Vehicle to grid or home battery, which is best for blackout protection?
With more Australian households installing solar and switching to electric vehicles (EVs), a common question arises: Should I get a home battery, rely on my EV for blackout protection through Vehicle-to-Grid (V2G) technology, or consider both?
While each option has its pros and cons, combining both could offer the most reliable and flexible solution. Let’s explore each in detail to help you decide what’s best for your home.
Use Case and Energy Needs
To begin, let’s assume your home already has a decent-sized rooftop solar system—typically in the 10 kW or larger range. This size of system is increasingly common in Australia and is more than capable of generating excess energy during the day, particularly in sunny regions. The question now becomes: what’s the best way to store and use that energy?
A stationary battery is designed to store excess solar energy and deliver it when needed, typically during the evening, at night, or when there’s a blackout. It’s always on-site, always connected, and always ready to respond.
On the other hand, a V2G-capable EV can also act as a home battery, discharging power back into your home or the grid. But this only works if your vehicle is at home, parked, and plugged in.
If your EV is regularly away during daylight or evening hours, such as during school runs, work, or errands, then it might not be a reliable backup source. In this case, a stationary battery is more dependable for managing your household’s energy needs.
Battery Wear and Tear
All batteries degrade over time through a process known as cycling, charging and discharging energy repeatedly. The rate at which a battery degrades depends on how deeply and how quickly it is charged or discharged.
Stationary batteries are designed for this kind of regular cycling. They typically discharge slowly and avoid running down to zero, which helps preserve battery health. These systems are engineered for consistent, steady use and are covered by warranties that account for frequent deep cycling.
EV batteries, by contrast, are built primarily for driving. Using them for V2G—where the car frequently charges and discharges into your home—may increase wear and tear. While some newer EVs are being designed with V2G in mind, not all manufacturers support this use, and some may limit or void the battery warranty if V2G is enabled.
In short, if you’re concerned about battery life or want a system that’s designed for regular power cycling, a stationary battery remains the safer option.
Hardware Compatibility and Integration
Installing a stationary home battery is relatively straightforward and widely supported by solar installers across Australia. These systems are typically plug-and-play with your rooftop solar, making integration smooth and reliable.
Setting up V2G is more complex. You’ll need:
- An EV that supports bidirectional charging (not all do)
- A V2G charger, which currently costs around $2,000 to $3,000
- A local electricity company or energy retailer that supports V2G programs
As of today, V2G support is still limited in Australia. Few electricity companies have rolled out full-scale support, so the technology remains somewhat early-stage. If your car and energy retailer are not yet V2G-ready, a stationary battery will be far easier to install and use straight away.
Cost and Return on Investment
Stationary batteries cost anywhere from $8,000 to $15,000 installed, depending on brand and capacity. However, rebates and subsidies, such as those available through state or federal renewable energy programs, can significantly reduce your out-of-pocket cost.
If you already own a V2G-compatible EV, it might seem cost-effective to simply use that battery. The charger is cheaper than a home battery—typically around $2,000 to $3,000—but remember: this only makes sense if your car supports V2G and your electricity company offers a program that allows it.
In terms of return on investment (ROI), stationary batteries save you money by using stored solar energy during peak times and reducing your reliance on the grid. V2G, when available, may go a step further by actually paying you for sending power back to the grid during peak demand.
Virtual Power Plants (VPPs): A Way to Earn from Your Battery or EV
An emerging opportunity in Australia is joining a Virtual Power Plant (VPP)—a program where your home battery and/or V2G-capable EV can participate in the electricity market.
Retailers like Amber Electric and some government-backed programs allow households to connect their energy storage systems to a wider network. When electricity demand is high (and prices spike), the VPP can discharge some of your stored energy back to the grid, either from your home battery or your EV.
In return, you’re paid a premium for that exported energy. This creates a new income stream and helps stabilise the electricity grid by providing extra capacity during peak times or emergencies.
If you already have a decent solar system and either a battery or a V2G-compatible EV (or both), enrolling in a VPP could make your setup even more valuable. You’re not just reducing your own bills—you’re also supporting the broader energy system and getting paid for it.
Not all regions or energy companies offer VPP programs yet, but availability is growing quickly. It’s worth asking your energy retailer or installer whether VPP participation is possible with your setup.
Environmental Impact
From an environmental point of view, both options help reduce emissions by allowing you to store and use your own solar energy rather than drawing power from the grid.
V2G stands out as more efficient in resource use because it repurposes your EV battery rather than requiring new battery materials for a separate home unit. This aligns with the idea of a circular economy—getting more use out of what you already have.
Stationary batteries, while requiring additional manufacturing, play an important role in shifting household energy use away from fossil fuels and towards renewables. When installed alongside rooftop solar, they help reduce your carbon footprint and provide reliable storage without needing your car to be home.
Participating in a VPP further enhances your environmental impact by helping to stabilise the grid and reduce the need for fossil fuel-powered peaking plants during high-demand periods.
Support from Power Companies and Energy Retailers
This is where things often stall for V2G in Australia.
V2G only works if your energy company allows you to discharge energy back into the grid and compensates you for it. Not all power companies offer this yet, and where they do, it may be part of a limited trial or require special equipment.
Stationary batteries, on the other hand, don’t rely on external programs to deliver value. Whether or not your energy company supports energy exports or incentives, a battery can still help reduce power bills, cut peak usage, and provide critical backup during outages.
With both V2G and battery systems, participation in a VPP—where available—offers an additional path to monetise your stored energy while supporting the grid.
Final Recommendation: Why Having Both Might Be Best
If your main goal is to protect your home from blackouts while also making the most of your solar power, having both a home battery and a V2G-capable EV offers the best of both worlds.
With a 10 kW+ solar system already in place, you’re generating a substantial amount of renewable energy each day. That energy can be used to charge your home battery and top up your EV—essentially giving you free fuel and stored energy from the sun.
At night or during a blackout, you have two power sources to draw from. If your car is away or needs its full range, the home battery steps in. If both are available, you can intelligently decide how to use or store your energy to maximise savings and flexibility.
Also, if you’re eligible for a VPP program through your energy retailer, you can now go a step further: earn money by allowing the grid to draw on your stored energy during peak demand. This applies to both your battery and your EV, turning your home into a mini power station that gets paid to help.
In summary:
- If you want immediate, reliable blackout protection, a stationary battery is your best bet.
- If your EV is V2G-ready and your electricity company supports it, it can reduce energy costs and add value.
- If you’re looking for the most resilient and future-ready setup, combining both gives you the ultimate flexibility, independence, and value.
- And if you can join a VPP, you may be able to earn money and help power a cleaner, more stable electricity grid.
Let your roof generate the power, your battery store it, and your car and VPP connection carry it into the future.
