now sitting below 8c/kWh. By consuming your own stored solar power, you avoid paying those high import charges.
Think of it this way: every kilowatt-hour (kWh) you pull from your battery instead of the grid saves you 25-40 cents. If your 10kWh battery allows you to avoid importing 8kWh from the grid each evening, that's a saving of $2.00 to $3.20 per day. Over a year, this adds up to between $730 and $1,168. This strategy works best for households with significant evening power use, like families running air conditioning, cooking, or watching TV after sunset. It ensures you get the maximum value from your solar generation by avoiding high retail tariffs.
What is the optimal battery size for self-consumption savings?
The optimal battery size for self-consumption directly matches your typical evening and overnight electricity consumption that your solar system cannot cover directly. For many Australian homes, a 10-13.5 kWh battery, such as a Tesla Powerwall 2 or an LG Chem RESU 10/13, works well. If a household uses 15-20 kWh per day, and their solar system generates 30 kWh, but they only use 5 kWh during the day, they have 25 kWh of excess. If their evening usage is 10 kWh, a 10 kWh battery prevents them from importing that power. Over-sizing a battery for self-consumption offers diminishing returns because you might not fill it daily, or you might not have enough evening demand to drain it, leaving capacity unused.
Can you make money by exporting power from your solar battery?
Yes, you can make money by exporting power from your solar battery, primarily through participation in Virtual Power Plants (VPPs) or by selling power when grid prices are favourable. This strategy involves a more active engagement with the electricity market compared to simply reducing your own bill. VPPs, offered by various energy retailers and technology providers, link a network of home batteries to act as a single, larger power source. When the grid needs extra power, especially during peak demand or system instability, the VPP can draw power from your battery and export it. In return, you receive payments, credits, or other incentives from the VPP operator.
The amount you earn varies significantly. Some VPP programs offer a fixed annual payment, for example, $100-$300 per year, regardless of how often your battery exports. Others operate on a dynamic model, paying you per kWh exported during specific events. This second model relies on your retailer or VPP provider optimising export times to maximise profit during high wholesale prices. This strategy requires a smart inverter and compatible battery that can communicate with the VPP network, and often involves giving the VPP operator some control over your battery's discharge cycles.
How do Virtual Power Plants work with battery exports?
Virtual Power Plants (VPPs) aggregate the storage capacity of many household batteries to create a collective power resource. When the grid experiences high demand, such as during a heatwave, or when a traditional power plant unexpectedly goes offline, the VPP operator signals the connected batteries to discharge power back into the grid. This helps stabilise the network and provides a valuable service to the energy market. Homeowners participating in VPPs benefit by receiving financial incentives, often as a direct payment or a credit on their electricity bill. For instance, in 2023, AGL's VPP program paid some customers up to $200 per year in bill credits for allowing their battery to be dispatched. This provides an additional revenue stream beyond standard feed-in tariffs.
Which strategy offers a better return on investment for solar batteries?
Deciding whether saving money through self-consumption or making money via VPPs offers a better return on investment (ROI) depends on individual circumstances and priorities. For most Australian households, maximising self-consumption provides the most consistent and predictable financial benefit. The savings from avoiding grid purchases at 25-40c/kWh generally outweigh the earnings from current VPP programs or standard feed-in tariffs (3-8c/kWh). A typical 10kWh battery costing $10,000-$15,000 installed could save a household $700-$1,200 annually by avoiding grid imports. This often leads to a simpler payback calculation and a clearer path to ROI.
However, the "making money" strategy through VPPs can add extra value, especially if your household already minimises grid imports. VPP payments often act as a bonus on top of your self-consumption savings. As energy markets evolve and VPP programs mature, the financial incentives for exporting power may increase, potentially shifting the balance. Currently, few VPP programs offer enough incentive to make active grid participation solely profitable without also considering the self-consumption benefits. It is crucial to evaluate the terms of any VPP offer, including how often your battery may be discharged, potential impacts on battery lifespan, and the actual financial return.
Why is household energy use a major factor?
Household energy use patterns dictate which strategy gives the best ROI. If your household uses most of its electricity in the evening after the sun goes down, a self-consumption strategy is usually superior. A battery stores the solar power generated during the day, which you then use when grid prices are highest. This directly reduces your electricity bill, saving you the difference between your import tariff and your feed-in tariff. If your household's daytime power consumption is high, and you have little excess solar to store, a battery for self-consumption offers less benefit. Conversely, if you have a large solar system and significant excess power even after meeting your own needs, participating in a VPP might become more attractive, as you have more capacity to export to the grid for payment. Understanding your specific daily load profile is critical for accurate ROI calculations.
Key Takeaways
- Prioritise self-consumption first: Most Australian homes get the best ROI by using stored solar to avoid high evening grid charges (25-40c/kWh).
- Evaluate VPPs as a bonus: Virtual Power Plant payments (often $100-$300/year) add to savings but rarely justify a battery on their own.
- Match battery size to your usage: Size your battery based on your typical evening and overnight power consumption for optimal self-consumption.
- Understand your electricity tariffs: High import tariffs and low feed-in tariffs strengthen the case for self-consumption.
- Review VPP terms carefully: Understand how often your battery discharges, the payment structure, and any impact on battery warranty before joining a VPP.
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